CN117211009A - Composite material and preparation method thereof - Google Patents

Abstract

This application relates to the technical field of new materials, and in particular to a composite material and a preparation method thereof. The components of the composite material include modified flax fiber and polypropylene fiber, both of which are constructed into a three-dimensional fiber network structure; in terms of parts by mass, the composite material The modified flax fiber is 30 to 50 parts, the polypropylene fiber is 50 to 70 parts, and the modified flax fiber is flax fiber modified by isomerized terpene resin. The composite material components provided by this application include modified flax fiber and polypropylene fiber. Among them, the flax fiber in the modified flax fiber component has the advantages of low acquisition cost, low density, green degradability, etc., which can further reduce the density and carbon content of the composite material. Emissions; and, modified flax fiber is flax fiber modified with isomerized terpene resin, so that polypropylene fiber and modified flax fiber can form a three-dimensional fiber network structure with three forces after heating and compounding, so that the composite material has high Bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance.

Description

Composite materials and preparation methods thereof

【Technical field】

The present application relates to the technical field of new materials, and in particular to a composite material and a preparation method thereof.

【Background technique】

With the emergence of global energy crisis, climate change and other issues, and in response to the call of national low-carbon and renewable energy policies, lightweighting, renewable raw materials and low-carbon emissions have become the development trend of automotive structural materials in the automotive industry. In order to meet the development trend, automobile structural materials are usually composed of minerals and polymers such as polypropylene, ABS, PC/ABS filled in the minerals. The density of the above-mentioned automobile structural materials is usually around 1.0~1.1g/ ^cm3 . There is a certain amount of space for lightweighting when used heavily in cars.

However, the minerals in the above-mentioned automotive structural materials are derived from ores, and the polymer composite materials are derived from petroleum. Both ores and petroleum are non-renewable in the short term. In the process of obtaining raw materials, mining of ores will destroy the land, and the process of refining petroleum produces high carbon emissions.

[Content of the invention]

In view of this, this application provides a composite material and a preparation method thereof. The composite material is obtained by compounding low-density and green degradable modified flax fiber and polypropylene fiber. The composite material has the characteristics of green degradability, low carbon emissions, High bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance.

In a first aspect, the application provides a composite material. The components of the composite material include modified flax fiber and polypropylene fiber, and the modified flax fiber and the polypropylene fiber are constructed into a three-dimensional fiber network structure;

Among them, in terms of parts by mass, the modified flax fiber in the composite material is 30 to 50 parts, the polypropylene fiber in the composite material is 50 to 70 parts, and the modified flax fiber is isomerized Terpene resin modified flax fiber.

In the above solution, the composite material components provided by this application include modified flax fiber and polypropylene fiber. Among the modified flax fiber components, flax fiber has the advantages of low acquisition cost, low density, green degradability, etc., which can further reduce The overall density and carbon emissions of the composite material; at the same time, the modified flax fiber is a flax fiber modified by isomerized terpene resin. This composition allows the polypropylene fiber and the modified flax fiber to form a three-dimensional three-dimensional force after heating and compounding. Fiber network structure, and thus the composite material has high bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance.

Combined with the first aspect, the density of the composite material is ≤1.02g/cm ³ .

In the above scheme, the density of the composite material will affect the mass of the final prepared automobile structure. The greater the density of the composite material, the heavier the composite material will be per unit volume. If the density of the composite material is too high, the prepared automobile structure cannot achieve lightweight effect.

Combined with the first aspect, the tensile strength of the composite material is ≥29MPa.

In the above scheme, tensile strength refers to the maximum tensile force that the composite material can withstand after tensile deformation. The greater the tensile strength, the greater the tensile stress that the composite material can withstand. If the tensile strength of the composite material is too small, the composite material will be easily damaged during processing (such as stretch molding) into an automobile structure, and the prepared automobile structure will have poor tensile properties.

Combined with the first aspect, the bending strength of the composite material is ≥37MPa.

In the above scheme, bending strength refers to the maximum stress that the composite material can withstand when it breaks under bending load or reaches a specified bending moment. The greater the bending strength, the greater the bending load force that the composite material can withstand. If the bending strength of the composite material is too low, the hardness of the prepared automobile structure will be low, and it will be prone to damage when the force it withstands is too large.

Combined with the first aspect, the flexural modulus of the composite material is ≥1940Mpa.

In the above scheme, the flexural modulus refers to the ability of the composite material to resist deformation under bending load. The greater the flexural modulus, the more difficult it is for the composite material to deform. If the flexural modulus of the composite material is too low, the hardness of the prepared automobile structure will be low and it will easily deform during use, which will affect the use of the automobile structure.

Combined with the first aspect, the notched impact strength of the composite material is ≥5.6kJ/m ² .

In the above scheme, notched impact strength refers to the energy absorbed per unit cross-sectional area when a notched composite material breaks or breaks under the action of impact load. The greater the notched impact strength, the lower the brittleness and stronger toughness of the composite material. . If the notched impact strength of the composite material is too low, the automobile structure made of the composite material will have defects such as notches during use. At this time, it will easily break or crack when exposed to external forces, which will affect the use of the automobile structure.

Combined with the first aspect, the low-temperature impact strength of the composite material at -40°C is ≥4.7kJ/m ² .

In the above scheme, low-temperature impact strength refers to the energy absorbed by unit cross-sectional area when the composite material is broken or broken under the action of impact load at low temperature. The greater the low-temperature impact strength, the lower the brittleness and toughness of the composite material under low-temperature conditions. powerful. If the low-temperature impact strength of the composite material is too low, the automobile structure made of the composite material will be prone to breakage or cracking when exposed to external forces when used in an environment with large temperature changes, which will affect the use of the automobile structure.

