BG112555A - Method for evaluation and control of the porous media supplyability to plasma-aided through activation technological processes - Google Patents

Abstract

The invention relates to a method for evaluation and control of the porous media susceptibility, for example, wood, cellulose, polymers, textiles and products thereof, to an assisted technological processes by preliminary plasma surface activation (functionalization, oxidation), and in particular of plasma-aided surface impregnation outside the technological line, which includes increasing the free surface energy by processing the surface, directly or remotely, with nonthermal cold plasma of a dielectric barrier discharge in air at atmospheric pressure, and reducing the surface tension of the impregnating solution with the help of surface-active agents, so that the difference between the obtained free surface energy and the surface tension of the solution to be a positive value - as greater as possible. The dielectric barrier discharge burns in a two- or three-electrode system, supplied with alternating voltage, at industrial frequency - 50 or 60 Hz, or increased frequency - up to 1 kНz, as the value of the voltage on the discharge gap, with size from 3 to 24 mm, is between 10 kV rms (amplitude 11.4 kV) and 42 kV rms (amplitude 59 kV), i.e. it burns in streamer mode, and the technology is microplasma activation technology. 10 claims, 24 figures A declaration of license readiness has been submitted in accordance with Art. 30 of the Law on Patents and Utility Model Registration.

Description

METHOD FOR ASSESSING AND CONTROLLING THE SUSCEPTIBILITY OF POROUS MEDIA SUPPORTED BY PRIOR PLASMA SURFACE ACTIVATION TECHNOLOGICAL PROCESS

Field of application

The invention relates to a method for assessing and managing the susceptibility of porous media, for example, wood, cellulose, polymers, textiles and products thereof, to a prior plasma-surface activation (functionalization, oxidation) assisted technological process, and more specifically of plasma-assisted off-line surface impregnation, which involves increasing the surface free energy by treating the surface, directly or indirectly, with non-equilibrium (cold) plasma of a dielectric barrier discharge in air (DBR), at atmospheric pressure and room temperature, and reducing of the surface tension of the impregnating solution with the help of surfactants (surfactants), so that the difference between the acquired free surface energy and the surface tension of the solution is a positive value - preferably greater.

The method extends the application of microdischarge plasma-chemical technologies for surface activation of porous media, since the barrier discharge burns in streamer mode - it is cathodically or anodically directed streamers forming a spatial matrix of microdischarges randomly distributed in the discharge gap.

The method expands the application of plasma-assisted technological processes taking place in air, at atmospheric pressure, ambient temperature and humidity, bringing them "outside the technological line" (or on site at the customer) painting, printing, varnishing, lamination, foiling, lamination, impregnation and others.

The method significantly extends the protection against flaming combustion of porous materials and their products by creating a protective diffuse coating by impregnating them with aqueous solutions of flame retardants - the elements of the interior and interior furnishings of the home, office, office buildings, public buildings, concert and sports halls, theater halls and stages; staging technique in cinema, theater and television, hotels, restaurants and discotheques; the interior of means of transport - ships, planes, trains and cars; building materials and architectural-building elements - boards, beams, plywood, wooden boards, fences, paneling, floor, walls, building elements of houses; packaging materials cardboard, paper, corrugated cardboard, foils, etc.

Prior art

Plasma-assisted technologies are known, which use preliminary plasma-chemical surface activation of porous media, such as wood, cellulose, foamed polymers, textiles, of materials and products based on them, in air, at atmospheric pressure, ambient temperature and humidity, for application of decorative, protective and functional adhesive and diffuse coatings - varnishing, painting, gluing, foiling, lamination, lamination, printing and impregnation. The result of the preliminary plasma-chemical activation is expressed in: a) a change in the chemical composition of the surface at a depth of 5-^10 psh and the appearance of a large amount of oxygen-containing groups, including hydroxyl ones; b) increase of the free surface energy, as a result of the increase of its polar component; (c) increasing surface polarity; d) enhancement of the cationic character of the activated surface; and as a result of all this increase the capillary, chemical and ionic activity of the porous surface.

A method is known for preliminary plasma-chemical surface activation, functionalization or oxidation, of porous media, to support or improve their surface impregnation with aqueous solutions of flame retardants, including the direct treatment of the surface with non-equilibrium (cold) plasma of a dielectric barrier discharge in air under normal conditions - atmospheric pressure, room temperature and humidity; and/or the indirect (indirect) treatment of the surface by means of a jet or flow of air passing through a semi-open plasma system, carrying discharge products - gases, vapors and chemically active particles (CHAP), WO 2006133524 A2 (WIPO; BG; 2005).

An alternative embodiment of this method involves purposefully changing the ionic activity of the nonionic impregnating solution containing 30 wt. % dry substance (phosphoric flame retardants), before impregnation, adding surfactants (surfactants) - non-ionic, anionic and/or cationic. The choice of surfactant is made on the principle of ion charge neutralization, after checking the acquired ionic activity of the plasma-activated surface, i.e. impregnation is carried out with an anionic impregnating solution if the surface has acquired cationic activity, or vice versa - with a cationic impregnating solution if the surface has acquired anionic activity. Thus, in practice, a single highly efficient plasma-assisted 2 impregnation process is realized, which includes both the plasma-chemical activation of the porous surface and the modification of the impregnation solution in accordance with the change. Nowhere, however, does it speak of susceptibility of the activated surface to the next assisted process - surface impregnation, and even less is it related to the free surface energy acquired after plasma activation and to the surface tension of the impregnating solution. It is not a question of assessing this susceptibility, much less of managing the susceptibility to maximize the effect of surface impregnation.

The described method of plasma-chemical surface modification of porous media to improve their impregnation with aqueous solutions of flame retardants is distinguished by improved manufacturability, applicability, universality, reliability and speed of action. It can be applied "off-line", i.e. at the customer's place, regardless of the geometry and dimensions of the processed article and the accessibility of the surfaces from which it is composed - ceiling, vertical and/or horizontal surfaces.

The main disadvantage of the mentioned plasma-assisted technologies consists in the fact that the plasma-assisted impregnation is not consistent with the results of the preceding plasma-chemical surface activation of the porous medium. Most often, in these cases, the plasma-chemical activation of the surface and its subsequent process are not considered as a single technological process that must be adequate, predictable and manageable in order to purposefully and efficiently achieve better results. Performance indicators of plasma activation are sought separately, rather than indicators that define the entire plasma-assisted process.

In essence, plasma support of technological processes is expressed in their improvement. Therefore, one should speak, with equal justification, of "plasma-assisted and "plasma-enhanced technologies or technological processes. The applicability of plasma-chemical surface activation to a particular technology only makes sense if it leads to better results after the integration of the two processes. Plasma-chemical surface activation is a technology that allows control of the surface properties of porous materials, within certain limits, thereby changing/improving the susceptibility of the material to the next "plasma-assisted" technology. Thus arises the necessity, this acquired susceptibility of the material of the next (assisted) process to be evaluated and on this basis purposefully managed.

The known method of plasma-chemical modification of porous media to support the impregnation process, however, does not address the question of assessing the acquired susceptibility of the impregnation medium, after the preliminary plasma activation, and even less of managing this susceptibility. Only the means/tools for improving the susceptibility of the porous medium, the prior direct or indirect plasma-chemical surface activation and the use of surfactants to modify the impregnating solutions are shown.

It is known that porous materials, such as wood, exhibit the so-called surface inactivity, as a result of contamination of the surface with hydrophobic substances during their thermal and mechanical processing. The inactive wood surface is poorly wetted and does not lend itself to printing, coating, painting, gluing, lamination and impregnation. Such a wooden surface refers to the so-called low-energy surfaces that have low free surface energy: os < 35 mJ/m ² , weak polarity and a large equilibrium contact angle of wetting: (70° < Θ < 90°). For cellulose and cellulosic materials, this limit is known to be up to 42 mJ/w ² . The preparation of the surface, in this case, is extremely imperative and includes, in addition to cleaning the surface, its mandatory activation, which makes it a high-energy surface (os> 38 or 42 mJ/m ² ), improving its susceptibility to the next technology.

It is well known that surface activation by flame and plasma processes reduces the equilibrium wetting contact angle and increases the surface free energy. The notion of free surface energy is usually introduced by the well-known Young's equation, which describes the equilibrium of stresses at point A, at the boundary between the three phases - solid, liquid and gas (vapor), fig. 7:

osl = os- уь cos θ. (1)

The balance between the three interphase tensions (energies): os - the tension between solid and liquid phase or the free energy of the solid surface, mN/m or mJ/m ² ; уь - the tension between liquid and gas phase, mN/m or mJ/m ² ; osl - the tension between solid and liquid phase or the interfacial energy, mN/m or mJ/m ² , determines the equilibrium (static) or simply contact wetting angle Θ, which can be measured by the well-known stationary drop method.

In order to distinguish them better, further on in the exposition, the following names and units of measurement (SI) are used unambiguously here: for as - free surface energy, mJ/sh ² ; γη - surface tension of the liquid phase, mN/m; osl - interphase energy, mJ/m ² . Since surface tension has a very small value, it is still in practice in some countries and companies to use the unit "dynes per centimeter" (CGS), dyn/cm: for example, the surface tension of distilled water at 25 °C is 72 dyn/ cm or 72 mN/m (72. Ju ³ N/m).

Complete wetting of the surface should occur when the interfacial energy osl becomes zero, i.e. the contact angle Θ also becomes zero: Θ = 0; cos Θ = 1. Complete wetting can be observed when the surface free energy as becomes equal to the surface tension yi. of the liquid: as = Π, [3].

In the practice of finishing surface technologies of foil packaging materials (based on polypropylene, polyethylene), the complete wetting of the surface, after plasma-chemical activation, is perceived as a prerequisite for an effective assisted subsequent process - printing, gluing, painting, lamination, laminating.

On this basis, rules of thumb have been developed for the efficiency of finishing plasma-assisted technological processes, mainly in the processing of thin films and foil materials, in the packaging materials industry. Here's a rule of thumb for efficiency formulated by Webconvert, Canada: "If the liquid has a surface tension u/. less than the free surface energy of the substrate as: уь < os, then the liquid will spread in a continuous layer on the surface. If the surface tension of the liquid уй is equal to or greater than the free surface energy as, yr > as, then the liquid will be firmly connected to the surface and form separate drops" [3].

The company "Velaphone A/S", which has been on the market since 1951, also formulated, based on its many years of experience, the following general rule of thumb for the effectiveness of plasma preactivation: "Oedipus material will become wet if its free surface energy as is greater than the surface tension of the liquid eq. as > ух, [4].

The Kruss company, however, warns that the contact of the activated surface with the transport rollers and other untreated plasma surfaces on its way in the technological line leads to the so-called aging of the activated surface, i.e. it loses its activity, and the reduction of the free surface energy as can reach 10 mJ/sh ² . Therefore, the general rule should undergo the following correction: "In general, the surface free energy as of the film (foil) should be greater than the surface tension уй of the ink by between 3 and 10 mJ/m ² to ensure an acceptable result of what was done: as> уь+ 10, mJ/m ² ", [2].

Three approaches are known to determine the efficiency of the surface plasma chemical process, which use the wetting contact angle and/or the surface free energy of the activated surface as an indicator of the change/efficiency.

