Preparation method of para-aramid and natural rubber high interface performance composite material

Abstract

The invention relates to a fiber composite material, and discloses a preparation method of a para-aramid and natural rubber high interface performance composite material, which comprises the following four steps: preparing a chloroform solution of natural rubber, preparing a nano para-aramid-natural rubber composite mixing material, preparing impregnated para-aramid, and mixing and vulcanizing. According to the preparation method, the para-aramid is effectively connected with the matrix through the'bridge 'effect of the para-aramid nanophase by a method for constructing the para-aramid nanophase in the matrix material, so that the interfacial acting force of the para-aramid is enhanced, and the high performance of the para-aramid in the composite material is fully exerted; the problems of poor interfacial compatibility with a base material, low binding force and the like caused by smooth surface and chemical inertness of the para-aramid at present are effectively solved, and the para-aramid nanophase can also remarkably improve the strength and toughness of the base material.

Description

Technical Field

[0001] The present invention relates to fiber composite materials, and particularly to a preparation method of a composite material with high interfacial performance of para-aramid and natural rubber. Background Art

[0002] Poly(p-phenylene terephthalamide) (PPTA) fiber, also known as para-aramid fiber, is a high-performance fiber with large production volume and wide applications. It has the advantages of high strength, high modulus, high temperature resistance, acid and alkali resistance, and light weight, and plays an important role in high-tech fields such as aerospace, national defense industry, rail transit, and new energy. The production of para-aramid fiber has relatively high technical barriers, and together with carbon fiber and polyimide film, they are known as the three bottleneck key polymer materials restricting the development of high-tech industries in China.

[0003] The surface of para-aramid is smooth, and there are problems of poor interfacial compatibility and low bonding force with the matrix. Usually, chemical methods (such as surface etching, surface grafting, etc.) and physical methods (such as surface coating, ultrasonic impregnation, etc.) are used to modify the fiber surface to increase the number of polar groups (such as hydroxyl groups, amino groups) on the fiber surface and the roughness of the fiber surface, thereby enhancing the interfacial bonding force between the fiber and the matrix material. However, while these treatment technologies improve the surface adhesion performance of para-aramid, they will cause varying degrees of damage to the properties of the fiber itself, and the preparation process is relatively complex, mostly for small-batch experimental treatment. For large-scale industrial production and the durability of the fiber surface modification effect, etc., further research is still needed. Summary of the Invention

[0004] To solve the above problems, the present invention proposes a method of introducing a third phase - nano-phase between the fiber and the matrix material to enhance the interfacial interaction between para-aramid and the matrix. The nano-phase can effectively connect the matrix polymer and para-aramid as a "bridge". On the one hand, the nano-phase can increase the roughness of the fiber surface, thereby improving the mechanical interlocking ability with the matrix; on the other hand, the nano-phase can also act as a functional gradient interface to effectively reduce the degree of stress concentration. Considering the compatibility with the matrix polymer, the nano-phase introduced in this method is preferably an organic phase. However, the properties of ordinary polymers are quite different from those of para-aramid, and they cannot effectively interact with the surface of para-aramid. Therefore, para-aramid nano-phase with the same composition as para-aramid becomes the best choice.

[0005] The present invention adopts the low-temperature solution polycondensation method. In the natural rubber solution, the steric effect of rubber macromolecules is utilized to reduce the probability of hydrogen bond formation between para-aramid molecular chains, thereby weakening the aggregation degree between para-aramid molecular chains and regulating their molecular weight, and directly synthesizing nano para-aramid from monomers (p-phenylenediamine and terephthaloyl chloride) in one step. Subsequently, the para-aramid fiber is impregnated therein, so that the para-aramid interacts with the para-aramid fiber through hydrogen bonds, π-π stacking between benzene rings, etc., thereby constructing a para-aramid nano-phase on the fiber surface. In addition, the para-aramid nano-phase is generated in-situ in the rubber matrix and has good compatibility with the matrix. Experiments show that the construction of the para-aramid nano-phase can significantly improve the interfacial force between the para-aramid fiber filament (or cloth) and natural rubber; and the nano para-aramid dispersed in the natural rubber matrix can simultaneously improve various mechanical properties of natural rubber such as strength and toughness, thereby realizing the double improvement of the composite rubber interface and matrix properties.