Combined with the first aspect, the components of the composite material include modified flax fiber and polypropylene fiber, and the modified flax fiber and the polypropylene fiber are constructed into a three-dimensional fiber network structure;

Among them, in terms of parts by mass, the modified flax fiber in the composite material is 50 parts, the polypropylene fiber in the composite material is 50 parts, and the modified flax fiber is modified by isomerized terpene resin. Sexy flax fiber.

In the above scheme, the component parameters of the composite material are controlled within the above range, and the density of the obtained composite material is around 0.90g/ ^cm3 , the tensile strength is ≥30MPa, the flexural modulus is ≥3500MPa, and the notch impact is ≥8kJ/ ^m2 .

In a second aspect, the present application provides a method for preparing a composite material. The preparation method includes the following steps:

In terms of parts by mass, 30 to 50 parts of modified flax fiber and 50 to 70 parts of polypropylene fiber are subjected to a premixing process to obtain the first mixed material; wherein the modified flax fiber is modified with isomerized terpene resin. sexual flax fiber;

The first mixed material is subjected to an opening process, a carding process and an air-laying process to obtain a second mixed material;

The second mixed material is subjected to a heating needling process to obtain a composite material with a three-dimensional fiber network structure.

In the above scheme, modified flax fiber is used as the raw material of the composite material. The modified flax fiber is flax fiber modified by isomerized terpene resin, so that when the modified flax fiber and polypropylene fiber are heated and pressurized during the preparation process, The two can form a strong link structure, which improves the binding force of modified flax fiber and polypropylene fiber. At the same time, the preparation process also adopts a heating acupuncture process. Through the heating acupuncture process, the modified flax fiber and polypropylene fiber can be interwoven into The more stable and dense three-dimensional fiber network structure greatly reduces the voids inside the composite material, thereby enhancing the tensile strength, flexural strength, flexural modulus, and impact resistance of the composite material.

Combined with the second aspect, the fiber length of the polypropylene fiber is 100 mm to 150 mm.

In the above solution, the length of the polypropylene fiber will affect the strength of the composite material. If the length of the polypropylene fiber is within the above range, the prepared composite material will have strong toughness.

Combined with the second aspect, the fiber diameter of the polypropylene fiber is 10 μm to 50 μm.

In the above solution, the diameter of the polypropylene fiber will affect the strength of the composite material. If the diameter of the polypropylene fiber is within the above range, the prepared composite material will have strong toughness.

Combined with the second aspect, the time of the pre-mixing process is 3 to 5 minutes.

In the above scheme, if the premixing time is too short, it will be difficult to mix the modified flax fiber and polypropylene fiber evenly, which is not conducive to subsequent processes; if the premixing time is too long, the energy consumption for the preparation of composite materials will increase, thereby increasing the The cost of composite material preparation.

Combined with the second aspect, the temperature of the heating needling process is 140°C to 160°C.

In the above scheme, if the temperature of the heating acupuncture process is too high, when the modified flax fiber infiltrates the polypropylene fiber, the fluidity will be too large, affecting the uniformity of the infiltration; if the temperature of the heating acupuncture process is too low, the modified flax fiber will infiltrate the polypropylene fiber. fiber, the fluidity is too low and cannot effectively penetrate into the polypropylene fiber, which will also affect the uniformity of infiltration;

Combined with the second aspect, the heating acupuncture process includes the following steps:

The acupuncture process, the winding forming process of the modified flax fiber and the polypropylene fiber, the process of soaking the polypropylene fiber with the modified flax fiber, and the melted modified flax fiber bonding with the polypropylene fiber to form a third mixture Material process, the third mixed material undergoes a winding, braiding and solidification process.

In the above solution, through the steps of the heating acupuncture process, a more stable and dense three-dimensional fiber network structure can be constructed, which greatly reduces the voids inside the composite material and enhances the performance of the composite material.

Combined with the second aspect, the preparation method also includes a preparation process of the modified flax fiber:

The flax fiber is subjected to an opening process, and then the dissolved isomerized terpene resin solution is sprayed on the flax fiber, and after standing, the modified flax fiber is obtained.

In the above solution, through the above preparation method, modified flax fiber that meets the application requirements of the present application can be obtained, and has stronger binding force with polypropylene fiber.

Combined with the second aspect, in terms of parts by mass, the mass of the isomerized terpene resin is 1% to 10% of the mass of the flax fiber.

In the above scheme, if the mass content of the isomerized terpene resin is within the above range, the modified flax fiber with strong binding force of the present application can be obtained.

Combined with the second aspect, the isomerized terpene resin is an isomer of β-pinene, terpene and hydrocarbon compounds or copolymers catalyzed by iodine or zinc at 200 to 260°C.

In the above solution, through the above preparation method, an isomerized terpene resin that meets the usage requirements of the present application can be obtained and used for the preparation of modified flax fiber.

Combined with the second aspect, the density of the composite material is ≤1.02g/cm ³ .

In the above scheme, the density of the composite material will be related to the mass of the final prepared automobile structure. The greater the density of the composite material, the heavier the composite material per unit volume will be. If the density of the composite material is too high, the prepared automobile structure cannot achieve lightweight effect.

Combined with the second aspect, the tensile strength of the composite material is ≥29MPa.

