RU2743565C1 - Method for increasing the tensile strength of fibrous composites by strengthening the matrix-filler interface of carbon fibers with functionalized carbon nanotubes - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention can be used in the manufacture of composites for aircraft parts. Prepared is a dispersion of functionalized carbon nanotubes (CNTs) containing from not less than 1 to not more than 10% functional groups in n-methylpyrrolidone with a concentration of 20-250 μg / ml. When preparing this dispersion, a solvent with a boiling point of 120-180 °C is additionally added from the group consisting of cyclohexanone, cyclohexanol, cyclopentanone, dimethylacetamide or their mixture taken in a volume ratio from not less than 1:1 to not more than 1:5 to the specified dispersion. The prepared dispersion is applied to the surface of carbon fiber with simultaneous heating of its surface to 60-120 °C by aerosol spraying in the form of separate microdroplets forming a discontinuous uniformly distributed CNT layer. Dispersion consumption does not exceed 0.1 ml / min. Then, with simultaneous heating of the carbon fiber surface to 60-80 °C by aerosol spraying, a hardener containing amino groups is applied, selected from polyethylene polyamine, triethylenetetramine, diethylenetriamine, tetraethylenepentamine, m-xylylenediamine, m-phenylenediamine or a mixture thereof, with a concentration of propanol in or butanol 60-800 μg/ml. Consumption of the hardener solution does not exceed 0.3 ml/min. Before aerosol spraying of these solutions, the carbon fiber surface can be treated with ultraviolet light with a wavelength of 200-400 nm in water vapor for at least 1 min to no more than 15 minutes at ultraviolet radiation intensity of 0.5-100 W/cm2.EFFECT: invention provides increase in the tensile strength of a composite based on carbon fibers with an epoxy matrix by strengthening the interface by forming on their surface a network consisting of functionalized CNTs surrounded by molecules of a hardener chemically interacting with binder molecules.2 cl, 2 ex, 3 dwg

Description

The invention relates to methods for increasing the tensile strength of the formed fibrous composite by strengthening the interface of the carbon fiber-polymer matrix by forming a surface-modifying carbon fiber layer that consists of a uniformly distributed network of functionalized carbon nanotubes and molecules of an organic hardener containing amino groups.

To date, the following methods are known to improve the mechanical strength of a composite material based on carbon fibers using the preliminary deposition of CNTs, which contribute to the strengthening of the carbon fiber-epoxy resin interface.

A known method of forming a transparent conductive film by aerosol spraying of suspensions containing nanofilaments and graphene material [1]. Various metal nanowires, nanorods, nanotubes, metal-oxide nanowires, etc. can be used as fillers for the first suspension. In addition, carbon and other nanotubes can be used. Graphene and its various derivatives such as graphene oxide, reduced graphene oxide, chemically functionalized graphene, etc. can be used as a filler for the second suspension. Spraying can be done in a variety of ways, such as compressed air, electrostatic, electrospinning, ultrasonic spraying, or a combination of these. Two types of aerosol microdroplets can be obtained separately and then deposited on the substrate surface sequentially (for example, metal nanowires are deposited first, after which graphene is deposited) or simultaneously. Nevertheless, in this work, this method does not imply controllability of the degree and uniformity of filling the CNT substrate; moreover, the possibility of using three-dimensional structures such as macroscopic fibers as a substrate is not assumed. Whereas in the proposed method it is possible to control the degree of filling of the surface of the substrate / material on which the functionalized CNTs are applied due to the selection of the solvent formulation and the effective temperature of thermal surface treatment during aerosol deposition.

