Surface modification composition for para-aramid fiber polyurethane resin composite material, surface modification method and surface modified composite material prepared from surface modification composition and surface modification method

Abstract

The invention provides a para-aramid fiber polyurethane resin composite material surface modification composition which comprises the following components in parts by weight: 100 parts of para-aramid fiber, 12 parts of polyurethane, 7.5 parts of chlorosulfonic acid, 2.5 parts of para-aramid nanofiber and 1 part of chitosan. The para-aramid fiber polyurethane resin composite material surface modification composition comprises the following components in parts by weight: 100 parts of para-aramid fiber, 12 parts of polyurethane, 7.5 parts of chlorosulfonic acid, 2.5 parts of para-aramid nanofiber and 1 part of chitosan. The invention also provides a method for surface modification by using the surface modification composition and a para-aramid fiber polyurethane resin surface modified composite material prepared from the surface modification composition. The para-aramid fiber polyurethane resin surface modified composite material obtained by carrying out surface modification treatment on the para-aramid fiber polyurethane resin composite material surface modification composition has a good interface state, excellent mechanical properties and good impact resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber resin composite materials, in particular to the technical field of para-aramid fiber polyurethane resin composite materials, specifically to a para-aramid fiber polyurethane resin composite material surface modification composition, a surface modification method and a surface modified composite material prepared thereby. Background Art

[0002] Para-aramid (PPTA) fiber is widely used in many fields due to its excellent mechanical properties and heat resistance, mainly including aerospace, military equipment, safety protection, automotive industry and civilian industry. It is one of the most important high-performance fiber materials in impact-resistant composite materials. Compared with traditional rigid resin systems, thermoplastic polyurethane resin (TPU) has better strain adaptability and can achieve large plastic deformation under impact loads, thereby effectively delaying crack propagation and dispersing local stress concentration areas. Therefore, para-aramid reinforced thermoplastic composites constructed based on TPU matrix show obvious advantages in impact resistance, penetration resistance and flexible protective structure design, and have broad prospects for engineering applications.

[0003] However, due to the high crystallinity of PPTA fibers and the lack of polar functional groups on their surface, the fiber surface is chemically inert and has poor interfacial adhesion with the polyurethane resin matrix, which directly affects the overall performance of PPTA / TPU composites. Therefore, new methods for surface modification of para-aramid fiber-polyurethane resin composites are sought, which can achieve good interfacial state, excellent mechanical properties, and good impact resistance in the prepared para-aramid fiber-polyurethane resin surface-modified composites, which have very important practical application value.

[0004] Therefore, it is hoped to provide a surface modification method for a para-aramid fiber polyurethane resin composite material, wherein the para-aramid fiber polyurethane resin surface modified composite material prepared by the method has a good interface state, excellent mechanical properties and good impact resistance. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, one object of the present invention is to provide a surface modification composition for a para-aramid fiber polyurethane resin composite material. The surface modified para-aramid fiber polyurethane resin composite material prepared using the composition has a good interface state, excellent mechanical properties and good impact resistance, and is suitable for large-scale promotion and application.

[0006] Another object of the present invention is to provide a method for surface modification of a para-aramid fiber polyurethane resin composite material. The para-aramid fiber polyurethane resin surface modified composite material prepared by this method has a good interface state, excellent mechanical properties and good impact resistance, and is suitable for large-scale promotion and application.

[0007] Another object of the present invention is to provide a para-aramid fiber polyurethane resin surface modified composite material, which has a good interface state, excellent mechanical properties and good impact resistance, and is suitable for large-scale promotion and application.

[0008] To achieve the above objectives, in a first aspect of the present invention, a surface modification composition of a para-aramid fiber and polyurethane resin composite material is provided, comprising para-aramid fiber and polyurethane, wherein the surface modification composition of the para-aramid fiber and polyurethane further comprises chlorosulfonic acid, para-aramid nanofibers and chitosan, wherein:

[0009] 100 parts by weight of the para-aramid fiber, 12 parts by weight of the polyurethane, 7.5 parts by weight of the chlorosulfonic acid, 2.5 parts by weight of the para-aramid nanofiber, and 1 part by weight of the chitosan.

[0010] Preferably, the para-aramid fiber is a para-aramid fiber staple, a para-aramid fiber filament, a para-aramid fiber two-dimensional braid or a para-aramid fiber three-dimensional braid.

[0011] Preferably, the surface modification composition of the para-aramid fiber polyurethane resin composite material further comprises graphene nanoparticles, and the amount of the graphene nanoparticles is 0.8 parts by weight to 2.5 parts by weight.

[0012] In a second aspect of the present invention, a method for surface modification of a para-aramid fiber polyurethane resin composite material is provided, which is characterized by using the above-mentioned para-aramid fiber polyurethane resin composite material surface modification composition and comprising the following steps:

[0013] (1) preparing the chlorosulfonic acid into a chlorosulfonic acid solution;

[0014] (2) The para-aramid nanofiber is used in the form of a para-aramid nanofiber dispersion; the chitosan is prepared into a chitosan solution; the para-aramid nanofiber dispersion and the chitosan solution are mixed to obtain a para-aramid nanofiber-chitosan composite modified solution;

[0015] (3) soaking the para-aramid fiber in the chlorosulfonic acid solution, then transferring the fiber to water for hydrolysis, and then adding the fiber to the para-aramid nanofiber-chitosan composite modification solution for oscillation and immersion to perform fiber modification to obtain modified para-aramid fiber;

[0016] (4) The polyurethane and the modified para-aramid fiber are stacked and cured to obtain a para-aramid fiber polyurethane resin surface modified composite material.

[0017] Preferably, the specific steps of step (1) are: fully dissolving the chlorosulfonic acid in dichloromethane to obtain the chlorosulfonic acid solution.