In the above scheme, the tensile strength is the maximum tensile force that the material can withstand after tensile deformation. The greater the tensile strength, the greater the tensile stress that the composite material can withstand. If the tensile strength of the composite material is too small, the composite material will be easily damaged during processing (such as stretch molding) into an automobile structure, and the prepared automobile structure will have poor tensile properties.

Combined with the second aspect, the flexural strength of the composite material is ≥37MPa.

In the above scheme, bending strength refers to the maximum stress that the composite material can withstand when it breaks under bending load or reaches a specified bending moment. The greater the bending strength, the greater the bending load force that the composite material can withstand. If the bending strength of the composite material is too low, the hardness of the prepared automobile structure will be low, and it will be prone to damage when the force it withstands is too large.

Combined with the second aspect, the flexural modulus of the composite material is ≥1940Mpa.

In the above scheme, the flexural modulus refers to the ability of the composite material to resist deformation under bending load. The greater the flexural modulus, the more difficult it is for the composite material to deform. If the flexural modulus of the composite material is too low, the hardness of the prepared automobile structure will be low and it will easily deform during use, which will affect the use of the automobile structure.

Combined with the second aspect, the notched impact strength of the composite material is ≥5.6kJ/m ² .

In the above scheme, notched impact strength refers to the energy absorbed per unit cross-sectional area when a notched composite material breaks or breaks under the action of impact load. The greater the notched impact strength, the lower the brittleness and stronger toughness of the composite material. . If the notched impact strength of the composite material is too low, the automobile structure made of the composite material will have defects such as notches during use. At this time, it will easily break or crack when exposed to external forces, which will affect the use of the automobile structure.

Combined with the second aspect, the low-temperature impact strength of the composite material at -40°C is ≥4.7kJ/m ² .

In the above scheme, the low-temperature impact strength refers to the energy absorbed by the unit cross-sectional area when the composite material breaks or fractures under the action of impact load at low temperature. The greater the low-temperature impact strength, the lower the low-temperature condition, the lower the brittleness and toughness of the composite material. powerful. If the low-temperature impact strength of the composite material is too low, the automobile structure made of the composite material will be prone to breakage or cracking when exposed to external forces when used in an environment with large temperature changes, which will affect the use of the automobile structure.

Using the above solution, this application has the following beneficial effects:

The composite material provided by this application has components including modified flax fiber and polypropylene fiber. Among the components of the modified flax fiber, flax fiber has the advantages of low acquisition cost, low density, green degradability, etc., which can reduce the cost of the composite material. Overall density and carbon emissions; at the same time, modified flax fiber is flax fiber modified with isomerized terpene resin. This composition allows polypropylene fiber and modified flax fiber to form a three-dimensional fiber network with three forces after heating and compounding. Structure, and thus composite materials have high bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance.

In the preparation method of composite materials provided by this application, modified flax fiber is used as the raw material of the composite material. The modified flax fiber is flax fiber modified by isomerized terpene resin, so that the modified flax fiber and polypropylene fiber are in the preparation process. When heated and pressurized, the two can form a strong link structure with triple forces, which improves the bonding force between modified flax fiber and polypropylene fiber. At the same time, the preparation process also adopts a heated acupuncture process. Through the heated acupuncture process, it can Interweaving modified flax fiber and polypropylene fiber into a more stable and dense three-dimensional fiber network structure greatly reduces the voids inside the composite material, thereby enhancing the tensile strength, flexural strength, flexural modulus, and impact resistance of the composite material.

【Detailed ways】

It should be clear that the described embodiments are only some of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of this application.

The terminology used in the embodiments of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application. As used in the embodiments and the appended claims, the singular forms "a," "the" and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

It should be understood that the term "and/or" used in this article is only an association relationship describing related objects, indicating that there can be three relationships, for example, A and/or B, which can mean: A alone exists, and A and A exist simultaneously. B, there are three situations of B alone. In addition, the character "/" in this article generally indicates that the related objects are an "or" relationship.

With the emergence of global energy crisis, climate change and other issues, and in response to the call of national low-carbon and renewable energy policies, lightweighting, renewable raw materials and low-carbon emissions have become the development trend of automotive structural materials in the automotive industry. In order to meet the development trend, automobile structural materials are usually composed of minerals and polymers such as polypropylene, ABS, PC/ABS filled in the minerals. The density of the above-mentioned automobile structural materials is usually around 1.0~1.1g/ ^cm3 . There is a certain amount of space for lightweighting when used heavily in cars.

However, the minerals in the above-mentioned automotive structural materials are derived from ores, and the polymer composite materials are derived from petroleum. Both ores and petroleum are non-renewable in the short term. In the process of obtaining raw materials, mining of ores will destroy the land, and the process of refining petroleum produces high carbon emissions.

In the existing technology, coconut palm fiber, hemp fiber, and oil/oil-free polypropylene short fiber are used as raw materials. After opening, breaking up, fully mixing, carding, web forming, and needling, composite materials are made. This composite material has Anti-corrosive, non-mildew, antibacterial, breathable, and cost-effective. However, the disadvantage of this method is that there are a large number of hydroxyl groups on the surface of coconut palm fiber and hemp fiber. The hydroxyl groups are hydrophilic, while the surface of polypropylene is hydrophobic, resulting in poor compatibility between coconut palm fiber, hemp fiber and polypropylene. The composite material obtained by this simple blending has weak bonding force, and the automobile structure formed after hot pressing has a large number of voids inside and the strength is not high.