There is a known method of obtaining a polymer / CNT nanocomposite with oriented CNTs with increased resistance to radiation exposure, mechanical strength, electrical conductivity for space applications, as well as applications of microsystem technology [2]. In this case, it is first supposed to form a polymer solution in the first solvent, then sonicate the solution with CNTs, mix the dissolved polymer with a CNT solution and sonicate the resulting solution for a time sufficient to distribute the CNTs over the entire polymer matrix. Then, it is proposed to apply the composite to the substrate and heat treatment, and the ultrasonic treatment of the polymer / CNT solution is performed in the presence of an alternating magnetic field, and the deposition of the nanocomposite on the substrate and its heat treatment occurs in the presence of a constant magnetic field. The disadvantage of the above method in relation to the proposed for patenting is the need to use expensive magnets, which greatly complicates and increases the cost of the installation, and the resulting products as a whole. In addition, since the deposition of the obtained nanocomposite is carried out by the centrifugation method, this immediately limits the range of substrates used, due to the impossibility of applying any kind of substrates (processed) of the fiber type.

A known method of increasing the mechanical strength of the composite, which includes the preparation of a nanosuspension by introducing CNTs into a thermo-plastic binder under ultrasonic action with an intensity in the cavitation zone in the range from 15 to 25 kW / m ² [3]. Moreover, the dispersion of CNTs in the binder is carried out with simultaneous photographic recording of changes in the color intensity of the nanosuspension. When the nanosuspension reaches the color intensity values corresponding to the values of the normalized degree of dispersion in the range from 0.9 to 0.99, the ultrasonic effect is stopped. The method allows to optimize the degree of dispersion of CNTs in the binder and to shorten the formation time of nanocomposites with increased strength due to the uniform distribution of nanoparticles in the nanocomposite. Nevertheless, this patent does not describe the phenomena occurring at the substrate-matrix (or fiber-matrix) interface and the proposed method provides, in fact, an increase in the strength of the binder, but in the volume of the binder itself, while the strength at the substrate (fiber) interface is the binder does not improve. In addition, it is not specified what type of CNT is used. functionalized or not, so it is impossible to say whether the strength improves at the level of the functional group (on CNTs) - the binder molecule.

A known method of improving the strength during the formation of a three-dimensionally enhanced multifunctional nanocomposite and methods for its manufacture [4]. Three-dimensional reinforcement assumes the presence of a two-dimensional tissue, on the fibers of which CNTs are synthesized, directed almost perpendicular to the plane of the fibers that make up the tissue. The nanocomposite consists of a three-dimensional reinforcement and a surrounding matrix material. An improvement in the mechanical, thermal and electrical properties of the nanocomposite in the transverse direction is shown, as well as an additional improvement in geometric stability with temperature changes and vibrational damping compared to base composites reinforced with only two-dimensional fiber. The configuration options for the nanocomposite during formation can simultaneously perform several functions, such as simultaneously improving properties under thermal and mechanical stress or improving properties under mechanical stress while controlling the state of damage in the nanocomposite. Nevertheless, the method according to this patent, in particular, describes not the deposition, but the synthesis of CNTs on the SiC surface assumes high temperatures, since, in this case, it is carried out by the method of chemical vapor deposition, which assumes synthesis temperatures of the order of 700-900 ° C, which very significantly limits the use of this method, because many materials are not as heat resistant.

A known method for modifying a prepreg [5], consisting of impregnation of a fibrous body obtained by doubling multi-strand threads in one direction or a fiber body obtained by interweaving multi-strand threads in the form of warp threads and thin threads with a matrix resin, while in prepreg on the surface of the filaments are applied dispersed carbon nanotubes. In the invention proposed for patenting, in contrast to [5], it is proposed to apply CNTs and a hardener solution containing amino groups by aerosol spraying. Moreover, the selection of effective solvents for the dispersion of CNTs and a hardener solution significantly affects the distribution of the material during microdroplet deposition during aerosol spraying, which, in turn, improves the distribution of both CNTs and hardener molecules over the carbon fiber surface. Also, the difference is that the application of solutions to carbon fibers occurs with additional heating of the surface in the temperature range from 60 to 120 ° C, which contributes to the effective escape of the residual solvent from the volume of microdroplets, and, consequently, increases the uniformity of the CNT network.