[0018] Preferably, in step (2), the para-aramid nanofiber dispersion is prepared by the following method: para-aramid chopped fibers, potassium hydroxide and water are added to dimethyl sulfoxide for sufficient dissociation, then solvent replacement is performed with water, and then high-speed shearing and homogenization are performed.

[0019] Preferably, the specific steps of preparing the chitosan into a chitosan solution in step (2) are: fully dissolving the chitosan in an acetic acid aqueous solution to obtain the chitosan solution.

[0020] Preferably, the surface modification composition of the para-aramid fiber polyurethane resin composite material further comprises graphene nanoparticles, wherein the graphene nanoparticles are present in an amount of 0.8 to 2.5 parts by weight. Between step (2) and step (3), the surface modification method of the para-aramid fiber polyurethane resin composite material further comprises:

[0021] (21) preparing the graphene nanoparticles into a graphene nanoparticle dispersion, and uniformly mixing the graphene nanoparticle dispersion and the para-aramid nanofiber-chitosan composite modified solution to obtain a graphene-para-aramid nanofiber-chitosan composite modified solution;

[0022] The p-aramid nanofiber-chitosan composite modified solution in step (3) is replaced by the graphene-p-aramid nanofiber-chitosan composite modified solution.

[0023] More preferably, the specific steps of preparing the graphene nanoparticles into a graphene nanoparticle dispersion in step (21) are: fully dissolving the graphene nanoparticles in an ethanol aqueous solution to obtain the graphene nanoparticle dispersion.

[0024] In a third aspect of the present invention, a para-aramid fiber and polyurethane resin surface-modified composite material is provided, which is characterized in that it is prepared by the above-mentioned surface modification method of the para-aramid fiber and polyurethane resin composite material.

[0025] The beneficial effects of the present invention are mainly:

[0026] 1. The surface modification composition of the para-aramid fiber polyurethane resin composite material of the present invention comprises para-aramid fiber, polyurethane, chlorosulfonic acid, para-aramid nanofiber and chitosan, wherein the composition comprises 100 parts by weight of para-aramid fiber, 12 parts by weight of polyurethane, 7.5 parts by weight of chlorosulfonic acid, 2.5 parts by weight of para-aramid nanofiber and 1 part by weight of chitosan. The surface modified para-aramid fiber polyurethane resin composite material prepared by using the composition has good interface state, excellent mechanical properties and good impact resistance, and is suitable for large-scale promotion and application.

[0027] 2. The surface modification method of the para-aramid fiber polyurethane resin composite material of the present invention adopts the above-mentioned para-aramid fiber polyurethane resin composite material surface modification composition and comprises the following steps: (1) preparing chlorosulfonic acid into a chlorosulfonic acid solution; (2) using the para-aramid nanofiber in the form of a para-aramid nanofiber dispersion; preparing chitosan into a chitosan solution; mixing the para-aramid nanofiber dispersion and the chitosan solution to obtain a para-aramid nanofiber-chitosan composite modification solution; (3) soaking the para-aramid fiber in the chlorosulfonic acid solution, then transferring it to water for hydrolysis treatment, and then adding it to the para-aramid nanofiber-chitosan composite modification solution for oscillation and impregnation to perform fiber modification treatment to obtain modified para-aramid fiber; (4) stacking polyurethane and modified para-aramid fiber and curing and forming them to obtain a para-aramid fiber polyurethane resin surface modified composite material, which has a good interface state, excellent mechanical properties and good impact resistance, and is suitable for large-scale promotion and application.

[0028] 3. The para-aramid fiber polyurethane resin surface modified composite material of the present invention is prepared by the above-mentioned para-aramid fiber polyurethane resin composite material surface modification method, has a good interface state, excellent mechanical properties and good impact resistance, and is suitable for large-scale promotion and application.

[0029] These and other objects, features and advantages of the present invention are fully reflected in the following detailed description and drawings, and can be achieved by the means, devices and their combinations particularly pointed out in the summary of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is an SEM photograph of the fiber surface after the PPTA fiber in Example 1 was modified with a chlorosulfonic acid solution.

[0031] Figure 2 This is a SEM photo of the fiber surface of the PPTA fiber after modification and sulfonation with the G / ANF / CS composite modification solution in Example 4.

[0032] Figure 3It is a curve diagram of the interface performance change of the para-aramid fiber polyurethane resin composite material obtained in Comparative Example 1, Comparative Example 2, and Examples 1 to 4.

[0033] Figure 4 It is a graph showing the change in mechanical properties of the para-aramid fiber polyurethane resin composite materials obtained in Comparative Example 1, Comparative Example 2, and Examples 1 to 4.

[0034] Figure 5 This is a graph showing the interface performance change of the para-aramid fiber polyurethane resin composite material obtained in Comparative Example 1, Example 3, and Examples 5 to 7.

[0035] Figure 6 It is a graph showing the change in mechanical properties of the para-aramid fiber polyurethane resin composite materials obtained in Comparative Example 1, Example 3, and Examples 5 to 7. DETAILED DESCRIPTION

[0036] In response to the problem that PPTA fibers have high crystallinity and lack polar functional groups on their surfaces, resulting in chemical inertness of the fiber surface and poor interfacial adhesion with the polyurethane resin matrix, which directly affects the overall performance of the PPTA / TPU composite material, the inventors have conducted sufficient and extensive research on the fiber surface modification and regulation of para-aramid fiber polyurethane resin composite materials, and thus proposed a surface modification method for para-aramid fiber polyurethane resin composite materials to improve the interfacial compatibility between para-aramid fibers and polyurethane, enhance the mechanical properties and impact resistance of the para-aramid fiber polyurethane resin composite materials, and improve the practical application value of the para-aramid fiber polyurethane resin composite materials. On this basis, the present invention was completed.