In addition, maleic anhydride is also used to graft polypropylene, and epoxy resin is used to modify the polypropylene to increase the compatibility between polypropylene and hemp fiber. After mixing, opening, air-laying, needle punching, Composite materials are made by soaking in water, extruding, drying, and hot pressing. This composite material has good mechanical properties. However, the shortcomings of this method are: the preparation of composite materials requires a long cycle and high energy consumption. The extrusion time requires at least 3 hours. After the extrusion is completed, it takes at least several hours to dry completely. Due to the hemp fiber It is water-absorbent. If it is not completely dried, there will be a large amount of moisture inside, which will form voids and defects inside the composite material during the hot pressing process, reducing the performance of the composite material. Moreover, polypropylene and epoxy resin are incompatible systems. The function of maleic anhydride-grafted polypropylene in the formula is to increase the compatibility between polypropylene and epoxy resin, and to enhance the compatibility between polypropylene and hemp fiber. Relying on the curing effect of epoxy resin, a two-ring link structure is formed. The link structure is long, but the bonding force is limited and it is easy to break.

Therefore, it is of great significance to find a composite material that is lightweight, environmentally friendly and has excellent performance.

In view of this, this application provides a composite material. The components of the composite material include modified flax fiber and polypropylene fiber, and the modified flax fiber and polypropylene fiber are constructed into a three-dimensional fiber network structure;

Among them, in terms of parts by mass, the modified flax fiber in the composite material is 30 to 50 parts, the polypropylene fiber in the composite material is 50 to 70 parts, and the modified flax fiber is flax fiber modified by isomerized terpene resin.

In the above solution, the composite material components provided by this application include modified flax fiber and polypropylene fiber. Among the modified flax fiber components, flax fiber has the advantages of low acquisition cost, low density, green degradability, etc., which can further reduce The overall density and carbon emissions of the composite material; at the same time, the modified flax fiber is a flax fiber modified by isomerized terpene resin. This composition allows the polypropylene fiber and the modified flax fiber to form a triple force after heating and compounding. With the three-dimensional fiber network structure, the composite material has high bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance.

Specifically, because there are a large number of hydrophilic hydroxyl groups on the surface of modified flax fiber and the surface of polypropylene fiber is hydrophobic, the compatibility between modified flax fiber and polypropylene fiber is poor. When the two are combined, they mainly rely on the modification of polypropylene fiber. The physical wrapping force of flax fiber and the binding force between the two are small. When force is applied, the composite flax fiber and polypropylene fiber are easily peeled off. At the same time, terpene resin has a good viscosity-increasing effect because it can quickly penetrate into the material to be bonded and can be used in the adhesion process of materials. However, terpene resin without isomerization has no compatibility with flax fiber. not good. Therefore, the isomerized terpene resin is used in this application. The isomerized terpene resin is completely compatible with the flax fiber. When the isomerized terpene resin and the flax fiber are extruded and spun together, a mutually soluble terpene resin is formed. And the modified flax fiber and polypropylene fiber are evenly mixed with the modified flax fiber. During the mixing process, through the action of heating and low pressure, the isomerized terpene resin with a low softening point has good fluidity and has good effects on the polypropylene fiber. It has good infiltration effect, and its mutually soluble flax fibers can enter the lumen and microfibers of the polypropylene fiber, forming a network anchor and bonding effect inside the polypropylene fiber, and forming a package outside the polypropylene fiber, creating a triple force. With a strong link structure, the composite material has high bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance.

In some embodiments, in terms of parts by mass, the modified flax fiber in the components of the composite material can specifically be 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, or 46 parts , 48 parts, 50 parts, etc. It can also be other values within the range. It can be selected according to actual needs and is not limited here. The flax fiber in the modified flax fiber has a natural spindle structure and unique pectin bevel holes. The resulting excellent low density and other characteristics can make the composite material have both overall density when used in composite materials. It has the advantages of low carbon emissions and low carbon emissions; and the modified flax fiber is flax fiber modified by isomerized terpene resin. This composition allows polypropylene fiber and modified flax fiber to form a three-dimensional fiber with three forces after heating and compounding. Network structure, and thus composite materials have high bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance. If the content of modified flax fiber is too low, the density of the composite material will be too high, making the automobile structure and other products made of composite materials unable to meet the lightweight requirements. At this time, the content of the binding resin in the composite material is too low. The bonding force between modified flax fiber and polypropylene fiber becomes worse; if the content of modified flax fiber is too high, the density of the composite material will be reduced, but at this time the content of polypropylene fiber will also be too low, which will lead to a reduction in the strength of the composite material, thereby reducing the strength of the composite material. Performance degrades.

The polypropylene fibers in the composite material components can specifically be 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, etc., or within the range Other values of can be selected according to actual needs and are not limited here. Polypropylene fiber has excellent properties of both high strength and wear resistance. If the content of polypropylene fiber is too low, that is, the content of modified flax fiber is too high, the density of the composite material will be reduced, but this will lead to a reduction in the strength of the composite material and thus a decrease in performance. ; If the content of polypropylene fiber is too high, the composite material will have good bonding strength, tensile strength, flexural strength, flexural modulus, and impact resistance. However, if the content of modified flax fiber is too low, it will lead to the deterioration of the prepared composite material. Density increases.