The first of the known methods is based on the fact that distilled water is widely available as a control or test liquid, it has the highest surface tension of all solvents used in practice - 72.86 mN/w (at 25 °C), so if it wets the surface, then all other solutions with lower surface tension used will wet it. On this basis, methods have been developed and standardized for evaluating the effectiveness of plasma-chemical surface activation by measuring the static contact angle of wetting of a stationary drop of (distilled) water placed on the surface of a corona (plasma) or flame treated polymer film ( varnish, paint, hard surface): ISO 15989:2004-12; ASTM D5946:2009. It is also known that hydrophilic surfaces have a high degree of wetting - 10° < θ< 30°, and super-hydrophilic surfaces have an ultra-high degree of wetting - 0 < 5°.

Other test fluids whose surface tension is well known are also used, for example, ethylene glycol: 47.3 mN/m (25 °C), metal iodide: 67 mN/m (25 °C), which allow, in the same way, to estimate the wettability of the solid surface. The condition for complete surface wetting, however, is often fulfilled at lower values of the surface free energy than the surface tension of water, Fig. 22.

The method for quantifying the free surface energy after plasma activation uses the so-called a set (kit, set) of test inks. Kits of test inks are known (ASTM D2578:2009; ISO 8296:2006) which include a number of inks whose surface tension varies in the range of 30 to 70 mN/m, in steps of 1 or 2 mN/m (± 0.5 or 1.0 mN/m). Using them, for example, in increasing order, allows the surface energy of the activated surface to be determined. The surface energy is higher than the surface tension of the ink (as > γι) when the droplet spills over the surface for up to 3 seconds. The ink with the minimum value of this surface tension determines the surface energy of the activated surface. In cases where the ink does not wet the surface and forms drops, for up to 1 second, the surface energy is lower than the declared surface tension (as < ul). Such test kits are manufactured and implemented by numerous companies, such as Vetaphone A/S, Denmark; Softal Corona and Plasma GmbH, Germany; CDE Products, UV Dyne Testing Ltd. and Dyne Technology Ltd., UK; Process Supply, Inc., Jemmco LLC, Coatings Inc., Diversified Enterprises and Enercon Industries Corp., USA; Converting Supply, Inc. and Webconvert Ltd., Canada, which activate various films, most commonly polyolefins (PP·, PE). They are used in the form of drip, spread or spill inks, spreader pads and writing markers. The method for characterizing the change in free surface energy after plasma activation with the test inks is standardized: ASTM 02578:2009, ISO 8296:2006; GB/T 14216:1993.

The method with test inks is mainly used to determine the result of plasma activation of films and materials from polyolefins (polyethylene, polypropylene). This limitation makes it necessary to check the applicability of the method for any other material, since the obtained result may be too far from the actual value of the surface energy. The main disadvantages of this method are also due to the fact that the adequacy and reliability of the obtained results strongly depend on the differences in polarity, pH and solubility of the solid phase. The evaporation of the test ink, the microgeometry and roughness of the solid surface, the porosity and the presence of structural defects, the inhomogeneity and inhomogeneity of the surface, the presence of impurities on the surface, have an additional influence [2].

The third method for determining the free surface energy of the plasma-activated surface is associated with the use of a certain number of test liquids with known and different surface tension - two and/or three, which allows to determine the free surface energy of the activated surface and its components - polar and non-polar, via the equilibrium wetting angle, depending on the Zisman, Fowkes, OWRK, Schultz, Wu and equation of state (EOS) computational models and theories used. The measurement of the equilibrium contact angle of wetting is the basis of the computational models used to quantify the surface free energy and its change after activation, [1, 2].

The method of determining the free surface energy, with two/three liquids, is standardized and is used to determine the susceptibility of the activated solid substrate to the used paints, varnishes, liquids, foils and adhesives: DIN 55660:2012-2, DIN ΕΝ 828: 2013-04 (E).

The main drawback of the mentioned methods for evaluating the receptivity of the activated surface to the impregnating solutions, adhesives, paints, inks is that they are aimed only at revealing the result of the plasma activation of the solid surface - and that of a certain range of materials. In doing so, the goal is for the surface of the various types of polyolefins to acquire a high free surface energy, i.e. for it to become a high-energy surface, with a surface energy over 38 mJ/sh ² , table. 1.

Table 1.

Low energy insensitive surface (polyolefins): 6s <38 mJ/m ² Substrate - foils, coatings, films (polyolefins) - output surface Free surface energy, mJ/m ² (dyn/cm) Polypropylene (PP) 29 Low Density Polyethylene (PE-LD) 31 High Density Polyethylene (PE-HD) 32 Biaxially Oriented Polypropylene (Biaxially Oriented Polypropylene) 32 High-energy plasma-activated - receptive surface: 6s > 38 mJ/m ² Plasma-assisted process Required (recommended) free surface energy, mJ/m ² (dyn/cm) Printing - inks with organic solvents 38-44 Printing - water-based inks 42-48 Printing - UV crosslinkable inks 44-60 Lamination 42-54 Coating 46-56

The starting film has a low free surface energy, which varies within relatively narrow limits, depending on its nature, mJ/m ² : (29 - 32) < 38. The recommended, based on experience, values of the required (high) free surface energy energy range in a fairly wide range of values, depending on the subsequent plasma-assisted technological process, mJ/m ² : (38 -60), table. 1.

If the rule of receptivity of the inks (solutions, melts, glues) of the company "Kruss" is followed, then their surface tension should be lower by up to 10 mN/m of the free surface energy of the surface, i.e. from 28 to 50 mN/m. If, for example, inks based on organic solvents are used, their surface tension in most cases is below 30 mN/m, which means that the recommendation from table. 1 is adequate, but if water-based inks without surfactants are used, their surface tension will be over 60 mN/h, which cannot guarantee an efficient printing process. In this case, the tacit assumption that water-based inks contain surfactants, which reduces their surface tension to the required extent, is clearly relied upon.

In order to evaluate the susceptibility, not only of the plasma-activated, but also of any output surface, it is necessary to determine unambiguously both quantities - of the free surface energy of the substrate and the surface tension of the solution (ink, paint, varnish, melt), to be matched. Determining only the free surface energy of the plasma-activated surface does not allow to reliably predict the result, as well as to sustainably manage the integrated technological process.

In the cases of a real porous surface, the evaluation of the surface free energy is significantly complicated after plasma activation, since, in addition to roughness, polarity, contamination, chemical and geometric heterogeneity, the porosity of the medium is manifested here. At the beginning of the process, the spilling of the solution on the surface of the porous medium competes very strongly with the absorption (absorption, drainage) of the solution in depth. The change in wetting contact angle is due to simultaneous wetting and watering of the solution, i.e. this is the contact angle of both wetting and wicking. The use of the measured contact angle to calculate the surface energy according to the general methodology for dense surfaces must be made with the proviso that for porous surfaces, this is an apparent (effective) value. It is obtained by bringing the real change of the measured contact angle to a conditional change due solely to the spilling of the liquid on the surface, fig. 8.

It is known, not only from our own practice, that this approach works, but all empirically derived rules and recommendations for the surface treatment of foils, films and coatings cannot be transferred uncritically to porous media. Yes, plasma-assisted technologies are used for wood and its products, pulp, paper, cardboard, corrugated board, plywood, but there are no developed methods for evaluating, predicting, and managing the overall plasma-assisted process.

It is also known that the plasma-chemical activation of the surface of the porous materials has its maximum result immediately after the completion of the process. The chemically activated surface interacts not only with various inactive and contaminated surfaces, but above all with the surrounding air environment. Therefore, the newly activated surface has its maximum chemical, ionic and electrical (polarization) activity. From this point on, the surface undergoes continuous chemical change and reorganization, at first faster and then more slowly over time. This natural process of surface chemical conversion of the surface is accompanied by a continuously decreasing surface activity. It can be seen as a continuous aging process of the activated surface, as a result of which it gradually loses its activity. The free surface energy decreases, and after a certain time, characteristic of the porous medium, it can even get a value below that of the initial surface. The time characteristic that determines the time interval elapsed from the completion of the plasma activation process to the beginning of the assisted technological process is called the open (technological) time.

It is known that the aging of the activated surface can be avoided in a single way, when the plasma activation is incorporated in a process line where the open time becomes equal to zero, the assisted process follows immediately after the plasma activation. This is the main way in which modern plasma-assisted processes are carried out - «inside the technological line».

Very often, however, it is necessary to look for a finishing technology that will provide a significant change in certain quality indicators of an already created product or structure that is outside the production line. This could be, for example, a wooden building structure built on site at the customer's site, which needs to be protected from flame burning, rotting or insects by surface impregnation and application of the impregnating solution by brush or roller, by pouring or by pressure spraying. At the same time, surfaces that are located in a different way must be processed - floor (horizontal), vertical (walls) or ceiling. Plasma treatment of the entire surface, which can have an area of several to hundreds and thousands of square meters, requires a certain time. Usually this time is greater than the surface impregnation time. It is difficult, even impossible, to provide immediately, immediately after the plasma surface activation, the finishing process of impregnation. The entire area is plasma chemically treated, and only after that the impregnation process begins, i.e. a certain open time is required between the two processes.

The open time, however, determines the degree of aging of the surface, which can be quite different for different porous materials and the conditions under which they "wait" for impregnation. Therefore, the process of transformation (reorganization) of the activated surface must necessarily be included in this technological chain. In this case, it does not matter what the surface activity or surface free energy is immediately after plasma activation, but after a certain open time. Rapid aging is known to end after 20^-30 min, but within about two hours the loss of activity is still significant. Therefore, it can be empirically assumed that the minimum open time of two hours determines the aging of the activated surface and at the same time ensures the implementation of the multitude of plasma-assisted processes outside the technological line.

At the same time, the required level of surface activation can be maintained for a relatively long time, for example, one day or 24 hours. The open time of 24 hours can ensure the processing of any geometrically and spatially complex construction. Naturally, it is curious to estimate the critical open time, after which the plasma preactivation process loses its meaning, since its effect ceases to exist.

Therefore, when talking about evaluating and managing the overall plasma-assisted process, it is necessary to define/set the open time that is needed to synchronize the two processes - the preliminary plasma surface activation and the process of forming the protective coating by impregnation. The acquired free surface energy should be determined immediately after plasma activation and after the set open time. Essential technological information can carry the critical open time, that time after which the effect of plasma activation disappears.

It is also known that plasma-chemical activation can take place, either directly, in the cold (non-equilibrium) plasma of the electrical discharge burning in air, at atmospheric pressure, ambient temperature and humidity, or indirectly (remotely), with the products from this discharge, containing HAC, which are carried out of the discharge gap. The electric discharge is a dielectric barrier discharge that fires at voltages up to 30 kV rms and frequencies from 50 (60) Hz to 100 kHz, WO 2006133524 A2 (WIPO; BG; 2005).

It is also known that the higher the frequency, the higher the surface density of the active electrical power and the greater the amount of electrons and HACs that can cause chemical changes on the surface of the porous medium. Dielectric barrier discharge has a characteristic spatial structure, which includes randomly appearing at the same place, but also randomly spaced microdischarges. Each discharge itself is composed of multiple spatially oriented cathodic and anodic streamers with lifetimes of the order of tens and hundreds of nanoseconds. The homogeneity of the discharge is strongly dependent on the frequency, therefore it is recommended that the discharge be applied at frequencies above 1 kHz.