[0037] The present invention first provides a surface modification composition of a para-aramid fiber polyurethane resin composite material, comprising para-aramid fiber, polyurethane, chlorosulfonic acid, para-aramid nanofiber and chitosan, wherein:

[0038] 100 parts by weight of the para-aramid fiber, 12 parts by weight of the polyurethane, 7.5 parts by weight of the chlorosulfonic acid, 2.5 parts by weight of the para-aramid nanofiber, and 1 part by weight of the chitosan.

[0039] The para-aramid (PPTA) fiber can be used in any suitable form. Preferably, the para-aramid fiber is used in the form of para-aramid fiber staple (3mm~100mm), para-aramid fiber filament (10μm~12μm), para-aramid fiber two-dimensional braid or para-aramid fiber three-dimensional braid. More preferably, the para-aramid fiber is used in the form of para-aramid fiber plain weave cloth.

[0040] The chlorosulfonic acid can be used in any suitable form. Preferably, the chlorosulfonic acid is used in the form of a chlorosulfonic acid solution.

[0041] The solvent of the chlorosulfonic acid solution can be any suitable solvent, more preferably, the solvent of the chlorosulfonic acid solution is dichloromethane. Chlorosulfonic acid solutions of different concentrations can be prepared as needed by fully stirring and mixing the chlorosulfonic acid and the dichloromethane.

[0042] The para-aramid nanofibers can be used in any suitable form. Preferably, the para-aramid nanofibers are used in the form of a para-aramid nanofiber dispersion.

[0043] The para-aramid nanofiber dispersion can be prepared by any suitable method. More preferably, the para-aramid nanofiber dispersion is prepared by the following method: para-aramid chopped fibers, potassium hydroxide (KOH) and water, such as deionized water, are added to dimethyl sulfoxide (DMSO) for sufficient dissociation, and then solvent replacement is performed with water, followed by high-speed shearing and homogenization.

[0044] The chitosan (CS) can be used in any suitable form. Preferably, the chitosan (CS) is used in the form of a chitosan solution.

[0045] The solvent of the chitosan solution can be any suitable solvent. More preferably, the solvent of the chitosan solution is an acetic acid aqueous solution.

[0046] The mass fraction of acetic acid in the acetic acid aqueous solution can be determined as needed. Furthermore, the acetic acid aqueous solution is an acetic acid aqueous solution with a mass fraction of 1 wt%.

[0047] The surface modification composition of the para-aramid fiber polyurethane resin composite material may also include any other suitable components. Preferably, the surface modification composition of the para-aramid fiber polyurethane resin composite material further includes graphene nanoparticles, and the graphene nanoparticles are 0.8 to 2.5 parts by weight.

[0048] The graphene nanoparticles can be used in any suitable form. Preferably, the graphene nanoparticles are used in the form of a graphene nanoparticle dispersion.

[0049] The solvent of the graphene nanoparticle dispersion liquid can be any suitable solvent. More preferably, the solvent of the graphene nanoparticle dispersion liquid is an ethanol aqueous solution.

[0050] The volume ratio of ethanol to water in the ethanol aqueous solution can be determined as needed. Furthermore, the volume ratio of ethanol to water in the ethanol aqueous solution is 1:1.

[0051] The polyurethane (polyurethane) can be used in any suitable form. Preferably, the polyurethane is used in the form of a polyurethane film (polyurethane thin film).

[0052] The present invention also provides a method for surface modification of a para-aramid fiber polyurethane resin composite material, which uses the above-mentioned para-aramid fiber polyurethane resin composite material surface modification composition and comprises the following steps:

[0053] (1) preparing the chlorosulfonic acid into a chlorosulfonic acid solution;

[0054] (2) The para-aramid nanofiber is used in the form of a para-aramid nanofiber dispersion; the chitosan is prepared into a chitosan solution; the para-aramid nanofiber dispersion and the chitosan solution are mixed to obtain a para-aramid nanofiber-chitosan composite modified solution;

[0055] (3) soaking the para-aramid fiber in the chlorosulfonic acid solution, then transferring the fiber to water for hydrolysis, and then adding the fiber to the para-aramid nanofiber-chitosan composite modification solution for oscillation and immersion to perform fiber modification to obtain modified para-aramid fiber;

[0056] (4) The polyurethane and the modified para-aramid fiber are stacked and cured to obtain a para-aramid fiber polyurethane resin surface modified composite material.

[0057] The step (1) can adopt any appropriate specific steps. Preferably, the specific steps of the step (1) are: fully dissolving the chlorosulfonic acid in dichloromethane to obtain the chlorosulfonic acid solution.

[0058] In the step (2), the para-aramid nanofiber dispersion can be prepared by any suitable method. Preferably, in the step (2), the para-aramid nanofiber dispersion is prepared by the following method: para-aramid chopped fibers, potassium hydroxide and water are added to dimethyl sulfoxide for sufficient dissociation, and then solvent replacement is performed with water, followed by high-speed shearing and homogenization.

[0059] The step (2) of preparing the chitosan into a chitosan solution may adopt any appropriate specific steps. Preferably, the specific steps of preparing the chitosan into a chitosan solution in step (2) are: fully dissolving the chitosan in an acetic acid aqueous solution to obtain the chitosan solution.

[0060] In the step (3), the soaking time and temperature can be determined as needed. Preferably, in the step (3), the soaking time is 5 minutes and the soaking temperature is 0°C.

[0061] In the step (3), the time and temperature of the oscillation immersion can be determined as needed. Preferably, the time of the oscillation immersion is 5 minutes, and the temperature of the oscillation immersion is room temperature.

[0062] In the case where the surface modification composition of the para-aramid fiber polyurethane resin composite material further comprises graphene nanoparticles, between step (2) and step (3), the surface modification method of the para-aramid fiber polyurethane resin composite material further comprises:

[0063] (21) preparing the graphene nanoparticles into a graphene nanoparticle dispersion, and uniformly mixing the graphene nanoparticle dispersion and the para-aramid nanofiber-chitosan composite modified solution to obtain a graphene-para-aramid nanofiber-chitosan composite modified solution;

[0064] The p-aramid nanofiber-chitosan composite modified solution in step (3) is replaced by the graphene-p-aramid nanofiber-chitosan composite modified solution.