In some embodiments, after the modified flax fiber and polypropylene fiber in the above mass proportions are combined, a composite material with high bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance can be obtained. . specific:

The density of the composite material is ≤1.02g/cm ³ . Optional, the density of the composite material can be 1.02g/cm ³ , 1.01g/cm ³ , 0.99g/cm ³ , 0.96g/cm ³ , 0.94g/cm ³ , 0.92g/cm ³ , 0.90g/cm ^3, etc., can also be other values within the range, which can be selected according to actual needs, and are not limited here. The density of the composite material will affect the weight of the final automobile structure. The greater the density of the composite material, the heavier the composite material will be per unit volume. If the density of the composite material is too high, the prepared automobile structure cannot achieve lightweight effect.

The tensile strength of the composite material is ≥29MPa. Optional, the tensile strength of the composite material can be 29MPa, 30MPa, 31MPa, 32MPa, 33MPa, 34MPa, 35MPa, etc. It can also be other values within the range, according to actual needs. Make your choice, no restrictions here. Tensile strength refers to the maximum tensile force that a composite material can withstand after tensile deformation. The greater the tensile strength, the greater the tensile stress that the composite material can withstand. If the tensile strength of the composite material is too small, the composite material will be easily damaged during processing (such as stretch molding) into an automobile structure, and the prepared automobile structure will have poor tensile properties.

The bending strength of the composite material is ≥37MPa. Optional, the bending strength of the composite material can be 37MPa, 38MPa, 40MPa, 42MPa, 45MPa, 46MPa, 48MPa, etc. It can also be other values within the range, which can be selected according to actual needs. , no limitation is made here. Bending strength refers to the maximum stress that a composite material can withstand when it breaks under bending load or reaches a specified bending moment. The greater the bending strength, the greater the bending load force that the composite material can withstand. If the bending strength of the composite material is too low, the hardness of the prepared automobile structure will be low, and it will be prone to damage when the force it withstands is too large.

The flexural modulus of the composite material is ≥1940Mpa. Optional, the flexural modulus of the composite material can be 1940Mpa, 2000MPa, 2500MPa, 3000MPa, 3500MPa, 3600MPa, 3800MPa, etc. It can also be other values within the range, according to actual needs. Make your choice, no restrictions here. Bending modulus refers to the ability of a composite material to resist deformation under bending load. The greater the bending modulus, the more difficult it is for the composite material to deform. If the flexural modulus of the composite material is too low, the hardness of the prepared automobile structure will be low and it will easily deform during use, which will affect the use of the automobile structure.

The notched impact strength of composite materials is ≥5.6kJ/m ² . Optional, the notched impact strength of composite materials can be 5.6kJ/m ² , 6kJ/m ² , 7kJ/m ² , 8kJ/m ² , 10kJ/m ² , 13kJ/m ² , 15kJ/m ² , 20kJ/m ^2, etc., or other values within the range, which can be selected according to actual needs and are not limited here. Notched impact strength refers to the energy absorbed per unit cross-sectional area when a notched composite material breaks or fractures under the action of impact load. The greater the notched impact strength, the lower the brittleness and stronger toughness of the composite material. If the notched impact strength of the composite material is too low, the automobile structure made of the composite material will have defects such as notches during use. At this time, it will easily break or crack when exposed to external forces, which will affect the use of the automobile structure.

The low-temperature impact strength of the composite material at -40°C is ≥4.7kJ/m ² . Optional, the low-temperature impact strength of the composite material can be 4.7kJ/m ² , 4.9kJ/m ² , 5.2kJ/m ² , 5.5 kJ/m ² , 5.8kJ/m ² , 6.4kJ/m ² , 6.9kJ/m ^{2 ,} etc., can also be other values within the range, which can be selected according to actual needs and are not limited here. In the above scheme, the low-temperature impact strength refers to the energy absorbed by the unit cross-sectional area when the composite material breaks or fractures under the action of impact load at low temperature. The greater the low-temperature impact strength, the lower the low-temperature condition, the lower the brittleness and toughness of the composite material. powerful. If the low-temperature impact strength of the composite material is too low, the automobile structure made of the composite material will be prone to breakage or cracking when exposed to external forces when used in an environment with large temperature changes, which will affect the use of the automobile structure.

Preferably, in terms of parts by mass, the composite material of the present application contains 50 parts of modified flax fiber and 50 parts of polypropylene fiber, and the modified flax fiber is flax fiber modified by isomerized terpene resin. It can be understood that the component parameters of the composite material are controlled within the above range, and the density of the obtained composite material is about 0.90g/cm ³ , the tensile strength is ≥30MPa, the flexural modulus is ≥3500MPa, and the notch impact is ≥8kJ/m ² .

In some embodiments, the above-mentioned composite materials with excellent properties can be prepared by the following preparation method. Specifically, the preparation method includes the following steps:

Step S10: Pre-mix 30 to 50 parts of modified flax fiber and 50 to 70 parts of polypropylene fiber in terms of parts by mass to obtain a first mixed material; wherein the modified flax fiber is isomerized terpene resin Modified flax fiber;

Step S20, subject the first mixed material to an opening process, a carding process and an air-laying process to obtain a second mixed material;

In step S30, the second mixed material is subjected to a heating needling process to obtain a composite material with a three-dimensional fiber network structure.

In the above scheme, modified flax fiber is used as the raw material of the composite material. The modified flax fiber is flax fiber modified by isomerized terpene resin, so that when the modified flax fiber and polypropylene fiber are heated and pressurized during the preparation process, The two can form a strong link structure with three forces, which improves the binding force between modified flax fiber and polypropylene fiber. At the same time, the preparation process also adopts a heating acupuncture process. Through the heating acupuncture process, the modified flax fiber and polypropylene fiber can be combined. Polypropylene fibers are interwoven into a more stable and dense three-dimensional fiber network structure, which greatly reduces the voids inside the composite material, thereby enhancing the tensile strength, flexural strength, flexural modulus, and impact resistance of the composite material.