[0006] The preparation method of the composite material with high interfacial performance of para-aramid and natural rubber of the present invention includes the following steps: 1) Under heating conditions, natural rubber is added to chloroform and stirred until completely dissolved. It is evenly divided into two parts. p-Phenylenediamine (PPD) and lithium chloride (LiCl) are added to the first part, and terephthaloyl chloride (TPC) is added to the second part. It is placed in an ice-water bath under nitrogen protection, and the second part is gradually dropped into the first part and reacted at room temperature for 2 h; 2) The reaction solution in step 1) is filtered, washed with water until neutral, and then dried to obtain a nano para-aramid-natural rubber composite masterbatch; 3) The para-aramid product is washed with boiling acetone and ethanol respectively, then washed with water, vacuum dried, and added to the reaction solution in step 1) for impregnation. After taking out, it is rinsed with ethanol and then vacuum dried to obtain the impregnated para-aramid for standby; 4) 100 parts by weight of the nano para-aramid-natural rubber composite masterbatch obtained in step 2) is mixed with the following parts by weight of substances: 40-60 parts of accelerator, 5-25 parts of the impregnated para-aramid obtained in step 3), 2-8 parts of activator, 0.5-2 parts of vulcanizing agent, and 0.5-1.5 parts of auxiliary agent. After mixing evenly, it is vulcanized under high temperature and high pressure to obtain the composite material with high interfacial performance of para-aramid and natural rubber.

[0007] Specifically, in step 1), the dosage ratio of natural rubber to chloroform is (1-5) g / 100 mL; the dosage of p-phenylenediamine is 40%-80% of the weight of the natural rubber, the dosage of lithium chloride is 20%-60% of the weight of the natural rubber; the dosage of terephthaloyl chloride is 20%-60% of the weight of the natural rubber. In step 3), the para-aramid product is a fiber bundle or cloth. In step 4), the vulcanization temperature is 120°C-150°C, the vulcanization pressure is 8-12 MPa, and the vulcanization time is 10-20 min; the accelerator is one or a combination of more of accelerator N330, zinc oxide, 2-mercaptobenzothiazole, diphenylguanidine, and accelerator DM; the activator is one or a combination of more of stearic acid, rubber activator 420, rubber activator 450, or rubber activator 480; the vulcanizing agent is sulfur; the auxiliary agent is one or a combination of more of antioxidant 4020, bromonaphthalene mildew preventive, or 2-hydroxybenzotrione ultraviolet absorber.

[0008] Different from the existing para-aramid composite materials, the present invention constructs para-aramid nano-phases in the natural rubber material and uses them to coat the surface of para-aramid. At the same time, as a reinforcing material, it is directly and fully mixed with natural rubber, which doubles the improvement of the connection between the matrix and para-aramid, and effectively solves the problems such as the smooth surface of para-aramid and poor interfacial adhesion. By constructing para-aramid nano-phases in the matrix material, the present invention effectively connects para-aramid with the matrix through the "bridge" effect of para-aramid nano-phases, thereby enhancing the interfacial force, enabling the high performance of para-aramid in the composite material to be fully exerted, and effectively solving the problems such as poor interfacial compatibility and low bonding force between para-aramid and the matrix material caused by the smooth surface and chemical inertness of para-aramid. In addition to the "bridge" effect, para-aramid nano-phases can also significantly improve the strength and toughness of the matrix material. Description of the Drawings

[0009] Figure 1 SEM diagrams of para-aramid raw filaments for Comparative Example 1 (D1), impregnated para-aramid filaments for Example 1 (S1), and impregnated para-aramid cloth for Example 2 (S2). Detailed Embodiments