[0065] The step (21) of preparing the graphene nanoparticles into a graphene nanoparticle dispersion can adopt any appropriate specific steps. More preferably, the specific steps of preparing the graphene nanoparticles into a graphene nanoparticle dispersion in the step (21) are: fully dissolving the graphene nanoparticles in an ethanol aqueous solution to prepare the graphene nanoparticle dispersion.

[0066] The present invention also provides a para-aramid fiber polyurethane resin surface-modified composite material, which is prepared by the above-mentioned para-aramid fiber polyurethane resin composite material surface modification method.

[0067] In order to more clearly understand the technical content of the present invention, the following examples are specifically described in detail. It should be understood that the specific examples described herein are merely illustrative of the present invention and are not intended to limit the present invention. Unless otherwise stated, the instruments, drugs, reagents, etc. used in the following examples can be obtained by conventional commercial means.

[0068] Example 1

[0069] In an ice-water bath (0°C), 7.5g of chlorosulfonic acid was slowly added dropwise to 5L of dichloromethane and stirred thoroughly to mix evenly to obtain a chlorosulfonic acid solution (concentration of 1.5g / L). Subsequently, 100g of PPTA fiber was immersed in the chlorosulfonic acid solution and reacted at 0°C for 5min. After the reaction, the PPTA fiber was quickly taken out and transferred to deionized water for hydrolysis treatment for 10min, and then rinsed with deionized water several times to thoroughly remove residual reactants and by-products. The washed PPTA fiber was placed in a 90°C air drying oven and dried for 4h to obtain the sulfonated PPTA fiber (S-PPTA).

[0070] 2.5g of para-aramid chopped fibers (5mm), 0.5g of potassium hydroxide (KOH), and 10mL of deionized water were added to 50mL of dimethyl sulfoxide (DMSO). After sealing, the mixture was magnetically stirred at room temperature for 7 days. The system gradually turned clear and transparent dark red, indicating that the para-aramid chopped fibers were fully dissociated to form para-aramid nanofibers (ANF). Subsequently, the solvent was replaced with a large amount of deionized water to completely remove the DMSO. After that, an ANF aqueous dispersion was prepared by high-speed shearing (1800rpm) and homogenization. The ANF concentration was adjusted to 2.5g / L.

[0071] S-PPTA was immersed in ANF aqueous dispersion and shaken for 5 minutes, then repeatedly rinsed with deionized water and dried in a forced air drying oven at 80°C for 4 hours to obtain para-aramid nanofiber-modified sulfonated PPTA fibers (A@S-PPTA).

[0072] A 12g TPU resin film (12g) was alternately laid in a metal mold with a plain weave of sulfonated PPTA fibers modified with para-aramid nanofibers. The mold was then transferred to a flat-bed vulcanizer for hot pressing. The initial pressure was set at 2.5 MPa. When the temperature reached 100°C, the pressure was increased to 5 MPa. After the temperature reached 130°C, the pressure was maintained at this temperature for 40 minutes. The sample was then removed after cooling to 60°C to obtain the fiber-modified PPTA / TPU composite material A@S-PPTA / TPU.

[0073] Example 2

[0074] In an ice water bath (0°C) condition, 7.5 g chlorosulfonic acid was slowly added into 5 L dichloromethane, and stirred well to make it mixed evenly, to obtain a chlorosulfonic acid solution (concentration of 1.5 g / L). Then, 100 g PPTA fiber was immersed in the chlorosulfonic acid solution, and reacted at 0°C for 5 min. After the reaction was completed, the PPTA fiber was quickly taken out, transferred to deionized water for hydrolysis treatment for 10 min, and then washed with deionized water for several times to completely remove the residual reactants and by-products. The washed PPTA fiber was placed in a 90°C air drying oven for drying for 4 h to obtain sulfonated PPTA fiber (S-PPTA).

[0075] 2.5 g of p-aramid short fibers (5 mm), 0.5 g of potassium hydroxide (KOH), and 10 mL of deionized water were added to 50 mL of dimethyl sulfoxide (DMSO), sealed, and magnetically stirred at room temperature for 7 days. The system gradually turned into a clear and transparent dark red color, indicating that the p-aramid short fibers were fully dissociated to form p-aramid nanofibers (ANF). Then, a large amount of deionized water was used for solvent replacement, and after completely removing the DMSO, the ANF water dispersion was prepared by high-speed shearing (1800 rpm) and homogenization treatment, and the ANF concentration was adjusted to 2.5 g / L.

[0076] 1 g of chitosan (CS) was weighed and added to 1 L of 1 wt% acetic acid aqueous solution, and mechanically stirred at room temperature for 2 h until the CS was completely dissolved to form a uniform and transparent chitosan solution. Ultrasonic treatment was performed for 10 min to remove the bubbles in the solution, and a transparent CS solution with a mass fraction of 0.1 wt% was obtained. The ANF water dispersion and the CS solution were mixed in a volume ratio of 1:1, magnetically stirred at room temperature for 30 min, and ultrasonically treated for 5 min to form an ANF / CS composite modified solution.

[0077] The S-PPTA was immersed in the ANF / CS composite modified solution and oscillated for 5 min, then repeatedly washed with deionized water, and placed in a 80°C air drying oven for drying for 4 h to obtain the p-aramid nanofiber / chitosan synergistically modified sulfonated PPTA fiber (AC@S-PPTA).

[0078] The p-aramid nanofiber / chitosan synergistically modified sulfonated PPTA fiber plain weave cloth and TPU resin film (12 g) were alternately laid in a metal mold, and the mold was transferred to a flat vulcanizing machine for hot pressing. The initial pressure was set to 2.5 MPa, and when the temperature rose to 100°C, the pressure was increased to 5 MPa; after the temperature rose to 130°C, the pressure was maintained for 40 min, and the sample was taken out after cooling to 60°C to obtain the PPTA / TPU composite material AC@S-PPTA / TPU composite material after fiber modification treatment.