A major disadvantage of the dielectric barrier discharge at increased frequencies, from 50 Hz (1 kHz) upwards, is the complexity and cost of the technical means ensuring the existence and management of the discharge. It is also known that the energy of the active electrons decreases as the frequency increases. Special gas media (helium, argon, gas mixtures) are used, which create the so-called homogeneous discharge at atmospheric pressure (at about 1 atmosphere), but this is associated with extreme complication of the gas system of the plasma device. In addition to air, pure oxygen can also be used as a much more effective oxidizing medium. In this case, however, the complexity and cost of the plasma technological arrangement greatly increases.

Given the described known methods, the task of the invention is to propose a method for evaluating, predicting and managing the susceptibility of porous media to (plasma-assisted) technological processes by preliminary surface activation - functionalization or oxidation, and more specifically to plasma-assisted surface off-line impregnation to include an increase in free surface energy and a decrease in surface tension of the impregnating solution.

The impregnation susceptibility of the porous medium is estimated by the difference between the free surface energy and the surface tension of the impregnating solution. Control of compliance is accomplished by increasing surface free energy and decreasing surface tension so that compliance becomes a positive value, the greater this difference, the more amenable to the impregnation process the porous medium becomes.

The free surface energy of the pre-activated surface to be determined at the end of the open process time, characterizing the degree of manifested aging of the plasma-activated surface in air at atmospheric pressure, ambient temperature and humidity, so that the integrated process of plasma activation and surface activation can to be carried out outside the technological line. Surface plasma-chemical activation, to increase the surface free energy, to be carried out either by direct treatment of the surface with non-equilibrium (cold) plasma of a dielectric barrier discharge in air under normal conditions, and/or by remote treatment of the surface with products of discharge - gases and vapors containing chemically active particles.

The direct plasma-chemical surface treatment should be carried out bilaterally and continuously by the passage of the porous medium through the plasma of the discharge, inside the discharge space, while the thickness of the treated product cannot exceed the size of the discharge (air) gap. The remote plasma-chemical surface treatment with products from the combustion of the dielectric barrier discharge, distributed in a stream of air passing through the discharge gap, to be carried out unilaterally in a semi-open plasma technological system, so that part of the treated surface closes the active volume, and a semi-permeable partition (brush) to allow the continuous processing of the surface "step by step" by its relative movement with respect to the active volume.

The surface free energy to be determined by measuring the equilibrium contact angle by the stationary drop method with two or three liquids using known appropriate computational models and theory.

The surface tension of the impregnating solution should be reduced with the help of surface-active substances - first, by the independent use of anionic micelle-forming surfactants or in combination with neutral and/or amphoteric surfactants; second, by increasing the temperature of the impregnating solution. The surface tension of the solution is determined by measuring the equilibrium wetting contact angle using the hanging drop method.

Technical essence of the invention

The task of the invention is solved by a method for evaluating and managing the susceptibility of porous media to plasma-assisted technological processes, through preliminary surface activation - functionalization or oxidation, and more specifically to plasma-assisted surface impregnation, outside the technological line, i.e. after aging of the activated surface in air under normal conditions - atmospheric pressure, ambient temperature and humidity, including an increase in free surface energy by direct treatment of the surface in non-equilibrium (cold) dielectric barrier discharge plasma in air at atmospheric pressure and room temperature, and /or by remote treatment of the surface with discharge products - gases and vapors containing HAC, and reducing the surface tension of the impregnating solution with the help of a surfactant, characterized in that the susceptibility of the impregnation surface is estimated by the difference between the free surface energy determined at the end of the open process time, characterizing the degree of aging of the activated surface, and the surface tension determined after the addition of the surfactant, and the control of the susceptibility is carried out by the increase of the free surface energy after the preliminary plasma-chemical a activating and reducing the surface tension of the impregnating solution by using anionic micellar/aqueous surfactants alone or in combination with neutral and/or amphoteric surfactants, and/or increasing its temperature so that the difference is a positive value, where the more the larger this difference, the more susceptible the porous medium becomes to the plasma-assisted impregnation process.

A variant implementation of the method for evaluating and managing the susceptibility of porous media to plasma-assisted technological processes carried out outside the process line allows the free energy of the plasma-activated surface to be quantified by measuring the equilibrium contact angle of wetting by the method of the stationary drop, is two or three liquids, by the known computational models and theory used for ideal non-porous, smooth, solid, homogeneous and geometrically and chemically uniform surfaces.

Another variant embodiment of the method for assessing and managing the susceptibility of porous media to plasma-assisted processes carried out outside the process line allows the surface tension of the liquid to be quantified by measuring the equilibrium contact angle of wetting by the hanging drop method .

Yet another variant implementation of the method for evaluating and managing the susceptibility of porous media to plasma-assisted technological processes outside the technological process allows the increase of the free surface energy to be carried out by the direct treatment of the surface inside the plasma of a dielectric barrier, also called corona, smoldering, capacitive or silent discharge, for a time of up to 120 s, which burns in streamer mode - on cathode or anode directed streamers, forming a spatial matrix of microdischarges randomly distributed in the discharge gap.

A variant implementation of the method for evaluating and managing the susceptibility of porous media to plasma-assisted technological processes, outside the process line, allows the increase of the free surface energy to be carried out by indirect treatment of the surface for a time of up to 120 s with products of the combustion of a dielectric barrier a discharge in air under normal conditions containing chemically active particles, and the discharge also burns in a streamer mode and forms a spatial matrix of microdischarges randomly distributed in the discharge gap.

Another variant implementation of this method uses the microdischarge burning mode of a dielectric barrier discharge, which burns in a two- or three-electrode system, an alternating voltage is supplied at an industrial - 50 or 60 Hz, or increased - up to 1 kHz, frequency, such as the value of the voltage on the discharge (air, working) gap with a size of 3 to 24 mm is between 10 kV rms (amplitude 11.4 kV) and 42 kV rms (amplitude 59 kV).

A variant embodiment of this method uses surface direct plasma processing, which is carried out bilaterally and continuously by passing the porous trace through the discharge plasma, and the thickness of the processed product cannot exceed the size of the discharge gap.

Another variant embodiment of this method uses the remote surface treatment with products of the combustion of the dielectric barrier discharge, which are distributed in a flow of air passing through the discharge gap, to carry it out unilaterally, in a semi-open technological system, so that part of the treated surface closes the active volume, and a semi-permeable barrier (brush) allows the continuous processing of the surface "step by step" by its relative movement relative to the active volume, where the chemically active products are generated.

Variant embodiment of the method, according to which the open (technological) time is measured from the moment of completion of the plasma surface activation process to the beginning of the plasma-assisted impregnation process, for each part of the impregnated surface, and takes values from 2 to 24 hours, which allows the two processes to be effectively synchronized - the plasma pre-activation and the surface impregnation, while maintaining, to the required extent, the acquired improved surface compliance to the impregnation process.

Another variant embodiment of the method allows, by impregnating aqueous solutions of phosphoric flame retardants, the protective diffused coating produced to be observed optically, after the protective coating has developed by chemical transformation in the temperature range of 185 to 230 °C to form carbon black layer, which allows in turn to assess the thickness, integrity and defectiveness of the coating when making appropriate cuts - along the direction or across the structure of the porous medium.

The described method for assessing and managing the susceptibility of porous media to plasma-assisted technological processes carried out outside the technological line is distinguished by improved technological ability, applicability, universality, reliability and speed of action. It significantly expands the application of plasma-assisted technological processes outside the technological line. However, this does not mean that it cannot be used for the same purposes in carrying out this type of process in the classical way - in technological lines.

The proposed method for assessing and managing the susceptibility of porous media to plasma-assisted technological processes carried out outside the technological line allows the positive qualities of plasma-assisted technologies to be fully manifested, including the technologies for impregnation and application of protective solutions through dipping, pouring, pressure spraying or by roller or brush application. However, this does not mean that its application is limited, since it can be applied with the same success in other surface technologies - printing, painting, applying coatings and films, gluing, varnishing, laminating, laminating, etc.

Brief description of the attached figures

An exemplary embodiment of the method for evaluating and managing the susceptibility of porous media to pre-plasma-surface activation assisted processes is presented with the aid of the accompanying figures, wherein:

fig. 1 schematically presents the method for evaluating and managing the susceptibility of porous media of pre-plasma-surface activation-assisted technological processes, and more specifically of plasma-assisted surface impregnation, realized outside of a process line, when the open time is different from zero, t .is the plasma-chemically activated surface is subjected to aging before the assisted impregnation takes place;

fig. 2 schematically presents a variant of the method for evaluating and managing the susceptibility of porous media to technological processes assisted by preliminary plasma surface activation, involving only an increase in the free surface energy, implemented in a process line when the open time is equal to zero, i.e. the plasma-chemically activated surface is not subjected to aging before the assisted impregnation is carried out;

fig. 3 schematically presents a variant of the method for evaluating and controlling the susceptibility of porous media to assisted by prior plasma surface activation technological processes, in which the increase in the surface free energy of the porous media is achieved by direct microplasma treatment of the surface in a dielectric barrier discharge that burns in two-electrode (diode) plane-parallel (coplanar) asymmetric electrode system;

fig. 4 schematically presents a variant of the method for evaluating and controlling the susceptibility of porous media to technological processes assisted by prior plasma surface activation, in which the increase in the surface free energy of the porous media is achieved by direct microplasma treatment of the surface in a dielectric barrier discharge that burns in three-electrode (triode) plane-parallel asymmetric electrode system;

fig. 5 schematically presents a variant of the method for evaluating and managing the susceptibility of porous media to technological processes assisted by preliminary plasma surface activation, in which the increase in the free surface energy of the porous media is achieved by remote microplasma treatment of the surface with the products containing chemically active particles ( HAC) produced by a dielectric barrier discharge burning in a two-electrode plane-parallel asymmetric electrode system;

fig. 6 schematically presents a variant of the method for evaluating and managing the susceptibility of porous media to technological processes assisted by prior plasma surface activation, in which the increase in the surface free energy of the porous media is achieved by remote microplasma surface treatment with the products containing HAC produced by dielectric barrier discharge burning in a three-electrode planar-parallel asymmetric electrode system;

fig. 7 schematically represents the wetting pattern of an "ideal" surface after placing a stationary drop of liquid on the horizontal smooth, non-porous, solid surface, with both the solid and the liquid in contact with the gas/vapor; the system is not in equilibrium and the liquid wets and spills outward on the surface until the contact angle Θ assumes a value equal to zero: Θ = 0°: cos θ= 1, (Good, 1993);

fig. 8 presents a model of wetting of a "real" surface after placing a stationary drop of liquid on a horizontal rough, porous, inhomogeneous and hygroscopic surface, where two different phenomena are observed that directly affect the behavior of the stationary drop on the surface: i - spilling or spread of the liquid on the solid surface, as a result of wetting; And absorption or penetration (drainage) of the liquid into the porous medium, as a result of capillary absorption (Berg, 1993);