Known work [6], in which the surface of CNTs was successfully modified using UV / ozone treatment and a solution of triethylenetetramine (TETA) for use as a reinforcement for composites with a polymer matrix. Treatment of the nanotube surface with a solution of triethylenetetramine (TETA) promotes sewing to the surface of amino groups, due to the attachment of TETA molecules to the CNT surface. It is shown that the dispersion of nanotubes in an epoxy matrix significantly improved after UV / OZ and TETA treatments due to a change in the thermodynamic characteristics of the nanotube surface from hydrophobic to hydrophilic nature, along with improved chemical interaction between CNTs and the polymer. In contrast to the work described, the method proposed for patenting differs in that it is proposed to use, in contrast to multilayer CNTs (MWCNTs), already functionalized CNTs, which will significantly improve the chemical interaction between the CNTs and the polymer, as well as the reproducibility of the parameters of the formed film. Also in the described work, the main task of the study was to increase the uniformity of the dispersion of MCNTs in the bulk of the epoxy resin. In contrast, aerosol sequential deposition of functionalized CNTs and a solution of TETA (or polyethylene polyamine (PEPA)) on the carbon fiber surface is proposed to strengthen the matrix-filler interface. This solves the problem of uniformity of dispersion of CNTs in the bulk of the epoxy resin without deteriorating the parameters of the formed composite structure. Proposed for patenting a method for preliminary treatment of the substrate surface, in which the carbon fiber surface is additionally subjected to ultraviolet treatment in water vapor for at least a minute and up to 15 minutes before applying solutions, at an ultraviolet radiation intensity in the range from 0.5 to 100 W / cm ² and a source wavelength in the range from 200 to 400 nm, is also different from that described in the patent [6], in which the treatment is carried out in a flowing ozone atmosphere, ultraviolet radiation is generated by light pulses from a xenon flash lamp excited by current pulses. In contrast to [6], continuous irradiation of the carbon fiber surface with a high-pressure mercury lamp, for example, DRT-400, is proposed. At the same time, the result of the proposed treatment of the carbon fiber surface is a significant improvement in the interaction of carbon fiber-CNT and CNT-hardener molecule. This, among other things, leads to improved adhesion when gluing the fiber to the matrix. Moreover, this method does not require any chemicals, is carried out at room temperature, and can be performed very quickly.

A feature of the methods for increasing the mechanical strength in the above patents [1-6] is the use of certain nanoscale materials, which in most of the works are dispersed in the volume of the binder, which, although it leads to an improvement in the strength of the entire composite, does not solve the problem of increasing the adhesion of the binder. to the carbon fiber surface, if it is necessary to form composites based on carbon fibers, and also reduces the reproducibility of the uniform distribution of modifying additives in the form of CNTs in the bulk of the composite, due to the complexity of dispersing CNTs and deposition from unstable colloidal solutions.

In the patent [7], which is a prototype of the invention proposed for patenting, it is proposed to increase the mechanical strength of a composite structure based on carbon fibers and an epoxy matrix, preliminary deposition on carbon fibers of carbon nanotubes and curing agent molecules selected from aminoethylpiperazine and pentaethylenehexamine. In this case, the concentration of CNTs was selected in the range from 20 to 500 μg / ml, and the concentration of the curing agent was in the range from 150 to 200 μg / ml. The proposed invention proposes the sequential application of functionalized CNTs and a hardener selected from polyethylene polyamine or triethylenetetramine or diethylenetriamine or tetraethylenepentamine or m-xylylenediamine or m-phenylenediamine or mixtures thereof. It is proposed to use, instead of applying by dipping, application by the aerosol method with simultaneous heating of the surface, for example, using an infrared lamp, of carbon fibers, which contributes to the uniform application of CNTs due to the microdroplet deposition mode and the rapid drying of the residual solvent from the volume of the applied microdroplets. In this case, the concentration of CNTs should be in the range from 20 to 250 μg / ml. The main difference from the prototype is that the application of a CNT dispersion is carried out from a solution containing solvents with a boiling point of 120 to 180 ° C or mixtures thereof, which ensures uniform distribution of the network of functionalized CNTs over the carbon fiber surface. Subsequent deposition of amino group molecules on CNTs in an amount sufficient for the complete binding of all CNTs and not exceeding the amount of CNTs on the surface contributes to a significant strengthening of the matrix-filler interface during the formation of a fibrous composite.