Before step S10, step S100 is also included, the preparation process of modified flax fiber:

The flax fiber is subjected to an opening process, and then the dissolved isomerized terpene resin solution is sprayed on the modified flax fiber, and after standing, the modified flax fiber is obtained. The opening process refers to breaking up large flax fibers that are in groups or blocks into small pieces or bundles, presenting a loose and mixed state, which reduces the size of the fibers that are laterally connected within the flax fibers and creates conditions for the subsequent modification process.

Among them, the mass content of the isomerized terpene resin is 1% to 10% of the mass of the flax fiber. Optionally, the mass content of the isomerized terpene resin can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. can also be other values within the range, which can be selected according to actual needs and are not limited here. It can be understood that if the mass content of the isomerized terpene resin is within the above range, the modified flax fiber with strong binding force of the present application can be obtained.

The standing time is 5min ~ 10min. It is optional. The standing time can be 5min, 6min, 7min, 8min, 9min, 10min, etc. It can also be other values within the range. It can be selected according to actual needs. This is not limited.

In step S10, the premixing process of modified flax fiber and polypropylene fiber is carried out in a needle mixer. The time of the premixing process is 3 min to 5 min. Optional, the time of the premixing process can be 3 min, 3.2min, 3.4min, 3.6min, 3.8min, 4min, 4.2min, 4.4min, 4.6min, 4.8min, 5min, etc. It can also be other values within the range. It can be selected according to actual needs and is not limited here. . If the premixing time is too short, it will be difficult to mix the modified flax fiber and polypropylene fiber evenly, which is not conducive to subsequent processes; if the premixing time is too long, the energy consumption for the preparation of composite materials will increase, thereby increasing the quality of the composite materials. Preparation costs. After mixing in step S10, the first mixed material can be obtained.

In step S20, the first mixed material is first subjected to an opening process. The opening process is performed in an opening machine. Opening refers to breaking the large first mixed material into small pieces into small pieces. Or small bundles, showing a loose mixed state, which reduces the scale of the lateral connections of the fibers in the first mixed material, creating conditions for subsequent further loosening to a single fiber state.

Further, after the opening is completed, the first mixed material is subjected to a carding process, and the carding process is carried out in a mechanical carding machine. After the first mixed raw material is opened by the opening machine, there are still fiber blocks or fiber bundles, and the arrangement of the fibers is relatively disordered. The mechanical carding machine can further loosen the opened fiber aggregates and reduce the fiber as much as possible. The fiber dispersion of the first mixed material is improved without damage, so that the fiber bundles or fiber blocks are relatively completely divided into single fiber states, and the modified flax fiber and polypropylene fiber are further evenly and carefully mixed.

Furthermore, the carded first mixed material is finally subjected to an air-laying process, and the air-laying process is carried out in an air-laying machine. After the first mixed material is carded, use airflow to peel off the restraints from the mechanical carding machine (a peeling method of blowing or suctioning or blowing and sucking together), so that the dispersed single fibers pass through the air duct, and the airflow is diffused after passing through the air duct. , slow down, and then the modified flax fibers and polypropylene fibers in the airflow are arranged in order from beginning to end and become irregular, and are deposited to form a second mixed material (a network of modified flax fibers and polypropylene fibers interwoven).

It should be noted that the density of the air-laid mesh in step S20 can be selected according to actual needs and is not limited here. Preferably, the density of the air laid mesh is 2000g/m ² .

Acupuncture process, modified flax fiber and polypropylene fiber winding forming process, modified flax fiber soaking polypropylene fiber process, melted modified flax fiber bonding polypropylene fiber to form the third mixed material process, the third mixed material winding and weaving solidification process . specific:

The acupuncture process refers to: using a needle with side teeth to drive the fibers on the surface of the geothermal mixed material to penetrate into the interior of the second mixed material, and repeatedly acupuncture back and forth, so that the modified flax fibers and polypropylene fibers are entangled with each other.

The winding forming process of modified flax fiber and polypropylene fiber means that the second mixed material after needling is continuously wound on the mold to facilitate subsequent processing.

The process of infiltrating modified flax fiber into polypropylene fiber refers to the process in which the polypropylene fiber wrapped around the modified flax fiber is heated to a molten state, and the isomerized terpene resin adheres to the surface of the polypropylene fiber or penetrates into the interior of the polypropylene fiber.

The molten modified flax fiber binds the polypropylene fiber to form the third mixed material process: the molten isomerized terpene resin serves as a binding phase to connect the modified flax fiber and the polypropylene fiber as a whole to build a three-dimensional fiber network structure. Third mixed material.

The winding and braiding curing process of the third mixed material refers to winding the third mixed material around a mold, and then solidifying it at room temperature or under heating conditions, thereby obtaining the composite material of the present application.

It can be understood that through the above-mentioned steps S100, S10, S20, and S30, the composite material of the present application that is lightweight and has high bonding strength, tensile strength, flexural strength, flexural modulus, and impact resistance can be obtained.

The following is explained in conjunction with specific embodiments:

Example 1:

(1) Put the flax fiber into the opening machine for the opening process, and then put it into the needle mixer to mix. The isomerized terpene resin is dissolved in ethanol for later use. Spray the dissolved isomerized terpene resin while mixing. , in terms of parts by mass, the amount of isomerized terpene resin added is 1% of the flax fiber, mixed for 3 minutes, and left for 5 to 10 minutes to obtain modified flax fiber.