fig. 9 presents the variation of the interfacial energy osl at the "solid-liquid" interface, depending on the equilibrium contact angle θ', the so-called a "boundary line" that separates efficient from ineffective plasma-assisted processes, or compliant (os - yr > 0) from non-compliant (os - yL < 0) porous materials; the difference D = os - yL, which is equal to the interfacial energy osl at the "solid-liquid" interface, at a contact angle equal to zero (Θ = 0°: cos Θ = 1); the free surface energy os, which is exactly equal to the interfacial energy osl, at a contact angle equal to 90°, (Θ = 90°: cos Θ = 0);

fig. 10 presents the technological characteristics of a barrier dielectric discharge "surface density of the active power - size of the air (working) gap" depending on the voltage - formulation of technologically effective active power air gaps (at voltages up to 30 kV rms);

fig. 11 presents the variation of the interfacial energy (MFE) at the solid-liquid interface, depending on the contact angle, when evaluating the acquired susceptibility to impregnation after plasma surface activation with distilled water (DW) - the difference between the acquired after plasma activation free surface energy of the four types of heartwood - European white pine (Pinus Sylveslris), tzalam (Lysiloma Bahamensis), Mexican white cedar (Cupressus Lusitanica) and mahogany mahogany (Swietenia Macrophylla) and the surface tension of the liquid, i.e. the value of the interfacial energy at a contact angle equal to zero is a negative value, which indicates insufficient acquired susceptibility to impregnation;

fig. 12 presents the variation of the interfacial energy at the "solid-body-liquid" limit, depending on the contact angle, when testing heartwood from European white pine (Pinus Silvestris, Bulgaria) with distilled water (DW) and with impregnating

solution containing phosphorous flame retardant (FR) as a function of dielectric barrier discharge voltage (DBR) - illustrates the inability of the distilled water test to reveal effective modes of plasma activation, - the impregnating phosphorous flame retardant test indicates the modes at 15 and 17 kV rms as technologically effective, and the activated porous material as susceptible to impregnation;

fig. 13 presents the variation of the interfacial energy at the "solid-body-liquid" limit, depending on the contact angle, when testing heartwood of the four investigated species, fig. 11, is the initial (baseline) impregnation solution containing phosphorous flame retardant (FR), before (control sample) and 2 hours after direct plasma activation is DBR: none of the control samples succumbs to impregnation, while three types of wood acquire the required susceptibility after plasma activation - the European white pine, ttsalama, and the Mexican white cedar, the activation of mahogany caoba cannot provide the necessary susceptibility to impregnation with an open time of 2 hours for the realization of the process outside the technological line;

fig. 14 shows the change in interfacial energy at the solid-liquid boundary, depending on the contact angle, when testing heartwood of European white pine, tzalam, Mexican white cedar and mahogany mahogany with the modified anionic micellar (aqueous) surfactant impregnating solution containing phosphorous flame retardant (FR), before (control sample) and 2 hours after direct plasma activation with DBR: all samples were susceptible to impregnation at an open time of 2 hours, with higher susceptibility to impregnation after plasma-chemical activation ;

fig. 15 presents the variation of the interfacial energy at the solid-liquid boundary, depending on the contact angle, when testing heartwood of European white pine, tzalam, Mexican white cedar and mahogany mahogany with the original (base) and the modified anionic micellar surfactant impregnating solution , containing a phosphorous flame retardant (FR), 24 hours after direct plasma activation was DBM: all samples were subjected to plasma-assisted impregnation with the anionic surfactant-modified FR-A5 solution, at an open time of 24 hours, while three of the investigated wood samples are not amenable to plasma-assisted impregnation with the original impregnating solution FR, with the same open time of 24 hours;

S · * * · * · Q ·····»· * » ··· ···* « * ^Ф · ··· · · «· »··· fig. 16 presents the variation of the interfacial energy at the solid-liquid boundary, depending on the contact angle, when testing heartwood of European white pine with the original FR impregnating solution containing a phosphorous flame retardant and two types of surfactant-modified impregnating solution - one , FR-A5, with an anionic micellar-forming surfactant, and the second, FR-A5-S, with an anionic micellar-forming and nonionic trisiloxane surfactant, 2 and 24 hours after direct plasma activation with DBR\ plasma-assisted impregnation with the surfactant-modified impregnation solutions provided significantly improved susceptibility to impregnation;

fig. 17 presents the variation of interfacial energy at the solid-liquid boundary, depending on the contact angle, when testing heartwood of Mexican white cedar with the original FR impregnating solution containing a phosphorous flame retardant and two types of surfactant-modified impregnating solution - one , FR-A5, with an anionic micelle-forming surfactant, and the second, FR-A5-S, with an anionic micelle-forming and nonionic trisiloxane surfactant, 2 and 24 hours after direct plasma activation with DBR·. plasma-assisted impregnation with the surfactant-modified impregnating solutions provides significantly improved impregnation susceptibility;

fig. 18 presents the variation of the interfacial energy at the solid-liquid boundary, depending on the contact angle, when testing heartwood of Mexican white cedar with the starting impregnation solution FR containing a phosphorous flame retardant, 2 hours after direct plasma activation with DBR. with an air gap size of 12 mm;

fig. 19 shows the change in interfacial energy at the solid-liquid interface, as a function of contact angle, when testing Mexican white cedar heartwood with an anionic micellar surfactant-modified FR-A5 impregnating solution containing a phosphorous flame retardant, 2 hours after direct plasma activation with DBR at an air gap size of 12 mm;

fig. 20 represents the multitude of elementary processes taking place in air in its transformation into plasma by the barrier electric discharge which burns at normal atmospheric pressure, temperature and humidity;

fig. 21 presents the main chemical changes and reorganization of the surface after plasma-chemical activation, related to the active oxidation of the wood surface and the appearance of characteristic functional groups - a classification of the oxygen-containing functional groups on the surface after plasma-chemical activation with dielectric barrier discharge is presented;

fig. 22 presents the three main situations in which a significant reduction in impregnation susceptibility assessment is observed at the expense of a reduction in free surface energy - first, when introducing remote plasma activation with discharge products containing HAC; secondly, when the plasma activation is taken out of the process line; third, in the remote plasma activation outside the technological line;

Fig. 23 presents a general view of thermally developed test samples of European white pine (Pinus Sylvestris), as well as the general view of the protective coatings during impregnation in the direction of the capillary structure (front coating) - capillary impregnation, and in the direction transverse to the capillary structure ( top and bottom coatings) surface or impregnation through the capillary wall;

fig. 24 presents a general view of the coating and the characteristic imperfections and defects produced by plasma-assisted impregnation, transverse to the direction of the capillary structure or through the capillary wall.

Examples of implementation of the invention

According to the one presented in fig. 1, block process diagram, the implementation of the plasma-assisted surface impregnation process, outside the process line, requires not only the occurrence of the necessary for synchronizing two processes 1 (and/or 2) and 5 open time, but determines, by necessity, as a result of aging, the reduction of the acquired as a result of plasma activation 1 (and/or 2) free surface energy os,3 < asp, which can worsen the difference D = as,3 - var. Evaluating the susceptibility of the porous medium to impregnation with the starting solution FR, after aging 3, can give a negative evaluation: D = as.3 -ul< 0, i.e. integrally, the process should be ineffective, and the porous medium not amenable to impregnation.

In the event that the open time cannot be reduced, for technological reasons, the impregnating solution must be modified with a surfactant and/or heated to the permissible temperature so that its surface tension decreases ур < ул, i.e. to add the technological process 4 so that the evaluation of the permeability of the porous medium becomes positive: D = as,3 - y> 0.

The control of the technological process is carried out according to two degrees of freedom, the first one increases the free surface energy, and the second one - decreases the surface tension of the solution, so that as a result of these changes, the maximum possible positive assessment of the permeability of the porous medium at the set open time - D = as,3 - γκι» 0.

According to the one presented in Fig. 2, block technological scheme, the implementation of the plasma-assisted surface impregnation process, inside the technological line, does not require additional synchronization of two processes 1 (and/or 2) and 5 and additional open time other than zero, - aging of the activated surface is not allowed, therefore, the acquired as a result of plasma activation 1 (and/or 2) free surface energy, as.2 > as.i, most often determines a positive assessment of the susceptibility of the porous medium: D = as,2 - уь> 0. It is not necessary for the impregnating solution to be modified with a surfactant and/or heated so that its surface tension decreases in order to reach a positive assessment of susceptibility D. In this case, the control of the technological process is carried out by a single degree of freedom - the increase of the surface energy of the porous medium, so that as a result of this change, the maximum possible positive assessment of the medium's susceptibility is reached - D = as,2 - yr > 0.

According to the presented in Fig. 3, the control of the susceptibility D of the porous medium to surface impregnation is realized by increasing the free surface energy under direct microplasma activation in a dielectric barrier discharge that burns in a two-electrode (diode) planar-parallel (coplanar) asymmetric electrode system, such as the treated article 2 or more precisely, its two surfaces 2-1 and 2-2 pass once or repeatedly through the discharge gap that is formed between the dielectric barrier 3 located immediately next to the high-voltage planar electrode 1 and the grounded planar counterelectrode 4, after the source of high alternating voltage 6 applied voltage to the plane-parallel two-electrode system formed by the high-voltage electrode 1 and the grounded counter-electrode 4.

According to the presented in Fig. 4, the control of the susceptibility D of the porous medium to surface impregnation is carried out by increasing the free surface energy under direct microplasma activation in a dielectric barrier discharge that burns in a three-electrode (triode) plane-parallel electrode system, such as the treated article 2 or more precisely its two surfaces 2-1 and 2-2 pass once or repeatedly through the discharge gap, which is formed between the additional planar grid electrode 5, located immediately on the surface of the dielectric barrier 3, and the grounded planar counter electrode 4, after the source of high alternating voltage 6 applied a voltage to the plane-parallel two-electrode system formed by the high-voltage plane electrode 1, located tightly on the other side of the dielectric barrier 3 and the grounded counter electrode 4; the additional mesh electrode 5 is galvanically connected to the high-voltage electrode 1 through the reactive component (capacitor) 7.

As shown in Fig. 5, control of the susceptibility D of the porous medium to surface impregnation is achieved by increasing the surface free energy in unilateral remote microplasma activation with HAC-containing products produced in a dielectric barrier discharge burning in a two-electrode planar-parallel asymmetric electrode system, as treated article 2 or more precisely one of its surfaces 2-1 is activated once or repeatedly with an air stream containing HAC that has previously passed through the discharge gap that is formed between the grounded mesh planar counter electrode 4 and the dielectric barrier 3 located immediately to the high-voltage planar electrode 1, and leaves the discharge gap through the mesh electrode 4 after the high alternating voltage source 5 has applied voltage to the two-electrode system formed by the high-voltage electrode 1 and the ground electrode 4; after interacting with the surface 2-1, the active air flow leaves the closed active volume 6 through the semi-permeable barrier - the brushes 7 and enters the surrounding air; the one-sided processing of the surface 2-1 of the article 2 is carried out "step by step", by relative movement of the active volume 6 on the surface 2-1 of the article 2, carried out by sliding on the brushes 7, until the complete activation of the entire surface 2-1 .