[0010] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0011] Example 1 A preparation method of a para-aramid and natural rubber high-interfacial performance composite material includes the following steps: (1) At 40 °C, 1 g of NR was dissolved in a three-necked flask containing 50 ml of CHCl3 solution and stirred at 600 rmp until completely dissolved. Then the solution was divided into two parts. One part was added with 0.32 g of PPD and 0.25 g of LiCl, and the other part was added with 0.6 g of TPC. Under nitrogen protection and 0 °C ice-water bath conditions, the TPC / NR solution was slowly added dropwise into the PPD / NR solution using a constant-pressure dropping funnel. After the entire system was added dropwise, it was transferred to room temperature and reacted for another 2 h to obtain a nano-PPTA / NR solution. At the same time, a portion of the nano-PPTA / NR solution was washed with deionized water until neutral and dried for 24 h to obtain a nano-PPTA / NR composite masterbatch. (2) The para-aramid fiber was washed with boiling acetone and ethanol for 1 h respectively, washed with deionized water and dried in a vacuum drying oven at 60 °C until dry. The nano-PPTA / NR solution obtained in step (1) was evenly poured into a 500 ml beaker, and the dried para-aramid fiber was placed in the beaker and impregnated for 5 min. After taking it out, it was immediately rinsed with ethanol and placed in a vacuum at 80 °C for 12 h and then taken out for standby to obtain the impregnated para-aramid fiber. (3) 100 parts by weight of the nano-PPTA / NR composite masterbatch obtained in step (1) was mixed with the following parts by weight of substances: 20 parts of N330 accelerator, 20 parts of 2-mercaptobenzothiazole, 10 parts of accelerator DM, 15 parts of the impregnated para-aramid fiber obtained in step (2), 4 parts of stearic acid, 2 parts of rubber activator 420, 1 part of sulfur, 1 part of antioxidant 4020, and 0.5 part of bromonaphthalene mildew preventive. After mixing evenly, it was vulcanized at 130 °C and 10 MPa for 15 min to obtain a para-aramid and natural rubber high-interface performance composite material.

[0012] Example 2 A preparation method of a para-aramid and natural rubber high-interface performance composite material, comprising the following steps: (1) At 40 °C, 1.3 g of NR was dissolved in a three-necked flask containing 50 ml of CHCl3 solution and stirred at 600 rmp until completely dissolved. Then the solution was divided into two parts. One part was added with 0.5 g of PPD and 0.3 g of LiCl, and the other part was added with 0.8 g of TPC. Under nitrogen protection and 0 °C ice-water bath conditions, the TPC / NR solution was slowly added dropwise into the PPD / NR solution using a constant-pressure dropping funnel. After the entire system was added dropwise, it was transferred to room temperature and reacted for another 2 h to obtain a nano-PPTA / NR solution. At the same time, a portion of the nano-PPTA / NR solution was washed with deionized water until neutral and dried for 24 h to obtain a nano-PPTA / NR composite masterbatch. (2) Wash the para-aramid fabric with boiling acetone and ethanol for 1.5 h respectively, wash it with deionized water and dry it in a vacuum drying oven at 80 °C until it is completely dry. Pour the nano-PPTA / NR solution obtained in step (1) evenly into a 500 ml beaker, place the dried para-aramid fabric in the beaker, soak it for 15 min, immediately rinse it with ethanol after taking it out, and take it out after placing it under vacuum conditions at 90 °C for 12 h for standby use to obtain the impregnated para-aramid filaments; (3) Mix 100 parts by weight of the nano-PPTA / NR composite masterbatch obtained in step (1) with the following parts by weight of substances: 20 parts of accelerator N330, 20 parts of accelerator DM, 5 parts of the impregnated para-aramid fabric obtained in step (2), 8 parts of stearic acid, 2 parts of sulfur, and 1 part of antioxidant 4020. After mixing evenly, vulcanize it at 150 °C and 12 MPa for 10 min to obtain the para-aramid and natural rubber high interfacial performance composite material.