Disclosure of invention

The technical problem of the present invention is to increase the tensile strength of the formed fibrous composite due to the deposition of a network of functionalized carbon nanotubes on the surface of the carbon fiber and subsequent binding of CNTs to molecules containing amino groups.

The technical result is the development of a method for forming a network of functionalized carbon nanotubes associated with carbon fiber and surrounded by molecules of the hardener, chemically interacting with the molecules of the binder.

The uniformity of distribution of CNTs over the surface of carbon fiber without the formation of conglomerates is ensured by the selection of effective solvents with different boiling points and deposition in a microdroplet mode, which ensures complete drying of the deposited microdroplets in one deposition iteration, without redistribution of microdroplets over the surface of the carbon fiber. Subsequent aerosol application of the curing agent in an amount sufficient to completely cover the deposited CNTs, but not exceeding their amount on the carbon fiber surface, leads to an increase in the strength of the entire fibrous composite, due to the interaction of functionalized CNTs with amino groups present in the curing agent, which chemically interact with epoxy groups in epoxy resin - a binder.

In the method proposed for patenting, the concentration of CNTs in the solution is selected based on the need to cover the carbon fiber surface with a uniform grid of misoriented CNTs, while ensuring acceptable uniformity. An increase in the concentration of CNTs in solution, higher than that proposed (250 μg / ml) in the invention, leads to an increase in the instability of the system as a whole (the formation of conglomerates and precipitation of the solution), and also leads to the complexity of application by an aerosol method, which leads to a non-uniform distribution of CNTs over surface of carbon fibers. The lower concentration limit (20 μg / ml) is defined as the minimum possible concentration for the formation of a CNT network by aerosol spraying, a decrease in concentration below 20 μg / ml leads to the formation of areas completely free of CNTs and is economically unjustified, due to the duration of the nanotube layer for uniform formation. CNT networks, since at this concentration, almost one solvent is applied. To prepare a dispersion of CNTs, functionalized CNTs are used, which contain from not less than I% to not more than 10% functional, such as carboxyl and hydroxyl, groups (according to the manufacturer's data - Sigma-Aldrich), while preparing a dispersion of carbon nanotubes for aerosol deposition additionally add a solvent with a boiling point in the range from 120 to 180 ° C or a mixture thereof, from the following list: cyclohexanone, cyclohexano l, cyclolentanone, dimethylacetamide; which is in a volume ratio from not less than 1: 1 to not more than 1: 5 to the dispersion of CNTs in n-methylpyrrolidone (the structural formulas of the solvents are shown in Fig. 1.). The presence of functional groups on the CNT surface enhances the binding of CNTs both to the carbon fiber surface and to the hardener molecules and epoxy groups of the polymer matrix. The main solvent for the CNT dispersion is n-methylpyrrolidone (NMP), the temperature of which is 202 ° C. When using the aerosol microdroplet mode of applying the solution, it is necessary to ensure the effective escape of the solvent from individual microdroplets on the carbon fiber surface while maintaining the hydrophobicity of the surface, at which there is no spreading of drops and redistribution of CNTs over the carbon fiber surface (Fig. 2). Adding a low-temperature solvent from the list: cyclohexanone, cyclohexanol, cyclopentanone, dimethylacetamide; reduces not only the size of microdroplets, but also increases the rate of their drying, contributing to the formation of a uniform network of CNTs (Fig. 3.). Two solvents with different boiling points were selected on the basis that the aerosol application process is carried out by pumping compressed air or an inert gas through a spray nozzle, which leads to a significantly higher rate of residual solvent leaving the sprayed microdroplets when using only a solvent with a low temperature boiling. In this case, the selected volume ratios of the addition of solvents from 1: 1 to no more than 1: 5 is due to the fact that when an additional solvent is added to the NMP solution in a volume ratio of less than 1: 1, it does not lead to any noticeable changes in the character of drying of microdroplets. While an excess of more than 1: 5 in the volumetric ratio of solvents leads to too strong evaporation of solvents, due to the fact that most of the low-temperature solvent dries up in the course of aerosol spraying, and, consequently, to inhomogeneous deposition of CNTs over the carbon fiber surface.