(2) In terms of parts by mass, 30 parts by mass of modified flax fiber and 70 parts by mass of polypropylene fiber are subjected to a premixing process, an opening process, a carding process, an air laying process and a heated needle punching process to obtain a composite material. Among them, the temperature of the needle punching heating process is controlled at 140°C, and the air flow laying area density is 2000g/m ² .

(3) Cut the composite material into a suitable size, put it into an oven and heat it at a temperature of 200°C and a heating time of 5 minutes. Take it out and put it into a 4mm mold and press it into a plate. The pressure is 22MPa. Cut it into national standard specimens and test it. performance.

Example 2:

Different from Example 1, the addition amount of isomerized terpene tree is 5% of the flax fiber, and the flax fiber used is 40 parts by mass, and the polypropylene fiber is 60 parts by mass.

Example 3:

What is different from Example 1 is that the amount of isomerized terpene tree added is 10% of the flax fiber, and the flax fiber used is 50 parts by mass, and the polypropylene fiber is 50 parts by mass.

Example 4:

The difference from Example 1 is that the modified flax fiber is 20 parts by mass and the polypropylene fiber is 80 parts by mass.

Example 5:

The difference from Example 1 is that the modified flax fiber is 60 parts by mass and the polypropylene fiber is 40 parts by mass.

Comparative example 1:

(1) According to parts by weight, 40 parts by weight of flax fiber (unmodified) and 60 parts by weight of polypropylene fiber are obtained through a premixing process, an opening process, a carding process, an air laying process and a heated needle punching process. Composite materials, in which the air-laid area density is 2000g/m ² ;

(2) Cut the composite material into a suitable size, put it into an oven and heat it at a heating temperature of 200°C and a heating time of 5 minutes. Take it out and put it into a 4mm mold and press it into a plate. The pressure is 23MPa and cut into national standard splines. , test performance.

Comparative example 2:

(1) In parts by weight, 20 parts by weight of flax fiber, 20 parts by weight of coconut palm fiber, and 60 parts by weight of polypropylene fiber are processed through the premixing process, the opening process, the carding process, the air-laying process and the heating needle. The composite material is obtained through the stabbing process, in which the air-laid surface density is 2000g/m ² ;

(2) Cut the composite material into a suitable size, put it into an oven and heat it at a heating temperature of 200°C and a heating time of 5 minutes. Take it out and put it into a 4mm mold and press it into a plate. The pressure is 23MPa and cut into national standard splines. , test performance.

Comparative example 3:

(1) Weigh each raw material in proportion, put 70 parts by weight of polypropylene, 30 parts by weight of maleic anhydride-grafted polypropylene, and 10 parts by weight of epoxy resin into the mixer, and then put them into the extruder after mixing. In the process, the extrusion temperature is 180°C ~ 230°C, and the mixed raw materials are passed through a screw extruder, a spinneret, a cooling and a cutting machine to obtain modified polypropylene fiber, which is ready for use.

(2) By weight, 50 parts by weight of flax fiber and 50 parts by weight of polypropylene fiber are mixed, opened, air-laid, needled, soaked in water, extruded for 6 hours, dried for 4 hours, and the mold temperature is 200 ℃ hot press forming 4mm plate, the pressure is 12MPa, cut into national standard standard splines, and test the performance.

Comparative example 4:

By weight, mix 30 parts by weight of 1250 mesh talcum powder, 7 parts by weight of POE8730, and 63 parts by weight of polypropylene K7726, melt and blend through an extruder, and dice to obtain composite material particles. The composite material particles are baked After drying, the national standard sample is obtained through injection molding to test the performance.

Test: The 4mm sample prepared by the methods of the above examples and comparative examples was compared and tested in accordance with national standards such as GB/T1033.1, GB/T1040.1/2, GB/T9341, GB/T1043.1 and other national standards. The data is shown in the table below:

It can be seen from the test results of Examples 1 to 3 that when the components meet the requirements of 30 to 50 parts of modified flax fiber and 50 to 70 parts of polypropylene fiber, and the premixing process, opening process, carding process, and air laying are adopted, The composite material obtained by the mesh process and the heated needling process is lightweight and has high bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance.

It can be seen from the test results of Example 1 and Example 4 that the flax fiber in the modified flax fiber has a natural spindle structure and unique pectin bevel holes, resulting in excellent low density and other properties, which can be used in When used in composite materials, the composite material can have the advantages of low overall density and low carbon emissions; and the modified flax fiber is flax fiber modified by isomerized terpene resin. This composition makes polypropylene fiber and modified Flax fibers can form a three-dimensional fiber network structure with three forces after heating and compounding. The composite material has high bonding strength, tensile strength, flexural strength, flexural modulus and impact resistance. If the content of modified flax fiber is too low, the density of the composite material will be too high, making the automobile structure and other products made of composite materials unable to meet the lightweight requirements. At this time, the content of the binding resin in the composite material is too low. The bonding force between modified flax fiber and polypropylene fiber becomes worse, and thus the performance becomes worse.

It can be seen from the test results of Example 1 and Example 5 that polypropylene fiber has excellent characteristics of both high strength and wear resistance. If the content of polypropylene fiber is too low, that is, the content of modified flax fiber is too high, the density of the composite material will be reduced. , but it will lead to a decrease in the strength of the composite material and thus a decrease in performance.