According to the presented in Fig. 6, control of the susceptibility D of the porous medium to surface impregnation is achieved by increasing the surface free energy in unilateral remote microplasma activation with HAC-containing products produced in a dielectric barrier discharge burning in a three-electrode planar-parallel asymmetric electrode system, as treated article 2 or more precisely one of its surfaces 2-1 is activated once or repeatedly with an air stream containing HAC that has previously passed through the discharge gap that is formed between the grounded mesh insulated counter electrode 4 and the additional electrode 8 located on the dielectric barrier 3, located in turn immediately next to the high-voltage planar electrode 1, and leaves the discharge gap through the mesh electrode 4, after the source of high alternating voltage 5 has applied voltage to the high-voltage electrode 1 and galvanically connected to it through the capacitor C additional electrode 8 and h ground electrode 4; after interacting with the surface 2-1, the air flow containing HAC leaves the closed active volume 6 through the semi-permeable barrier - the brushes 7, and enters the surrounding air; the one-sided processing of the surface 2-1 of the article 2 is carried out continuously "step by step", by the relative movement of the active volume 6 on the surface 2-1 of the article 2, carried out by sliding on the brushes 7, until the complete activation of the entire surface 2- 1.

According to fig. 7, the presented model of wetting of an "ideal" surface involves the placement of a stationary drop of liquid on a horizontal smooth, non-porous, solid surface, where the solid and liquid are in contact with ambient gases/vapours, in addition to each other. The system is not in equilibrium and the liquid wets by spilling over the surface, outside the base of the drop, until the contact angle Θ assumes its equilibrium value. The contact angle change is solely due to surface wetting, and the equilibrium wetting contact angle satisfies Young's law, Eq. 1.

According to fig. 8, the presented model of wetting of a "real" surface also includes the placement of a stationary drop of liquid on a horizontal rough, porous, inhomogeneous and hygroscopic surface, where two different phenomena are observed, however, which determine the behavior of the stationary drop on the surface: i - the spilling of the liquid on the solid surface, outside the base of the drop, as a result of wetting; and - the absorption of the liquid into the porous medium, as a result of capillary penetration into the porous medium. The change in the contact angle is already due, in addition to the wetting of the surface, to the absorption of the liquid in the porous medium. The equilibrium contact angle also apparently satisfies Young's law, Eq. 1. The free surface energy determined by measuring the contact angle also reflects the phenomenon as a whole and should be accepted as an apparent (effective) physical quantity.

According to fig. 9, the variation of the interfacial energy osl at the "solid-liquid" interface, depending on the variation of the equilibrium contact angle Θ in the range [0°; 90°], allows the following basic concepts to be formulated:

1. The "boundary line", with difference D = as - уь = 0 or as = ус, with equation:

OSb = as - yiCOS Θ = уь (1 - cos Θ), ' ' which separates effective from ineffective plasma-assisted processes or susceptible (D = as - ую > 0) from unsusceptible (D = as - юю < 0) impregnation pores environments;

2. The estimate of the susceptibility D or the difference between the free surface energy as and the surface tension of the liquid }d, D ~ as - ую, which is exactly equal to the interfacial energy osl at the "solid-liquid" interface, at a contact angle equal to zero (Θ = 0°: cos 0=1), i.e. if using Eq. 1, it

D = as - уь = asL (θ = 0°).

The equation that represents the difference D between the free surface energy as and the surface tension of the liquid uy, when satisfying Eq. 1, can be represented as follows:

D = as-yb = osl + уь (cos θ - 1).

3. The free surface energy as is exactly equal to the interfacial energy az, at a contact angle equal to 90°, (0 = 90°: cos 0 = 0) and this follows directly from Eq. 1:

osl (0 = 90°) = as. ⁽⁵⁾

4. Susceptible to impregnation, with a solution having a surface tension uy, is any porous surface whose curve of dependence of the interfacial energy osl on the equilibrium contact angle 0, in the variation interval 0 is [0°; 90°], lies above the boundary line of osl or as > уь, i.e. D = as- уь > 0. The difference D serves to evaluate the degree of susceptibility of the surface to impregnation with a particular solution, and the greater this difference, the higher the susceptibility of the porous medium to impregnation.

According to fig. 10, the presented technological characteristics of a dielectric barrier dielectric discharge "surface density of active power r _and size of the air (working) gap d", depending on the voltage U, allow to formulate technologically effective active power air gaps (at voltages up to 30 kV rms) - these are the air gaps 6 and 12 mm, which correspond to a streamer mode of burning of the dielectric barrier discharge in air at atmospheric pressure and ambient temperature.

According to fig. 11, the evaluation of the acquired impregnation susceptibility to distilled water (DW) of four types of wood of different origins, after plasma surface activation in technologically effective modes and aging for 2 hours, is presented. This is done through the dependence of the interfacial energy osl, at the "solid-liquid" boundary, depending on the variation of the equilibrium contact angle Θ in the interval [0°; 90°]. None of the wood samples of European white pine, tzalam, Mexican white cedar and mahogany mahogany acquired a positive assessment of susceptibility to impregnation with distilled water after the plasma activation and an open time of 2 hours - D = os - въ < 0. Thus, none of the presented dependences is located above the abscissa - the acquired susceptibility to impregnation, although higher than that of the control samples K, remains low, given the results sought. The surface free energy is quantified by measuring the equilibrium contact angle, according to the Wu model or theory, which is valid for highly polar and high energy surfaces. The open time of 2 hours completely compromises the results of the pre-plasma activation. The plasma-assisted surface impregnation process is not applicable to distilled water impregnation.

According to fig. 12, the evaluation of the acquired susceptibility to impregnation is presented is distilled water (DW) and a phosphorus impregnating solution with about 30 wt. % dry matter (about 11 wt. % phosphorus content) of control and experimental specimens of European Scots pine (Pinus Sylvestris), after plasma surface activation in different regimes of DBM, determined by the voltage -11, 13, 15 and 17 kV rms , and aging for 2 hours, i.e. open time 2 hours. This is done again by the dependence of the interfacial energy osl at the "solid-liquid" boundary on the variation of the equilibrium contact angle Θ in the interval [0°; 90°]. The test with distilled water (-DW), as a control liquid with a surface tension ух = 72 mN/m, did not form a positive assessment of the susceptibility of any of the control and experimental specimens to surface impregnation - none of the presented dependences were completely located above the abscissa, and the difference D = os - y < 0.

At the same time, the test is an impregnating aqueous solution of the phosphoric flame retardant (-FR), at a surface tension ух = 46.4 mN/m, reveals the effectiveness of plasma activation modes above 15 kV rms. This figure illustrates a basic principle in the testing of the activated surface, especially after 2 hours of active aging and reorganization of the surface: the determination of the susceptibility to impregnation and more precisely of the free surface energy must be carried out necessarily with the used impregnating solution or with a test solution , having a surface tension as close as possible to its own.

Distilled water cannot act as a test solution in this test because the two surface tensions differ significantly: 72 mN/m > 46.4 mN/m. Evaluation of impregnation susceptibility using the D rating indicates that the plasma-assisted impregnation process can only be effective at voltages above 15 kV rms. The control of the plasma-assisted surface impregnation process with the phosphoric flame retardant can be successfully realized by selecting the combustion mode of the DBM through the voltage.

According to fig. 13, the assessment of the acquired susceptibility to impregnation with an aqueous solution of phosphoric flame retardant - with about 30 wt. % dry matter (about 11 wt. % phosphorus content), of control and experimental specimens of European white pine (Pinus Sylvestris, Bulgaria), tzapam (Lysiloma Bahamensis, Mexico), Mexican white cedar (Cupressus Lusitanica, Mexico) and mahogany kaoba (Swietenia Macrophylla, Mexico) after plasma surface activation in effective voltage regimes defined as follows - for European white pine - 15 kV rms, for other tree species - 18 kV rms, and open time after activation - 2 hours.

This is done through the dependence of the interphase energy I at the "solid body-liquid" boundary on the change in the equilibrium contact angle Θ in the interval [0°; 90°]. This figure shows that none of the four control specimens succumbed to surface impregnation with the FR base phosphor solution. There is a need for plasma activation of the surface of the porous medium.

The preliminary plasma-chemical activation, for three of the four types of wood, turns out to be the sought-after solution - the susceptibility of the investigated sample bodies to surface impregnation is evaluated as positive: the dependence of the interfacial energy 6sl on the equilibrium contact angle Θ takes only positive values 6sl > 0 in the interval 0° < Θ < 90° or the difference D = os-yL > 0. This evaluation shows that only mahogany does not lend itself to plasma-assisted impregnation at the stated need for an open time of 2 hours. Another solution should be sought, for example, by further modifying the impregnating solution by reducing the surface tension -y< 46.4 mN/m.

According to fig. 14, the evaluation of the acquired susceptibility to impregnation by the modification of the base aqueous FR impregnating solution with an anionic micellar-forming surfactant introduced in 5 vol. %, of the control and experimental specimens of European Scots pine, tzalam, Mexican white cedar and mahogany, after plasma surface activation at the known effective voltage regimes, and an open time of 2 hours after activation. This is done through the dependence of the interfacial energy osl at the "solid-liquid" boundary on the variation of the equilibrium contact angle Θ in the interval [0°; 90°].

This figure shows that all four control specimens were effectively surface impregnated with the modified FR-A5 phosphor solution. It can be concluded that the use of the modified impregnating solution changes to the required degree the impregnation susceptibility of the porous media, i.e. the difference D acquires positive values, D > 0, as follows, mN/w: for mahogany - + 5.5; white pine - + 7.5; cedar - + 16.2 and tzalama + 24.1.

The preliminary plasma activation, however, increases to an even greater extent the impregnation susceptibility of the test bodies, and the difference D increases significantly, mN/m: for mahogany - by 12.8; tsalama - with 16.7; cedar - with 17.6 and white pine - with 22.8. At the same time, the final estimates of susceptibility, after plasma activation, are arranged in the same way, mN/w: for mahogany - 18.2; white pine - 31.8; cedar - 33.8 and tzalama - 40.8.

It can be recommended to control the susceptibility to surface impregnation simultaneously along the two degrees of freedom - the preliminary plasma-chemical surface activation and the modification of the impregnating solution, i.e. increasing the difference D by increasing the surface free energy and decreasing the surface tension of the impregnating solution, whereby all four wood porous media surely receive a positive evaluation for their susceptibility to impregnation.

According to fig. 15, the evaluation of the acquired susceptibility to impregnation with the FR base aqueous solution of the phosphoric flame retardant and the modified solution (FR-A5) - with an anionic micelle-forming surfactant introduced in 5 vol. %, of the experimental specimens of European white pine (Pinus Sylvestris), tzalam (Lysiloma Bahamensis), Mexican white cedar (Cupressus Lusitanica) and mahogany (Swietenia Macrophylla), after plasma surface activation in the known effective regimes of voltage and open time after activation - one day or 24 hours. This is done through the dependence of the interfacial energy osl at the "solid-body-liquid" limit on the change in the equilibrium contact angle Θ in the interval [0°; 90°].

This figure shows that all four control specimens were effectively subjected to plasma-assisted surface impregnation, while providing the required open time of 24 hours, with the modified FR-A5 phosphor solution.