The addition of curing agent molecules with amino groups to the CNT solution is necessary for coating the CNTs with curing agent molecules and binding to functional groups to further improve the interfacial interaction of carbon fiber and polymer matrix. The range of concentrations in the described invention is selected taking into account the effective full interaction of all CNTs with the hardener molecules, without finding the hardener molecules in free form. The choice of curing agent molecules from polyethylenepolyamine or triethylenetetramine or diethylenetriamine or tetraethylenepentamine or m-xylylenediamine or m-phenylenediamine or their mixtures having amino groups is explained by the prospect of improving the bond of amino groups with epoxy groups of epoxy resin.

A hardener solution for aerosol application is prepared in a solution of 2-propanol or butanol with concentrations ranging from at least 60 μg / ml to not more than 800 μg / ml. The lower limit of the hardener concentration is due to the fact that the fraction of hardener molecules at less than 60 μg / ml on the carbon fiber surface does not provide an arbitrarily noticeable effect on the binding of CNT functional groups with epoxy groups and carbon fiber. In this case, exceeding the concentration of more than 800 μg / ml leads to a decrease in the strength of the interphase boundary due to the presence of hardener molecules not associated with CNTs and thus the formation of defects in the composite. Along the border of which a rupture occurs during deformation of the fiber composite.

The additional processing temperature should not exceed the boiling point of the solvents used in the solution, which can adversely affect the deposition of CNTs on the carbon fiber surface, including due to the evaporation of the solvent from the bulk and, as a consequence, changes in the final concentration of CNTs and the nature of CNT dispersion over the carbon fiber surface. Heating the carbon fiber surface during aerosol spraying using an infrared heater ensures uniform heating of the carbon fiber. In this case, the selected temperature range from 60 to 80 ° C is due to the solvents used and their effective rate of evaporation from the volume of microdroplets.

In the proposed patenting method, it is also proposed to additionally process the surface of the carbon fiber before the operation of applying solutions with ultraviolet radiation in water vapor for at least a minute and up to no more than 15 minutes, with an ultraviolet radiation intensity in the range from 0.5 to 100 W / cm ² and length source waves in the range from 200 to 400 nm. Treatment of the carbon fiber surface with ultraviolet light is possible using a high-pressure mercury lamp, for example, DRT-400. In this case, carbon fiber is placed at a distance of 5 centimeters relative to the plane of the lamp, for processing efficiency, which is due to the radiation intensity of the DRT-400 lamp. The time range is due to the fact that with a processing time of less than one minute, the number of functional groups on the surface of carbon fiber grafted in this way does not make a significant effect on the nature of the interaction between carbon fiber / CNT / polymer matrix, while exceeding the processing time of more than 15 minutes leads to degradation structure of carbon fiber, due to the high intensity of processing. It is proposed to use a cuvette, which is located along the processed carbon fiber, containing at least 20 ml of distilled water. In this case, additional heating of the cuvette is not required to increase the evaporation rate. Surface treatment should be carried out in a closed box or chamber with dimensions not exceeding 300 × 300 × 300 (W × D × H), which is associated with the need to localize water vapor over the sample. The result of the proposed surface treatment of carbon fiber is a significant improvement in the wetting of the fibers with the matrix, adhesion and adhesion of the fiber to the polymer matrix. Moreover, this method does not require any chemicals, is carried out at room temperature, and can be performed very quickly. At the same time, this method is easily scalable for the technological production and processing of large area carbon fibers.

Experiments to measure the tensile strength of the formed modified composite material according to Example 1 (based on carbon fibers with an epoxy matrix by preliminary modification of the carbon fiber surface with a formed layer of carbon nanotubes and hardener molecules) showed an increase in the tensile strength of the modified composite material (E _{max_mod} = 3640 MPa) with respect to to the unmodified composite material (P _{max_clean} = 3166 MPa) by 15%, in the absence of deterioration of E _modes for the modified composite (E _pure = 167 GPa) at E _mod = 166 GPa for the unmodified composite.