[0079] Example 3

[0080] In an ice-water bath (0°C), 7.5g of chlorosulfonic acid was slowly added dropwise to 5L of dichloromethane and stirred thoroughly to mix evenly to obtain a chlorosulfonic acid solution (concentration of 1.5g / L). Subsequently, 100g of PPTA fiber was immersed in the chlorosulfonic acid solution and reacted at 0°C for 5min. After the reaction was completed, the PPTA fiber was quickly taken out, transferred to deionized water for hydrolysis treatment for 10min, and then rinsed with deionized water several times to thoroughly remove residual reactants and by-products. The washed PPTA fiber was placed in a 90°C air drying oven and dried for 4h to obtain the sulfonated PPTA fiber (S-PPTA).

[0081] 2.5g of para-aramid chopped fibers (5mm), 0.5g of potassium hydroxide (KOH), and 10mL of deionized water were added to 50mL of dimethyl sulfoxide (DMSO). After sealing, the mixture was magnetically stirred at room temperature for 7 days. The system gradually turned clear and transparent dark red, indicating that the para-aramid chopped fibers were fully dissociated to form para-aramid nanofibers (ANF). Subsequently, the solvent was replaced with a large amount of deionized water to completely remove the DMSO. After that, an ANF aqueous dispersion was prepared by high-speed shearing (1800rpm) and homogenization. The ANF concentration was adjusted to 2.5g / L.

[0082] 1g of chitosan (CS) was weighed and added to 500mL of a 1wt% aqueous acetic acid solution. The mixture was mechanically stirred at room temperature for 2h until the CS was completely dissolved, forming a homogeneous, transparent chitosan solution. Ultrasonic treatment was performed for 10min to remove bubbles from the solution, resulting in a transparent 0.2wt% CS solution. The ANF aqueous dispersion and CS solution were then mixed in a 1:1 ratio (500ml of ANF aqueous dispersion, 1.25g of ANF used). The mixture was magnetically stirred at room temperature for 30min and ultrasonicated for 5min to form an ANF / CS composite modified solution.

[0083] S-PPTA was immersed in the ANF / CS composite modification solution and shaken for 5 minutes, then repeatedly rinsed with deionized water and dried in an 80°C forced air drying oven for 4 hours to obtain para-aramid nanofiber / chitosan synergistically modified sulfonated PPTA fiber (AC@S-PPTA).

[0084] A plain weave of sulfonated PPTA fibers modified with para-aramid nanofibers / chitosan and a 12g TPU resin film were alternately laid in a metal mold. The mold was then transferred to a flat-bed vulcanizer for hot pressing. The initial pressure was set at 2.5 MPa. When the temperature reached 100°C, the pressure was increased to 5 MPa. After the temperature reached 130°C, the pressure was maintained at this temperature for 40 minutes. The sample was then removed after cooling to 60°C to obtain the fiber-modified PPTA / TPU composite, AC@S-PPTA / TPU.

[0085] Example 4

[0086] In an ice-water bath (0°C), 7.5g of chlorosulfonic acid was slowly added dropwise to 5L of dichloromethane and stirred thoroughly to mix evenly to obtain a chlorosulfonic acid solution (concentration of 1.5g / L). Subsequently, 100g of PPTA fiber was immersed in the chlorosulfonic acid solution and reacted at 0°C for 5min. After the reaction, the PPTA fiber was quickly taken out and transferred to deionized water for hydrolysis treatment for 10min, and then rinsed with deionized water several times to thoroughly remove residual reactants and by-products. The washed PPTA fiber was placed in a 90°C air drying oven and dried for 4h to obtain the sulfonated PPTA fiber (S-PPTA).

[0087] 2.5g of para-aramid chopped fibers (5mm), 0.5g of potassium hydroxide (KOH), and 10mL of deionized water were added to 50mL of dimethyl sulfoxide (DMSO). After sealing, the mixture was magnetically stirred at room temperature for 7 days. The system gradually turned clear and transparent dark red, indicating that the para-aramid chopped fibers were fully dissociated to form para-aramid nanofibers (ANF). Subsequently, the solvent was replaced with a large amount of deionized water to completely remove the DMSO. After that, an ANF aqueous dispersion was prepared by high-speed shearing (1800rpm) and homogenization. The ANF concentration was adjusted to 2.5g / L.

[0088] 1g of chitosan (CS) was weighed and added to 333mL of a 1wt% aqueous acetic acid solution. Mechanical stirring was performed at room temperature for 2h until the CS was completely dissolved, forming a homogeneous, transparent chitosan solution. Ultrasonic treatment was performed for 10min to remove bubbles from the solution, resulting in a transparent 0.3wt% CS solution. The ANF aqueous dispersion and CS solution were then mixed in a 1:1 ratio (333ml of ANF aqueous dispersion, 0.83g of ANF). The mixture was magnetically stirred at room temperature for 30min and ultrasonicated for 5min to form an ANF / CS composite modified solution.

[0089] S-PPTA was immersed in the ANF / CS composite modification solution and shaken for 5 minutes, then repeatedly rinsed with deionized water and dried in an 80°C forced air drying oven for 4 hours to obtain para-aramid nanofiber / chitosan synergistically modified sulfonated PPTA fiber (AC@S-PPTA).

[0090] A plain weave of sulfonated PPTA fibers modified with para-aramid nanofibers / chitosan and a 12g TPU resin film were alternately laid in a metal mold. The mold was then transferred to a flat-bed vulcanizer for hot pressing. The initial pressure was set at 2.5 MPa. When the temperature reached 100°C, the pressure was increased to 5 MPa. After the temperature reached 130°C, the pressure was maintained at this temperature for 40 minutes. The sample was then removed after cooling to 60°C to obtain the fiber-modified PPTA / TPU composite, AC@S-PPTA / TPU.