Evaluation of the susceptibility of these same specimens to impregnation with the FR base impregnating solution showed that only the European white pine specimens could be effectively impregnated under these conditions. Increasing the open time from 2 to 24 hours requires a universal solution - to increase the susceptibility of the porous test bodies to impregnation, using both degrees of freedom in its control - the increase of the free surface energy after 24 hours of aging by preliminary plasma- chemical surface activation and the reduction of the surface tension of the base impregnating solution by modifying it with an anionic micelle-forming surfactant - from 46.6 to 22.4 mN/m.

It can be concluded that the use of the modified impregnating solution FR-A5 changes the impregnation susceptibility of porous media to the required extent, i.e. the difference D > 0 acquires values as follows, mN/m: for mahogany - 12.4; tsalama - 15.1; cedar - 16.4 and white pine - 26.1. The evaluation of the susceptibility of white pine to impregnation with the base solution, after plasma-chemical surface activation is positive, but too close to the limit value, mN/m: D = 2.1 >0. For this reason, it can be confidently stated that this susceptibility is too low to create a sustainable technology, 2.1 « 26.1, therefore the general conclusion remains valid for all types of wood.

According to fig. 16, a summary evaluation of the acquired susceptibility to impregnation with three impregnating solutions is presented, with decreasing surface tension the base aqueous solution FR of the phosphorous flame retardant - by about 30 wt. % dry matter (about 11 wt. % phosphorus content) - 46.4 mN/m; the modified FR-A5 solution - with an anionic micelle-forming surfactant, in 5 vol. %, - 22.4 mN/m and the modified solution (FR-A5-S) - is an anionic micelle-forming surfactant, in 5 vol. %, and nonionic trisiloxane surfactant, in 0.1 vol. %, - 18.5 mN/m, on control specimens K from European white pine (Pinus Sylvestris), and on experimental specimens after plasma surface activation in the known effective voltage regime - 15 kV rms, and different open time after activation - 2 hours (LF2) and one day or 24 hours (LF24).

This is done again by the dependence of the interfacial energy osl at the solid-liquid interface on the variation of the equilibrium contact angle Θ in the interval [0°; 90°]. This figure shows that the universal solution that provides open time up to the hour of plasma-assisted post-treatment is the modification of impregnating solutions with surfactants. The FR base aqueous solution (46.4 mN/m) does not allow to provide open time up to 24 hours, even after plasma assisted process. The modified solution FR-A5-S provides the necessary open time of one day with very good susceptibility of all samples, mN/m: K- + 11.4; LF2 - + 46.5 and LF24 - + 25.6. The modified solution FR-A5 also, but to a lesser extent, provides the necessary open time of one day with good compliance of all samples, mN/m: K - + 7.5; LF2 - + 42.6 and LF24 + 21.7. The FR base solution, however, provides the required open time of one day on only one sample: LF2 + 19.0 mN/m.

The general control approach, through the two degrees of freedom - the increase of the free surface energy through plasma-chemical surface activation and the decrease of the surface tension of the impregnating solution, allows to ensure the necessary susceptibility of the porous medium to surface impregnation even at large open times (24 o'clock). Moreover, shown in the figure, it can be argued that the so-called critical open time at which the difference D becomes equal to that of the control, i.e. the effect of plasma activation is deleted, is significantly greater than 24 hours: for the modified solution FR-A5-S - it is + 25.6 > + 11.4 mN/m, and for the modified solution FR-A5 - it is + 21.7 > + 7.5 mN/m.

According to fig. 17, heartwood of Mexican white cedar (Cupressus Lusitanica) has a critical open time of less than 24 hours, i.e. the effect of plasma activation wears off in less than 24 hours. A summary of the evaluation of plasma-activated susceptibility after 2 and 24 hours of air aging under normal conditions is presented. Susceptibility to impregnation was evaluated against the three impregnating solutions, with a decreasing surface tension - the FR base aqueous solution of the phosphorous flame retardant - by about 30 wt. % dry matter (about 11 wt. % phosphorus content) - 46.4 mN/m; the modified FR-A5 solution - with an anionic micelle-forming surfactant, in 5 vol. %, - 22.4 mN/m and the modified solution FR-A5-S - with an anionic micelle-forming surfactant, in 5 vol. %, and nonionic trisiloxane surfactant, in 0.1 vol. %, - 18.5 mN/m. Susceptibility to impregnation was evaluated on control test specimens K and experimental test specimens, after plasma surface activation in the known effective mode voltage 18 kV rms, and different open time after activation - 2 hours (LF2) and one day or 24 hours (LF24) . This is done through the dependence of the interfacial energy osl at the solid-liquid interface on the change in the equilibrium contact angle Θ is

[0°; 90°]. Under these conditions, the allowable 'Open Time' should be less than 24 hours or, using an exponential model of the kinetics of the change in D\ upon impregnation with the FR-A5-S solution after plasma activation:

= 40.711 exp (-0.0384 T), then the critical open time is about 18.5 hours;

when impregnating with the FR-A5 solution after plasma activation:

D- 25.016 exp (-0.0210 T), then the critical open time is about 21 hours.

According to fig. 18, the approach used allows selection of an effective voltage-dependent plasma activation mode, with pre-activation occurring at increasing voltages 11, 13, 15, 17, 19, 21 kV rms, but at twice the discharge gap d = 12 mm, in the area B of the technological characteristic of the dielectric barrier discharge presented in fig. 10. Susceptibility to impregnation was evaluated against the FR base water solution of the phosphorous flame retardant - with a surface tension of 46.4 mN/m. A maximally high susceptibility to surface activation with the FR base solution was found in the range 19-^21 kV rms, with the interfacial voltage curves superimposed on each other. Voltages above 13 kV rms can be assumed to provide a positive susceptibility rating, D > 0, at an open time of 2 hours.

According to fig. 19, the technological approach used allows selection of an effective voltage-based plasma activation mode, with pre-activation also occurring at increasing voltages of 11, 13, 15, 17, 19 and 21 kV rms, but at double the discharge gap d = 12 mm, in the area B of the technological characteristic of the dielectric barrier discharge, presented in fig. 10. Susceptibility to impregnation was evaluated against the modified aqueous solution FRA5 - with anionic micelle-forming surfactant - 5 vol. %, with a greatly reduced surface tension - from 46.4 to 22.4 mN/m. Maximum surface activation susceptibility with the FR base solution is again found in the range 19^-21 kV rms - 38.43 mN/m, with the interfacial tension curves superimposed on each other. It can be assumed that voltages of 11 kV rms upwards provide a positive susceptibility rating - D > 0, with an open time of 2 hours. The control sample, however, also has a positive assessment of susceptibility to impregnation, albeit the lowest: + 7.46 mN/m.

According to fig. 20, the result of the plasma activation is determined by the elementary processes that take place in the air during its transformation into a cold (non-equilibrium) technological plasma. When considering the results of direct plasma activation, the higher energy and electron concentration must be taken into account, as the light component continuously transfers energy from the electric field to the heavy plasma component. This determines its non-equilibrium nature and the large difference in the temperatures of the light and heavy components. The plasma activation is also affected by the presence of UV radiation, as a result of the significantly more intense processes of ionization and recombination. In remote plasma activation, the external electric field is absent, which significantly changes the participation of the electrons. Remote plasma activation is primarily based on the chemical activity of particles - atoms, excited atoms and molecules, ions and strong oxidants, such as ozone (and its decay products excited molecular oxygen and atomic oxygen) and nitrogen oxides. The so-called nitrogen mode of discharge combustion, in which the dissociation and ionization of nitrogen play an essential role in the elementary processes.

According to fig. 21, oxygen-containing functional groups appear or grow after the interaction of the porous surface with the plasma of the discharge and/or with the products carried out of the discharge, which determine the oxidative nature of the plasma-chemical surface activation. A classification (according to Kazayawoko, 1998) of the oxygen-containing functional groups into four classes is presented, according to the number of oxygen atoms connected to the carbon atom: class Cl (283.9 eV) - without a single oxygen atom connected to a carbon atom; a carbon atom bonded to a carbon or hydrogen atom (C-H; C-C); class C2 - with one oxygen atom (C-O; C-OH; C-OOH); class C3 - with two oxygen atoms (O-C-O) or with one carbonyl oxygen atom (C=O); class C4 - with one carbonyl oxygen atom and one carbonyl atom (OC=O).

According to fig. 22, there are three main implementations of plasma-chemical surface activation, in which a significant reduction in impregnation susceptibility assessment is observed at the expense of a significant reduction in free surface energy - first, when introducing remote plasma activation with discharge products containing HAC ; secondly, when the plasma activation is taken out of the process line, due to aging, i.e. chemical reorganization under the influence of ambient air; thirdly, in the combination of the remote plasma activation is the realization of the technological Mrotseb UgL The most advanced line. It is known that even with direct plasma activation, in the conditions of the technological flow line - the reduction of the difference D, respectively of the free surface energy is from 3 to 10 mJ/m ² . In the most unfavorable plasma activation - the one remote from the discharge and outside the process line, this reduction can reach over 20 mI/m ² and make the preliminary plasma activation meaningless. The presented values, which quantify the decrease in surface free energy, are the result of own research.

According to Fig.23, the produced protective coatings of phosphoric flame retardants can be thermally developed by heating at temperatures above 185 °C: European white pine (Pinus Sylvestris) test specimens are shown developed at temperatures of 190, 210, 230, 250 and 270 °C. It can be clearly seen that at temperatures above 270 °C the coating becomes more and more difficult to distinguish from the environment, as the charring (browning) of the wood itself begins. Thermally developed protective coatings are presented when impregnating in the direction of the capillary structure (front coating), i.e. capillary impregnation and across the capillary structure (top and bottom coatings) or surface impregnation, i.e. impregnation through the capillary wall. Both types of coatings are obtained on the same sample as a result of its impregnation. Critical to the protective action of the coating as a whole are surfaces with thinner (top and bottom coating) and poor quality coating containing many imperfections and defects.

According to fig. 24, increasing the thickness of the coating, in the areas of surface impregnation, where the coating is many times thinner, is essential for the protection of the specimen as a whole. It turns out that it is more important to obtain a uniform thickness, complete, uninterrupted and defect-free coating, rather than increasing the thickness, since it remains below 500 rsh. The figure shows the general appearance of the coating and its characteristic imperfections and defects obtained during impregnation, transverse to the direction of the capillary structure.

The method for evaluating and managing the susceptibility of porous media, for example, wood, cellulose and their products, to the plasma-assisted pre-surface activation process, and more specifically to plasma-assisted off-line surface impregnation to impart the property of difficult flammability, is illustrated by the following examples:

Example 1.

Samples of white - without plugs, European white pine (Finns Sylvestris, Bulgaria) are processed according to the invention, initially the surface of the samples is directly activated for 60 s in the air plasma of a dielectric barrier discharge at atmospheric pressure burning in air in a plane-parallel electrode asymmetric system with a dielectric barrier of alkaline glass (relative dielectric permittivity: e _d = 10), fig. 3, in mode A of microplasma activation - size of the discharge gap d = 6 mm, fig. 10, at voltages above 10 kV rms and industrial frequency (50 Hz).