The invention is illustrated by graphic materials:

FIG. 1 shows the structural formulas of the solvents: cyclohexanone, cyclohexanol, cyclopentanone, dimethylacetamide, additionally added to the dispersion of CNTs in n-methylpyrrolidone.

FIG. 2. The result of the invention is presented, in which a surface-modifying misoriented network of functionalized carbon nanotubes is applied to the carbon fiber by aerosol spraying from a solution of n-methylpyrrolidone.

FIG. 3 shows the result of the invention, in which a surface-modifying misoriented network of functionalized carbon nanotubes is applied to the carbon fiber by aerosol spraying from a solution of n-methylpyrrolidone with the addition of a low-boiling solvent cyclohexanone in a volume ratio of 1: 3.

An example of the invention

Example 1.

The preparation of solution No. 1 for the deposition of carbon nanotubes is carried out by preparing a dispersion of CNTs (containing 10% functional groups) in n-methylpyrrolidone (NMP) and cyclohexanone with a CNT concentration of 100 μg / ml. The volume ratio of NMP and cyclohexanone is 1: 3. The solution is additionally processed in an ultrasonic bath for 5 minutes at 47 kHz ultrasound parameters.

Preparation of solution No. 2 for applying the hardener is carried out by preparing a solution of the hardener triethylenetetramine in a solution of 2-propanol, with a concentration of 200 μg / ml. The solution is additionally processed in an ultrasonic bath for 1 minute at 47 kHz ultrasound parameters.

Application of solution No. 1 is carried out by aerosol spraying, and the flow rate of the solution does not exceed 0.1 ml / min. The processing temperature during application is 90 ° C using an IR heater.

After application of solution No. 1, application of solution No. 2 is carried out by aerosol spraying, and the flow rate of the solution does not exceed 0.3 ml / min. The processing temperature during application is 80 ° C using an IR heater.

The method allows to form on the surface of carbon fibers a misoriented CNT network covered with hardener molecules (photo in Fig. 3).

Example 2.

The preparation of solution No. 1 for applying carbon nanotubes is carried out by preparing a dispersion of CNTs (containing 5% functional groups) in n-methylpyrrolidone (NMP) and cyclohexanone with a CNT concentration of 150 μg / ml. The volume ratio of NMP and cyclohexanone is 1: 4. The solution is additionally processed in an ultrasonic bath for 5 minutes at 47 kHz ultrasound parameters.

Preparation of solution No. 2 for applying the hardener is carried out by preparing a solution of the hardener triethylenetetramine in a solution of butanol, with a concentration of 300 μg / ml. The solution is additionally processed in an ultrasonic bath for 1 minute at 47 kHz ultrasound parameters.

Previously, before applying the solutions, the carbon fiber surface is treated in ultraviolet light in water vapor for 10 minutes, at an ultraviolet radiation intensity in the range of 30 W / cm ² , which is achieved using a DRT-400 lamp with a sample located at a distance of 5 cm from the lamp plane.

Application of solution No. 1 is carried out by aerosol spraying, and the flow rate of the solution does not exceed OD ml / min. The processing temperature during application is 90 ° C using an IR heater.

After application of solution No. 1, application of solution No. 2 is carried out by aerosol spraying, and the flow rate of the solution does not exceed 0.3 ml / min. The processing temperature during application is 80 ° C using an IR heater. The method allows to form on the surface of carbon fibers a misoriented CNT network covered with hardener molecules.