[0091] Example 5

[0092] In an ice-water bath (0°C), 7.5g of chlorosulfonic acid was slowly added dropwise to 5L of dichloromethane and stirred thoroughly to mix evenly to obtain a chlorosulfonic acid solution (concentration of 1.5g / L). Subsequently, 100g of PPTA fiber was immersed in the chlorosulfonic acid solution and reacted at 0°C for 5min. After the reaction, the PPTA fiber was quickly taken out and transferred to deionized water for hydrolysis treatment for 10min, and then rinsed with deionized water several times to thoroughly remove residual reactants and by-products. The washed PPTA fiber was placed in a 90°C air drying oven and dried for 4h to obtain the sulfonated PPTA fiber (S-PPTA).

[0093] 2.5g of para-aramid chopped fibers (5mm), 0.5g of potassium hydroxide (KOH), and 10mL of deionized water were added to 50mL of dimethyl sulfoxide (DMSO). After sealing, the mixture was magnetically stirred at room temperature for 7 days. The system gradually turned clear and transparent dark red, indicating that the para-aramid chopped fibers were fully dissociated to form para-aramid nanofibers (ANF). Subsequently, the solvent was replaced with a large amount of deionized water to completely remove the DMSO. After that, an ANF aqueous dispersion was prepared by high-speed shearing (1800rpm) and homogenization. The ANF concentration was adjusted to 2.5g / L.

[0094] 1g of chitosan (CS) was weighed and added to 500mL of a 1wt% aqueous acetic acid solution. The mixture was mechanically stirred at room temperature for 2h until the CS was completely dissolved, forming a homogeneous, transparent chitosan solution. Ultrasonic treatment was performed for 10min to remove bubbles from the solution, resulting in a transparent 0.2wt% CS solution. The ANF aqueous dispersion and CS solution were then mixed in a 1:1 ratio (500ml of ANF aqueous dispersion, 1.25g of ANF used). The mixture was magnetically stirred at room temperature for 30min and ultrasonicated for 5min to form an ANF / CS composite modified solution.

[0095] 2.5 g of graphene (G) nanopowder was weighed and dissolved in 500 mL of a 1:1 ethanol / deionized water mixture. The mixture was sonicated for 30 minutes to obtain a graphene nanoparticle dispersion. The graphene nanoparticle dispersion was then slowly added dropwise to the ANF / CS composite modified solution (1:2 volume ratio) at room temperature with magnetic stirring for 30 minutes. The solution was then sonicated for another 10 minutes to obtain a stable G / ANF / CS composite modified solution.

[0096] S-PPTA was immersed in the G / ANF / CS composite modification solution and shaken for 5 minutes, then repeatedly rinsed with deionized water and dried in an 80°C forced air drying oven for 4 hours to obtain graphene / para-aramid nanofiber / chitosan synergistically modified sulfonated PPTA fibers (GAC@S-PPTA).

[0097] A 12g TPU resin film (12g) and a graphene / para-aramid nanofiber / chitosan-synergistically modified sulfonated PPTA plain weave fabric were alternately laid in a metal mold. The mold was then transferred to a flat-bed vulcanizer for hot pressing. The initial pressure was set at 2.5 MPa. When the temperature reached 100°C, the pressure was increased to 5 MPa. After the temperature reached 130°C, the pressure was maintained at this temperature for 40 minutes. After cooling to 60°C, the sample was removed to obtain the fiber-modified PPTA / TPU composite (GAC@S-PPTA / TPU composite).

[0098] Example 6

[0099] In an ice-water bath (0°C), 7.5g of chlorosulfonic acid was slowly added dropwise to 5L of dichloromethane and stirred thoroughly to mix evenly to obtain a chlorosulfonic acid solution (concentration of 1.5g / L). Subsequently, 100g of PPTA fiber was immersed in the chlorosulfonic acid solution and reacted at 0°C for 5min. After the reaction, the PPTA fiber was quickly taken out and transferred to deionized water for hydrolysis treatment for 10min, and then rinsed with deionized water several times to thoroughly remove residual reactants and by-products. The washed PPTA fiber was placed in a 90°C air drying oven and dried for 4h to obtain the sulfonated PPTA fiber (S-PPTA).

[0100] 2.5g of para-aramid chopped fibers (5mm), 0.5g of potassium hydroxide (KOH), and 10mL of deionized water were added to 50mL of dimethyl sulfoxide (DMSO). After sealing, the mixture was magnetically stirred at room temperature for 7 days. The system gradually turned clear and transparent dark red, indicating that the para-aramid chopped fibers were fully dissociated to form para-aramid nanofibers (ANF). Subsequently, the solvent was replaced with a large amount of deionized water to completely remove the DMSO. After that, an ANF aqueous dispersion was prepared by high-speed shearing (1800rpm) and homogenization. The ANF concentration was adjusted to 2.5g / L.

[0101] 1g of chitosan (CS) was weighed and added to 500mL of a 1wt% aqueous acetic acid solution. The mixture was mechanically stirred at room temperature for 2h until the CS was completely dissolved, forming a homogeneous, transparent chitosan solution. Ultrasonic treatment was performed for 10min to remove bubbles from the solution, resulting in a transparent 0.2wt% CS solution. The ANF aqueous dispersion and CS solution were then mixed in a 1:1 ratio (500ml of ANF aqueous dispersion, 1.25g of ANF used). The mixture was magnetically stirred at room temperature for 30min and ultrasonicated for 5min to form an ANF / CS composite modified solution.

[0102] 2.5 g of graphene (G) nanopowder was weighed and dissolved in 1 L of a 1:1 (volume ratio) ethanol / deionized water mixture. Ultrasonic treatment was performed for 30 minutes to obtain a graphene nanoparticle dispersion. The graphene nanoparticle dispersion was then slowly added dropwise to the ANF / CS composite modified solution (volume ratio 2:2) with magnetic stirring at room temperature for 30 minutes. Ultrasonic treatment was continued for 10 minutes to obtain a stable G / ANF / CS composite modified solution.