Task·. To select a marginal effective mode of direct plasma activation of the test bodies by selecting the minimum burning voltage of the DBR, evaluating the acquired susceptibility to surface impregnation with a brush or roller, according to the invention, by the difference between the acquired free surface energy and the surface tension of the impregnating protective aqueous solution FR containing a phosphoric flame retardant, measured after aging the activated surface free in air for 2 hours, i.e. the plasma-assisted impregnation process is designed to be realized off the technological line with an open time of 2 hours.

The initial assessment for susceptibility to impregnation D with the specified solution FR is determined after measuring, according to the invention, according to known methods and devices (DSA100B and DSA30B) of the company "ΛζΐΑν": first, the free surface energy 6s of the initial control sample K by the Fowkes, Wu, EOS and Zisman theoretical models, by measuring the contact angle Θ of a stationary drop on a surface; second, the surface tension yi. of the solution by the Young-Laplace model, by the hanging drop method. The value of the free surface energy is as = 29.86 < 42.00 mJ/m ² , which means that the surface is low-energy, and the surface tension of the solution is уь = 46.40 mN/m. The assessment of susceptibility of the control sample to surface impregnation according to the invention is: D = 29.86 - 46.40 = - 16.54 mJ/m ² or D < 0: the control sample is not susceptible to impregnation with the solution specified for this, which requires the assistance of the impregnation process by preliminary plasma-chemical surface activation.

The technology of direct plasma surface activation is chosen, outside the technological line, with a required open time of 2 hours. The following modes of direct microplasma activation, U > 10 kV rms, are selected sequentially by voltage: 11; 13; 15 and 17 kV rms. The required minimum number of 3 test bodies for ··· · · · · · · each activation mode are processed, and Voefd values of the acquired free surface energy are determined according to the invention. After the test, the following series of free surface energy values for the respective plasma modes of direct activation after an open time of 2 hours is obtained, mJ/m ² : 41.16; 43.83; 54.20 and 62.23. According to the invention, the following four new evaluations of the susceptibility of the examined sample bodies to surface impregnation, mJ/m ² : - 4.84; - 2.17; + 8.20 and + 16.23.

The first mode of direct plasma activation, under the stated conditions, which provides the necessary minimum positive assessment of susceptibility, is determined by the difference D > 0, i.e. from the voltage U = 15 kV rms. All modes of direct microplasma activation at voltages above the minimum, U > 15 kV rms, satisfy acquired susceptibility to impregnation.

Example 2.

Samples of sapwood - without plugs, tropical mahogany - mahogany caoba (Swietenia Macrophylla, Mexico) were treated under the conditions of Example 1.

Task: To select an effective mode of direct plasma activation of the test bodies or/and appropriate modification of the impregnation solution with surfactant, evaluating the acquired susceptibility to surface impregnation with a brush or roller, according to the invention, by the difference between the acquired free surface energy and the surface voltage of the impregnating protective aqueous solution containing phosphoric flame retardant, measured after aging the activated surface free in air for 2 hours, i.e. the process of plasma-assisted impregnation is designed to be realized outside the technological line, with an open time of 2 hours.

The initial evaluation for susceptibility to impregnation D of the control body with the specified solution is determined after measuring, according to the invention, according to the known methods with devices (DSA100B and DSA30B) of the company "Xrwss": first, the free surface energy os of the initial control sample K according to the theoretical models of Fowkes, Wu, EOS and Zisman, by measuring the contact angle 0 of a stationary drop on the surface; second, the surface tension u of the solution according to the Young-Laplace model, according to the hanging drop method. The value of the free surface energy is os ~ 27.87 < 42.00 mJ/m ² , i.e. the surface is low-energy, and the surface tension of the solution is u = 46.40 mN/m. The assessment of susceptibility of the control sample to surface impregnation, according to the invention, is: D = 27.87 - 46.40 = 35

18.53 mJ/m ² , i.e. the evaluation is negative* 0. KNFol/sG *pillar does not lend itself to impregnation with the solution specified for it, which necessitates the assistance of the impregnation process by preliminary plasma-chemical surface activation.

The technology of direct plasma surface activation is chosen, outside the technological line, with a required open time of 2 hours. Different modes of direct microplasma activation, U > 10 kV rms, are selected sequentially by voltage, and their activation is carried out in the manner described in example 1.

According to the invention, the respective susceptibility ratings are determined, after which the mode of direct microplasma activation is selected which gives the highest susceptibility rating for impregnation with the FR base impregnation solution. The susceptibility estimate D is the highest in the microplasma mode of the DBR, determined by the voltage U= 18 kV rms, but unfortunately it is the lowest negative value: D = - 5.78 mJ/m ² < 0 at os = 40 .62 mJ/m ² . The best plasma-activated sample also does not lend itself to impregnation is the FR base solution, which necessitates the assistance of the impregnation process by reducing the surface tension u of the impregnation solution, according to the invention, with the help of surfactants.

An anionic aqueous micelle-forming surfactant - "Anticrystallin A" (Himatech, Bulgaria) was used, which was introduced in a concentration of 5 vol. % so as to ensure the conditions for micelle formation. The surface tension of the thus modified FR-A5 solution was determined in the described manner: y = 22.40 mN/m. The assessment of susceptibility to surface impregnation with the FR-A5 solution of the plasma-activated sample at an open time of 2 hours, according to the invention, is: D = 40.62 - 22.40 = + 18.22 mJ/m ² > 0. The direct plasma activation, using the modified solution FR-A5, already provides a positive assessment of the susceptibility of the porous material to surface impregnation at an open time of 2 hours.

It is mandatory to check the susceptibility to surface impregnation of the control specimen - without prior plasma activation, with the modified solution FR-A5\ D = 27.87 - 22.40 = + 5.47 > 0. The evaluation of susceptibility to surface impregnation shows , that the control specimen also lends itself well to impregnation with the modified FR-A5 solution. However, the comparison with plasma-assisted impregnation is not in its favor - after plasma activation, a significantly higher degree of susceptibility to impregnation is obtained: + 18.22 > + 5.47 mJ/m ² .

*

The grounds for selecting the plasma protection/damage barrier* of impregnation with the modified solution FR-A5, at an open time of 2 hours, are determined by the protective properties of the coating, which are determined by the amount of solution that can absorb the porous medium, so that the resulting diffuse coating to provide protection against flame burning. The control specimen has an impregnation rate of 0.139 1/t ² (dm ³ /m ² ) or 139 ml/m ² in relation to the base solution FR - this is the maximum amount of absorbed solution, which, however, does not effectively protect the porous medium. The modified solution has an increased rate of impregnation compared to the control - 258 ml/m ² , but it also does not effectively protect the porous medium. The plasma-activated sample has a significantly higher rate of impregnation is the modified solution 490 ml/m ² , which exceeds the minimum amount of 300 ml/m ² , ensuring the protection of the porous medium against flame burning: 300 < 490 ml/m ² .

Example 3.

Samples of white pine - without plugs, wood of European white pine (Finns Sylvestris, Bulgaria), are processed under the conditions, according to example 1.

Task: To verify the best mode of direct plasma activation of the test bodies of European white pine (Pinus Sylvestris) - at U = 15 kV rms, by evaluating the acquired susceptibility to surface impregnation is a brush or a roller is the base impregnation solution FR, with a significantly greater required open time of one day (24 hours), according to the invention, by the difference between the acquired free surface energy and the surface tension of the impregnating protective aqueous solution FR containing a phosphorous flame retardant. The process of plasma-assisted impregnation is designed to be realized outside the technological line, with the required open time of 24 hours, i.e. impregnation should be done after aging the plasma-activated porous surface for 24 hours.

Susceptibility of the activated wooden surface to impregnation is evaluated after determining the acquired free surface energy, after 24 hours of aging of the surface in air under normal conditions - pressure, temperature and humidity. The determined, according to the invention, free surface energy is os = 48.47 mJ/m ² , which determines the positive assessment of susceptibility to impregnation is the base solution FR: D = 48.47 - 46.40 = + 2.07 mJ/m ² > 0. Direct plasma activation, using the base impregnating solution FR, provides the necessary positive assessment of the susceptibility of the porous material SHT TwerknZbtne iShrijing with an open time of 24 hours.

The same assessment can be made with respect to the modified impregnating solution FR-A5, which has a greatly reduced surface tension - ул = 22.40 mN/m. Direct plasma activation, using the modified impregnating solution FR-A5, however, provides an even higher positive evaluation of the susceptibility of the porous material to surface impregnation, at an open time of 24 hours: D = 48.47 22.40 = + 26 .07 mJ/m ² > 0.

Example 4.

Specimens of sapwood - coreless, heartwood tropical tzalam (Lysiloma Bahamensis, Mexico) were treated under the conditions of Example 1.

Task: To choose an effective mode of direct plasma activation of the test bodies by selecting the burning mode of the DBR by voltage, evaluating the acquired susceptibility to surface impregnation with a brush or roller, according to the invention, by the difference between the acquired free surface energy and the surface voltage of the impregnating protective aqueous solution FR containing a phosphorous flame retardant, measured after aging the activated surface in free air for one day, i.e. the plasma-assisted impregnation process is designed to be realized outside the technological line, with an open time of 24 hours.

The impregnation susceptibility assessment D of the plasma-activated sample body with the base impregnation solution FR is determined after measuring, according to the invention, in the manner described in example 1: first, the free surface energy os of the plasma-activated sample; second, the surface tension u of the solution. The value of the free surface energy of the control sample after 24 hours of air aging under normal conditions is os = 37.54 mJ/m ² , and the surface tension of the solution is y = 46.40 mN/m. The assessment of susceptibility of the control sample to surface impregnation, according to the invention, is: D = 37.54 - 46.40 = 8.86 mJ/m ² or D < 0. The control sample is not susceptible to plasma-activated surface impregnation with the base FR solution, which necessitates the mandatory support of the impregnation process by modification of the basic impregnation solution.

An anionic micelle-forming surfactant was used, which was introduced in a concentration of 5 vol. % so as to provide conditions for micelle formation. The surface tension of the FR-A5 solution thus modified is determined in the manner described above: y = 22.40 38 e········ mN/m. The evaluation of the susceptibility of po*£r>?ibstnb'im1Gregny]5in5 with the FR-A5 solution of the plasma-activated sample at an open time of 24 hours, according to the invention, is: D = 37.54 - 22.40 = + 15.14 mJ/m ² > 0. Direct plasma activation, using the modified FR-A5 solution, already provides a positive assessment of susceptibility of the porous material to surface impregnation, with an open time of 24 hours.

Example 5.

Samples of sapwood - without plugs, heartwood of Mexican white cedar (Cypressus Lusitanica, Mexico) are treated, according to the invention, by first activating the surface of the samples directly, for a time of 60 s, in the air plasma of the DBR at atmospheric pressure, which burns in air, in a plane-parallel electrode asymmetric system with a dielectric barrier of alkaline glass (relative dielectric permittivity: e _d = 10), fig. 3, in mode B of microplasma activation size of the discharge gap d = 12 mm, fig. 10, at voltages above 10kV rms and industrial frequency (50 Hz).

Task: To choose a marginal effective mode of direct plasma activation of the test bodies, by choosing the minimum burning voltage of the DBR, evaluating the acquired susceptibility to surface impregnation with a brush or roller, according to the invention, by the difference between the acquired free surface energy and the surface tension of the impregnating protective aqueous solution FR containing a phosphorous flame retardant, measured after aging the activated surface in free air for 2 hours, i.e. the plasma-assisted impregnation process is designed to be realized "off the line" with an open time of 2 hours.