[0013] Comparative Example 1 A preparation method of a para-aramid and natural rubber composite material, the operation is as follows: Mix the following parts by weight of substances: 100 parts of natural rubber, 20 parts of accelerator N330, 20 parts of 2-mercaptobenzothiazole, 10 parts of accelerator DM, 15 parts of para-aramid filaments, 4 parts of stearic acid, 2 parts of rubber activator 420, 1 part of sulfur, 1 part of antioxidant 4020, and 0.5 part of brominated naphthalene mildew preventive. After mixing evenly, vulcanize it at 130 °C and 10 MPa for 15 min to obtain the para-aramid and natural rubber composite material.

[0014] Figure 1 SEM diagrams of the para-aramid raw filaments of Comparative Example 1 (D1), the impregnated para-aramid filaments of Example 1 (S1), and the impregnated para-aramid fabric of Example 2 (S2) are shown. It can be seen from the figure that the surface of the para-aramid raw filaments is smooth, and the surface particle size of the para-aramid in the impregnated para-aramid filaments of Example 1 and the impregnated para-aramid fabric of Example 2 increases, which can significantly improve the mechanical properties of the composite material. The mechanical properties of the composite materials obtained in Example 1, Example 2, and Comparative Example 1 were tested, and the interfacial adhesion forces were measured to be 245.3 N, 215.6 N, and 86.7 N respectively, and the elongation at break was measured to be 257.2%, 192.5%, and 92.9% respectively.

[0015] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a composite material with high interfacial performance of para-aramid and natural rubber, characterized in that It includes the following steps: 1) Under heating conditions, add natural rubber into chloroform, stir until completely dissolved, divide it into two equal parts, add p-phenylenediamine and lithium chloride to the first part, add terephthaloyl chloride to the second part, place it in an ice-water bath under nitrogen protection, drop the second part into the first part drop by drop, and react at room temperature for 2 h; 2) Filter and wash the reaction solution obtained in step 1) with water until neutral, and then dry it to obtain a nano para-aramid-natural rubber composite masterbatch; 3) Wash the para-aramid product with boiling acetone and ethanol respectively, then wash it with water, dry it in vacuum, add it to the reaction solution obtained in step 1) for impregnation, take it out, rinse it with ethanol, and then dry it in vacuum to obtain the impregnated para-aramid for standby; 4) Mix 100 parts by weight of the nano para-aramid-natural rubber composite masterbatch obtained in step 2) with the following parts by weight of substances: 40-60 parts of accelerator, 5-25 parts of the impregnated para-aramid obtained in step 3), 2-8 parts of activator, 0.5-2 parts of vulcanizing agent, and 0.5-1.5 parts of auxiliary agent. After mixing evenly, vulcanize it under high temperature and high pressure to obtain the para-aramid and natural rubber high interface performance composite material.

2. The preparation method according to claim 1, wherein In step 1), the dosage ratio of the natural rubber to chloroform is (1-5) g / 100 mL; the dosage of p-phenylenediamine is 40%-80% of the weight of the natural rubber, the dosage of lithium chloride is 20%-60% of the weight of the natural rubber; the dosage of terephthaloyl chloride is 20%-60% of the weight of the natural rubber.

3. The preparation method according to claim 1, wherein In step 3), the para-aramid product is a fiber bundle or cloth.

4. The preparation method according to claim 1, wherein, In step 4), the vulcanization temperature is 120°C-150°C, the vulcanization pressure is 8-12 MPa, and the vulcanization time is 10-20 min.

5. The preparation method according to claim 1, characterized in that, In step 4), the accelerator is one or a combination of more than one of accelerator N330, zinc oxide, 2-mercaptobenzothiazole, diphenylguanidine, and accelerator DM; the activator is one or a combination of more than one of stearic acid, rubber activator 420, rubber activator 450, or rubber activator 480; the vulcanizing agent is sulfur; the auxiliary agent is one or a combination of more than one of antioxidant 4020, bromonaphthalene mildew preventive, or 2-hydroxybenzotrione ultraviolet absorber.

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