[0103] S-PPTA was immersed in the G / ANF / CS composite modification solution and shaken for 5 minutes, then repeatedly rinsed with deionized water and dried in an 80°C forced air drying oven for 4 hours to obtain graphene / para-aramid nanofiber / chitosan synergistically modified sulfonated PPTA fibers (GAC@S-PPTA).

[0104] A 12g TPU resin film (12g) and a graphene / para-aramid nanofiber / chitosan-synergistically modified sulfonated PPTA plain weave fabric were alternately laid in a metal mold. The mold was then transferred to a flat-bed vulcanizer for hot pressing. The initial pressure was set at 2.5 MPa. When the temperature reached 100°C, the pressure was increased to 5 MPa. After the temperature reached 130°C, the pressure was maintained at this temperature for 40 minutes. After cooling to 60°C, the sample was removed to obtain the fiber-modified PPTA / TPU composite (GAC@S-PPTA / TPU composite).

[0105] Example 7

[0106] In an ice-water bath (0°C), 7.5g of chlorosulfonic acid was slowly added dropwise to 5L of dichloromethane and stirred thoroughly to mix evenly to obtain a chlorosulfonic acid solution (concentration of 1.5g / L). Subsequently, 100g of PPTA fiber was immersed in the chlorosulfonic acid solution and reacted at 0°C for 5min. After the reaction, the PPTA fiber was quickly taken out and transferred to deionized water for hydrolysis treatment for 10min, and then rinsed with deionized water several times to thoroughly remove residual reactants and by-products. The washed PPTA fiber was placed in a 90°C air drying oven and dried for 4h to obtain the sulfonated PPTA fiber (S-PPTA).

[0107] 2.5g of para-aramid chopped fibers (5mm), 0.5g of potassium hydroxide (KOH), and 10mL of deionized water were added to 50mL of dimethyl sulfoxide (DMSO). After sealing, the mixture was magnetically stirred at room temperature for 7 days. The system gradually turned clear and transparent dark red, indicating that the para-aramid chopped fibers were fully dissociated to form para-aramid nanofibers (ANF). Subsequently, the solvent was replaced with a large amount of deionized water to completely remove the DMSO. After that, an ANF aqueous dispersion was prepared by high-speed shearing (1800rpm) and homogenization. The ANF concentration was adjusted to 2.5g / L.

[0108] 1g of chitosan (CS) was weighed and added to 500mL of a 1wt% aqueous acetic acid solution. The mixture was mechanically stirred at room temperature for 2h until the CS was completely dissolved, forming a homogeneous, transparent chitosan solution. Ultrasonic treatment was performed for 10min to remove bubbles from the solution, resulting in a transparent 0.2wt% CS solution. The ANF aqueous dispersion and CS solution were then mixed in a 1:1 ratio (500ml of ANF aqueous dispersion, 1.25g of ANF used). The mixture was magnetically stirred at room temperature for 30min and ultrasonicated for 5min to form an ANF / CS composite modified solution.

[0109] 2.5 g of graphene (G) nanopowder was weighed and dissolved in 1.5 L of a 1:1 ethanol / deionized water mixture. Ultrasonic treatment was performed for 30 minutes to obtain a graphene nanoparticle dispersion. Subsequently, the graphene nanoparticle dispersion was slowly added dropwise to the ANF / CS composite modified solution (3:2 volume ratio) at room temperature with magnetic stirring for 30 minutes. Ultrasonic treatment was continued for 10 minutes to obtain a stable G / ANF / CS composite modified solution.

[0110] S-PPTA was immersed in the G / ANF / CS composite modification solution and shaken for 5 minutes, then repeatedly rinsed with deionized water and dried in an 80°C forced air drying oven for 4 hours to obtain graphene / para-aramid nanofiber / chitosan synergistically modified sulfonated PPTA fibers (GAC@S-PPTA).

[0111] A 12g TPU resin film (12g) and a graphene / para-aramid nanofiber / chitosan-synergistically modified sulfonated PPTA plain weave fabric were alternately laid in a metal mold. The mold was then transferred to a flat-bed vulcanizer for hot pressing. The initial pressure was set at 2.5 MPa. When the temperature reached 100°C, the pressure was increased to 5 MPa. After the temperature reached 130°C, the pressure was maintained at this temperature for 40 minutes. After cooling to 60°C, the sample was removed to obtain the fiber-modified PPTA / TPU composite (GAC@S-PPTA / TPU composite).

[0112] Comparative Example 1

[0113] 100g of PPTA fiber plain weave cloth and 12g of TPU resin film were alternately laid in a metal mold. The mold was then transferred to a flat-bed vulcanizer for hot pressing. The initial pressure was set at 2.5MPa. When the temperature reached 100°C, the pressure was increased to 5MPa. After the temperature reached 130°C, the pressure was maintained at this temperature for 40 minutes. After cooling to 60°C, the sample was removed to obtain an unmodified PPTA / TPU composite.

[0114] Comparative Example 2

[0115] In an ice-water bath (0°C), 7.5g of chlorosulfonic acid was slowly added dropwise to 5L of dichloromethane and stirred thoroughly to mix evenly to obtain a chlorosulfonic acid solution (concentration of 1.5g / L). Subsequently, 100g of PPTA fiber was immersed in the chlorosulfonic acid solution and reacted at 0°C for 5min. After the reaction was completed, the PPTA fiber was quickly taken out, transferred to deionized water for hydrolysis treatment for 10min, and then rinsed with deionized water several times to thoroughly remove residual reactants and by-products. The washed PPTA fiber was placed in a 90°C air drying oven and dried for 4h to obtain the sulfonated PPTA fiber (S-PPTA).