The initial assessment for susceptibility to impregnation D with the specified solution is determined after measuring, according to the invention, according to the known methods described in example 1, the free surface energy as of the control sample after 2 hours of aging in air under normal conditions and the surface tension у of the FR solution. The value of the free surface energy is as = 29.86 mJ/m ² , and the surface tension of the solution is y = 46.40 mN/m. The assessment of susceptibility of the control sample to surface impregnation, according to the invention, is: D = 29.86 - 46.40 = 16.54 mJ/m ² or D < 0. The control sample does not lend itself to impregnation with the solution specified for this, which necessitates supporting the impregnation process by preliminary plasma-chemical surface activation.

The technology of direct miroplyzmen£G is selected for activation in mode B, outside the technological line, with a required open time of 2 hours. The following modes of direct microplasma activation, U> 10 kV rms, are selected sequentially by voltage: 11; 13; 15, 17, 19 and 21 kV rms. After the test, the following series of free surface energy values is obtained, for the corresponding plasma modes of direct activation, after an open time of 2 hours, mJ/m ² : 45.40; 47.67; 57.07; 57.63; 60, 21 and 60.83. According to the invention, the following four new evaluations of the susceptibility of the examined test bodies to surface impregnation are formed: - 1.00; + 1.27; + 10.67; + 11.23; + 13.81 and + 14.43 mJ/m ² .

The first mode of direct plasma activation, under the stated conditions, which provides the necessary minimum positive assessment of susceptibility, is determined by the difference D > 0, i.e. from the voltage U = 13 kV rms. However, the impregnation susceptibility rating value is too low, which carries a certain risk, therefore it can be assumed that the minimum positive rating should be determined at a voltage of 15 kV rms. All modes of direct microplasma activation at voltages above the minimum, U > 15 kV rms, satisfy acquired susceptibility to impregnation.

There is, however, an upper voltage limit - at voltages 19 and 21 kV rms, the differences in the acquired free surface energy become too small, therefore an interval of effective modes B of direct plasma activation can be defined by voltage U is [15; 19] kV rms.

Example 6.

Samples of white - without plugs, core pine wood (cham) from European Scots pine (Pinus Sylvestris, Bulgaria) are processed according to the invention, initially the surface of the samples is activated remotely, for 60 s, in the air plasma of a dielectric a barrier discharge at atmospheric pressure burning in a semi-open planar-parallel electrode asymmetric system with a dielectric barrier of alkaline glass (relative dielectric permittivity: e _d = 10), fig. 5, in mode A of remote microplasma activation - size of the discharge gap d = 6 mm, fig. 10, at a voltage of 21 kV rms and an industrial frequency (50 Hz).

Task: To verify the applicability of the chosen mode of remote plasma activation of the test bodies by evaluating the acquired susceptibility to surface impregnation with a brush or roller, according to the invention, by the difference between the acquired free surface energy and the surface tension of the 40 impregnating protective aqueous solution FR , with flame retardant retention, measured after aging the activated surface in free air for 2 hours, i.e. the plasma-assisted impregnation process is designed to be realized off the technological line with an open time of 2 hours.

An assessment of susceptibility to impregnation D with the base impregnation solution FR is determined after measuring, according to the invention, according to the methods described in example 1, the free surface energy as of the activated sample and the surface tension y of the FR solution. The value of the free surface energy of the plasma-activated test body, after 2 hours of open time, is as = 49.67 mJ/m ² , and the surface tension of the solution is y = 46.40 mN/m. The assessment of susceptibility of the plasma-activated sample to surface impregnation, according to the invention, is: D = 49.67 - 46.40 = + 3.27 mJ/m ² or D > 0: the plasma-activated sample body is susceptible to impregnation with the base solution FR.

An impregnation susceptibility score D was determined with the anionic micelle-forming surfactant-modified impregnating solution FR-A5, which has a greatly reduced surface tension - y = 22.40 mN/m. The assessment of susceptibility of the same plasma-activated sample to surface impregnation, according to the invention, is: D = 49.67 - 22.40 = + 27.27 mJ/m ² or D > 0. The plasma-activated sample body is susceptible to impregnation in many a greater degree with the modified impregnating solution FRA5: 27.27 » 3.27.

The use of non-polar trisiloxane surfactant - ¥17113 (Moment ive Performance Materials GmbH & Co., Germany), c critical concentration 0.1 vol. %, additionally added to the modified solution FR-A5, allows the surface tension of the impregnating solution FR-A5-S to be reduced to y = 18.50 mN/m. The assessment of susceptibility of the same plasma-activated sample to surface impregnation with the new solution FR-A5-S, according to the invention, is: D = 49.67 - 18.50 = + 31.17 mJ/m ² or D > 0. The plasma-activated test body is more susceptible to impregnation with the modified FR-A5-S impregnation solution: + 31.17 > + 27.27 » + 3.27.

LITERATURE

1. Theory note 4: “Surface free energy - theory and calculations'”, Attension Biolin Scientific, Finland, www.attension.com (2016).

2. Why test inks cannot tell the full truth abmft surface free ert^y. Application report No 272, Kriiss GmbH, Hamburg, Germany, www.kruss.de (2014).

3. Dyne testing - all about dynes. Webconvert Ltd., Toronto, Ontario, Canada, www.webconvert-ltd. Com (2016).

4. Dyne pens and how to measure surface tension. Vetaphone A/S, Denmark. www.vetaphone.com (2016).

METHOD FOR ASSESSING AND CONTROLLING THE SUSCEPTIBILITY OF POROUS MEDIA TO PLASMA-ASSISTED BY ACTIVATION TECHNOLOGICAL PROCESSES

Claims (10)

1. A method for evaluating and managing the susceptibility of porous media to plasma-assisted through prior surface activation technological processes functionalization or oxidation, and more specifically to plasma-assisted surface impregnation outside the process line, i.e. after the manifested aging of the activated surface in air under normal conditions - atmospheric pressure, ambient temperature and humidity, including an increase in the surface free energy by direct treatment of the surface with non-equilibrium (cold) dielectric barrier discharge plasma in air at atmospheric pressure and room temperature and /or by remote treatment of the surface with discharge products - gases and vapors containing chemically active particles, and reducing the surface tension of the impregnating solution with the help of surfactants (surfactants), characterized by the fact that the impregnation susceptibility of the impregnation surface is evaluated by the difference between the free surface energy determined at the end of the open process time, characterizing the degree of aging of the activated surface, and the surface tension determined after the addition of the surfactant, and the control of susceptibility is carried out by increasing its the sting surface energy upon preliminary plasma activation and reduction of the surface tension of the impregnating solution by using anionic surfactants alone or in combination with neutral and/or amphoteric surfactants and/or increasing its temperature so that this difference is a positive value, where the larger it is, the more susceptible the porous medium becomes to the plasma-assisted impregnation process. 2. A method for evaluating and managing the susceptibility of porous media to plasma-assisted by prior surface activation technological processes and more specifically to plasma-assisted surface impregnation, off the process line, according to claim 1, characterized in that the surface free energy is determined by measuring the equilibrium contact angle by the stationary drop method with two or three liquids using the known computational models. 3. A method for evaluating and managing the susceptibility of porous media to plasma-assisted pre-surface activation technological processes and in particular to plasma-assisted surface impregnation outside the technological line, according to claim 1, characterized in that the surface tension of the liquid is determined by measuring the equilibrium wetting contact angle using the hanging drop method. 4. A method for evaluating and managing the susceptibility of porous media to plasma-assisted by prior surface activation technological processes and more specifically to plasma-assisted surface impregnation, outside the process line, according to claim 1, characterized in that the increase in free surface energy is carried out by direct treatment of the surface in the plasma of a dielectric barrier, also called a corona, glow, capacitive or silent discharge, for a time of up to 120 s, which burns in a streamer mode - cathodically or anodically directed streamers forming a spatial matrix of randomly distributed microdischarges in the discharge gap. 5. A method for evaluating and managing the susceptibility of porous media to plasma-assisted by prior surface activation technological processes and more specifically to plasma-assisted surface impregnation, outside the technological line, according to claim 1, characterized in that the increase in the free surface energy is carried out by remote treatment of the surface, for a time of up to 120 s, with products from the combustion of a dielectric barrier discharge in air under normal conditions - atmospheric pressure, ambient temperature and humidity, containing chemically active particles (CHAP), with the discharge burning in streamer mode and forms a spatial matrix of microdischarges randomly distributed in the discharge gap. 6. A method for assessing and managing the susceptibility of porous media to plasma-assisted pre-surface activation technological processes and more specifically to plasma-assisted surface impregnation, off the process line, according to claim 2 and 3, characterized in that the dielectric barrier discharge burns in a two- or three-electrode system fed with alternating voltage at an industrial frequency - 50 or 60 Hz, or an increased frequency - up to 1 kHz, as the value of the voltage on the discharge (air, working) gap, with a size of 3 to 24 mm, is between 10 kV rms (amplitude 11.4 kV) and 42 kV rms (amplitude 59 kV). 7. Method for evaluating and managing the susceptibility of porous media to plasma-assisted by preliminary surface activation technological processes and more specifically to plasma-assisted surface impregnation, outside the technological ♦ · · · · · ·* ·»· · · ♦ · 9· • · ······· · · ··· · · · ·· ♦ line according to claim 2, characterized in that* the surface direct plasma treatment is carried out bilaterally and continuously by passing the porous track through the discharge plasma , while the thickness of the processed product does not exceed the size of the discharge gap. 8. A method for evaluating and managing the susceptibility of porous media to plasma-assisted pre-surface activation technological processes, and more specifically to plasma-assisted surface impregnation, off the process line, according to claim 2, characterized in that the surface treatment with products from the combustion of the dielectric barrier discharge, which are distributed in the flow of air passing through the discharge gap, is carried out unilaterally in a semi-open technological system, as a part of the processed surface closes the active volume, and a semi-permeable barrier (brush) allows the continuous processing of the surface "step after step' by its relative motion relative to the active volume. 9. A method for evaluating and managing the susceptibility of porous media to plasma-assisted by preliminary surface activation technological processes and more specifically to plasma-assisted surface impregnation, outside the technological line, according to claim 1, characterized in that the open (technological) time is measured from the moment of completion of the plasma surface activation process to the beginning of the assisted impregnation process for each part of the impregnated surface and takes values from 2 to 24 hours, which allow to synchronize effectively the two processes - of the plasma pre-activation and of the surface impregnation, while preserving, to the necessary extent, the acquired improved surface compliance with the impregnating solution. 10. A method for evaluating and managing the susceptibility of porous media to plasma-assisted by prior surface activation technological processes and more specifically to plasma-assisted surface impregnation, outside the technological line, according to claim 1, characterized in that when impregnating with aqueous solutions of phosphorous flame retardants, the produced protective diffuse coating can be observed optically after developing it by chemical transformation in the temperature range of 185 to 230 °C to form a carbon black layer that allows to evaluate the thickness, integrity and defectivity of the coating when making appropriate cuts - along the direction or across the structure of the porous medium.