It can be seen from the test results of Example 2 and Comparative Examples 1 and 2 that when the fiber addition amount is the same, the composite material prepared by the method of the present invention is compared with the composite material simply compounded and added with coconut fiber. Example The tensile strength of 3 increased by 17.5% and 36% respectively, the flexural strength increased by 24.7% and 13.2% respectively, the flexural modulus increased by 27.2% and 57.3% respectively, and the notched impact strength increased by 19.4% and 79.2% respectively. Better performance.

It can be seen from the test results of Example 2 and Comparative Example 3 that when the fiber addition amount is the same, the composite material prepared by the method of the present invention has better impact resistance at normal temperature and low temperature than the composite material modified by epoxy resin in Example 2. Impact performance has been significantly improved, increasing by 16% and 20% respectively.

It can be seen from the test results of Example 1 and Comparative Example 4 that when the fiber or mineral addition amount is the same, the tensile strength of the composite material prepared by the method of the present invention is improved compared with the mineral-filled composite material. 36.6%, the flexural strength increased by 42.3%, the flexural modulus increased by 20.9%, and the low-temperature notched impact strength increased by 96%.

In summary, it can be seen that the composite material prepared by the present invention has lower density, higher tensile strength, bending strength, flexural modulus, and impact resistance. The performance of the composite material has been greatly improved, has significant effects, and has more High rigidity and toughness. The use of renewable hemp fiber-reinforced polymer materials can not only reduce the use of inorganic mineral powder and petroleum resin polypropylene, reduce the consumption of ore and petroleum resources, but also enhance the strength of the material, which can meet the needs of lightweight and high-performance automotive materials. requirements.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application, but not to limit it. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art will understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some or all of the technical features. . However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of this application.

Claims (10)

1. A composite material, characterized in that the components of the composite material include modified flax fiber and polypropylene fiber, and the modified flax fiber and the polypropylene fiber are constructed into a three-dimensional fiber network structure; Among them, in terms of parts by mass, the modified flax fiber in the composite material is 30 to 50 parts, the polypropylene fiber in the composite material is 50 to 70 parts, and the modified flax fiber is isomerized Terpene resin modified flax fiber. 2. The composite material according to claim 1, characterized in that the composite material has at least one of the following characteristics: (1) The density of the composite material is ≤1.02g/cm ³ ; (2) The tensile strength of the composite material is ≥29MPa; (3) The flexural strength of the composite material is ≥37MPa; (4) The flexural modulus of the composite material is ≥1940Mpa; (5) The notched impact strength of the composite material is ≥5.6kJ/m ² ; (6) The low-temperature impact strength of the composite material at -40°C is ≥4.7kJ/m ² . 3. The composite material according to claim 1, characterized in that the components of the composite material include modified flax fiber and polypropylene fiber, and the modified flax fiber and the polypropylene fiber are constructed into a three-dimensional fiber network structure; Among them, in terms of parts by mass, the modified flax fiber in the composite material is 50 parts, the polypropylene fiber in the composite material is 50 parts, and the modified flax fiber is modified by isomerized terpene resin. Sexy flax fiber. 4. A method for preparing composite materials, characterized in that the preparation method includes the following steps: In terms of parts by mass, 30 to 50 parts of modified flax fiber and 50 to 70 parts of polypropylene fiber are subjected to a premixing process to obtain the first mixed material; wherein the modified flax fiber is modified with isomerized terpene resin. sexual flax fiber; The first mixed material is subjected to an opening process, a carding process and an air-laying process to obtain a second mixed material; The second mixed material is subjected to a heating needling process to obtain a composite material with a three-dimensional fiber network structure. 5. The preparation method according to claim 4, characterized in that the preparation method has at least one of the following characteristics: (1) The fiber length of the polypropylene fiber is 100mm~150mm; (2) The fiber diameter of the polypropylene fiber is 10 μm to 50 μm; (3) The time of the pre-mixing process is 3 to 5 minutes; (4) The temperature of the heating needling process is 140°C to 160°C. 6. The preparation method according to claim 4, characterized in that the heating acupuncture process includes the following steps: The acupuncture process, the winding forming process of the modified flax fiber and the polypropylene fiber, the process of soaking the polypropylene fiber with the modified flax fiber, and the melted modified flax fiber bonding with the polypropylene fiber to form a third mixture Material process, the third mixed material undergoes a winding, braiding and solidification process. 7. The preparation method according to claim 4, characterized in that the preparation method also includes a preparation process of the modified flax fiber: The flax fiber is subjected to an opening process, and then the dissolved isomerized terpene resin solution is sprayed on the flax fiber, and after standing, the modified flax fiber is obtained. 8. The preparation method according to claim 7, characterized in that, in parts by mass, the mass of the isomerized terpene resin is 1% to 10% of the mass of the flax fiber. 9. The preparation method according to claim 4, characterized in that the isomerized terpene resin is β-pinene, terpene and hydrocarbon compounds or copolymers catalyzed by iodine or zinc at 200 to 260°C. isomer. 10. The preparation method according to claim 4, characterized in that the preparation method has at least one of the following characteristics: (1) The density of the composite material is ≤1.02g/cm ³ ; (2) The tensile strength of the composite material is ≥29MPa; (3) The flexural strength of the composite material is ≥37MPa; (4) The flexural modulus of the composite material is ≥1940Mpa; (5) The notched impact strength of the composite material is ≥5.6kJ/m ² ; (6) The low-temperature impact strength of the composite material at -40°C is ≥4.7kJ/m ² .