Repeating the procedure for applying solutions No. 1 and No. 2 of examples 1-2, the concentration of CNTs (containing up to 10% functional groups) was varied in the range from 20 μg / ml or less to 250 μg / ml or more in n-methylpyrrolidone with the addition of various solvents with boiling point from 120 to 180 ° С from the group cyclohexanone, cyclohexanol, cyclopentanone, dimethylacetamide (structural formulas in Fig. 1) separately or in a mixture, while the additive is in a volume ratio from not less than 1: 1 to not more than 1: 5 to the main dispersion of CNTs (in n-methylpyrrolidone). The flow rate of the solution did not exceed 0.1 ml / min. After impregnation of carbon fiber with any of the above-mentioned compositions of solution No. 1, heat treatment of the carbon fiber surface was carried out at a temperature in the range from 45 ° C to 120 ° C. The concentrations of various hardeners (with amino groups) also varied: polyethylene polyamine, triethylenetetramine, diethylenetriamine, tetraethylenepentamine, m-xylylenediamine, m-phenylenediamine, both separately and in their mixture, in a solution of 2-propanol or butanol in the range from 60 μg / ml or less up to 800 μg / ml or more. The flow rate of solution No. 2 did not exceed 0.3 ml / min. After impregnation of carbon fiber with any of the above-mentioned solutions of the hardener, the carbon fiber surface was heat treated at a temperature in the range from 60 to 80 ° C. For a more effective modification of the fibrous composite, before the process of sequential aerosol application of solutions No. 1 and No. 2, the carbon fiber surface was additionally treated with ultraviolet light in water vapor for at least 1 minute and up to no more than 15 minutes, at an intensity of ultraviolet radiation in the range from 0.5 up to 100 W / cm ² and a source wavelength in the range from 200 to 400 nm.

The quality of modification of the composite carbon fiber material in all experiments was monitored photographically. A composite obtained by aerosol spraying of CNTs from a solution of n-methylpyrrolidone (Fig. 2) was used as a reference sample. When the parameters went beyond the stated limits, a violation of the inhomogeneity of the formed layer of functionalized CNTs with a hardener was observed.

Sources of information

1. US patent US 8871296 B2.

2. Patent of Russia RU 2 400 462 С1

3. Patent of Russia RU 2 500 695 С1

4. Patent CA 2632202 C

5. Japan patent JP 2007070593 A

6. Sham M.L., Kim J.K. Surface functionalities of multi-wall carbon nanotubes after U V / Ozone and TETA treatments // Carbon. - 2006. - T. 44. - No. 4. - S. 768-777.

7. Russian patent RU 2703635 (prototype).

Claims (3)

1. A method for increasing the tensile strength of fibrous composites by strengthening the matrix-filler interface of carbon fibers with functionalized carbon nanotubes (CNTs), which are applied to the surface of carbon fiber from solutions containing carbon nanotubes, as well as curing agent molecules containing amino groups, characterized in that what A dispersion of CNTs in n-methylpyrrolidone is applied by aerosol spraying in the form of individual microdrops, forming a discontinuous uniformly distributed layer of CNTs on the carbon fiber surface, and the flow rate of the dispersion does not exceed 0.1 ml / min, the concentration of carbon nanotubes in the dispersion is from 20 to 250 μg / ml, and the process of applying the CNT dispersion is carried out with simultaneous heating of the carbon fiber surface to a temperature in the range from 60 to 120 ° C; in this case, functionalized carbon nanotubes are used to modify the carbon fiber surface, which contain from at least 1% to not more than 10% functional groups, and when preparing a dispersion of carbon nanotubes for aerosol deposition, a solvent with a boiling point of 120 to 180 ° C or a mixture thereof is additionally added , from the following group: cyclohexanone, cyclohexanol, cyclopentanone, dimethylacetamide, which is in a volume ratio from not less than 1: 1 to not more than 1: 5 to the dispersion of CNTs in n-methylpyrrolidone; then additionally by aerosol spraying, a hardener is applied, selected from polyethylene polyamine, or triethylenetetramine, or diethylenetriamine, or tetraethylenepentamine, or m-xylylenediamine, or m-phenylenediamine, or a mixture thereof, with a concentration of 2-propanol or butanol in a solution / from 60 to 800 μg ml, and the flow rate of the solution does not exceed 0.3 ml / min; the process of applying the hardener solution is carried out with simultaneous heating of the carbon fiber surface at a temperature in the range from 60 to 80 ° C. 2. The method according to claim 1, characterized in that before the process of aerosol application of solutions, the surface of the carbon fiber is additionally subjected to treatment with ultraviolet light in water vapor for at least a minute and up to no more than 15 minutes, at an intensity of ultraviolet radiation in the range from 0.5 to 100 W / cm ² and a source wavelength in the range from 200 to 400 nm.

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