[0116] Sulfonated PPTA fiber plain weave and TPU resin film (12g) were alternately laid in a metal mold, and the mold was transferred to a flat-bed vulcanizer for hot pressing. The initial pressure was set at 2.5MPa. When the temperature rose to 100°C, the pressure was increased to 5MPa. After the temperature reached 130°C, the heat and pressure were maintained for 40 minutes. After cooling to 60°C, the sample was removed to obtain the fiber-modified PPTA / TPU composite (S-PPTA / TPU composite).

[0117] Table 1. Amount of raw materials used in comparative examples and examples

[0118]

[0119]

[0120] Example 8 Performance Test

[0121] The para-aramid fiber-polyurethane resin composites obtained in Examples 1 to 7 and Comparative Examples 1 and 2 were tested for peel strength, interlaminar shear strength, tensile strength, flexural strength, and low-velocity impact toughness. The test results are shown in the following table. Peel strength was measured in accordance with GB / T 2791-1995, "Adhesives - T-Peel Strength Test Method - Flexible Material to Flexible Material," interlaminar shear strength was measured in accordance with ASTM D2344, tensile strength was measured in accordance with GB / T 1040-2006, flexural strength was measured in accordance with GB / T 1449-2005, and low-velocity impact toughness was measured in accordance with GB / T 1043-2008.

[0122]

[0123] As shown in the table above, the peel strength, interlaminar shear strength, tensile strength, flexural strength and low-speed impact toughness of the para-aramid fiber polyurethane resin composite material (Comparative Example 1) prepared by compositely preparing PPTA fiber without surface modification and polyurethane all showed low values; the various properties of the para-aramid fiber polyurethane resin composite material (Comparative Example 2) prepared by compositely preparing the PPTA fiber with polyurethane after surface modification treatment with chlorosulfonic acid solution for 5 minutes were improved compared with Comparative Example 1; the peel strength, interlaminar shear strength, tensile strength, flexural strength and low-speed impact toughness of the para-aramid fiber polyurethane resin composite material (Example 1) prepared by compositely preparing the PPTA fiber treated with chlorosulfonic acid solution and then with para-aramid nanofiber and polyurethane continued to improve; after first being treated with chlorosulfonic acid solution, the PPTA fiber (Example 2, Example 3, Example 4) was treated with an ANF / CS composite modification solution composed of para-aramid nanofiber and chitosan (CS mass fractions were 0.1wt%, 0.2wt%, and 0.3wt%, respectively). It can be seen that in CS When the mass fraction is 0.2wt%, the peel strength, interlaminar shear strength, tensile strength, flexural strength and low-speed impact toughness of the composite material (Example 3) thereof and polyurethane all show the maximum value, and the overall performance of the composite material is optimal, indicating that chitosan can significantly improve the performance of the modified composite material; on this basis, Examples 5, 6 and 7 use the same amount of graphene, ANF and CS, but use different volume ratios of graphene solution and ANF / CS composite modified solution (the volume ratio of ANF / CS composite modified solution to graphene solution is (2:1, 2:2, 2:3) G / ANF / CS composite modified solution to treat PPTA fiber, and the obtained para-aramid fiber polyurethane resin composite material has the following characteristics: peel strength, interlaminar shear strength, tensile strength and low-speed impact toughness all show a trend of first increasing and then decreasing, and reaches the optimal value when all modified treatments are performed in Example 6, but the bending performance decreases as a whole, indicating that graphene, as a high modulus rigid reinforcement, is easy to cause local rigidification and microstructural inhomogeneity of the coating when doped, thereby weakening the strain adaptability of the coating. Combined with the accompanying drawings, Figure 1 The SEM photos of the fiber surface when PPTA fiber was modified with chlorosulfonic acid for 5 minutes and Figure 2 From the comparison of SEM photos of the fiber surface when the sulfonated PPTA fiber was treated with G / ANF / CS composite modification solution, it can be seen that the sulfonation treatment increases the grooves and stripes on the fiber surface and increases the roughness of the fiber surface; the surface of the sulfonated PPTA fiber treated with G / ANF / CS composite modification solution shows a dense and uniform interface coating structure, which is beneficial to the optimization and improvement of the interface performance and mechanical properties of the composite material.

[0124] Therefore, the present invention provides a para-aramid fiber polyurethane resin composite surface modification composition, which is used to carry out surface modification treatment of a para-aramid fiber polyurethane resin composite material to prepare a para-aramid fiber polyurethane resin surface modified composite material. The para-aramid fiber polyurethane resin surface modified composite material has a good interface state, excellent mechanical properties and good impact resistance, and the surface modification treatment equipment requirements are low, the operation is simple, the cost is low, and it is suitable for large-scale promotion and application in engineering.

[0125] In summary, the para-aramid fiber polyurethane resin surface modified composite material obtained by surface modification treatment using the para-aramid fiber polyurethane resin composite material surface modification composition of the present invention has a good interface state, excellent mechanical properties and good impact resistance, and is suitable for large-scale promotion and application.

[0126] It can be seen that the objectives of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and illustrated in the embodiments. The embodiments may be modified as desired without departing from the principles described. Therefore, the present invention includes all variations within the spirit and scope of the claims.

Claims

1. A surface modification composition of a para-aramid fiber polyurethane resin composite material, comprising para-aramid fiber and polyurethane, characterized in that: The surface modification composition of the para-aramid fiber polyurethane resin composite material further comprises chlorosulfonic acid, para-aramid nanofibers and chitosan, wherein: 100 parts by weight of the para-aramid fiber, 12 parts by weight of the polyurethane, 7.5 parts by weight of the chlorosulfonic acid, 2.5 parts by weight of the para-aramid nanofiber, and 1 part by weight of the chitosan.

2. The surface modification composition of the para-aramid fiber polyurethane resin composite material according to claim 1, characterized in that: The para-aramid fiber is a para-aramid fiber staple, a para-aramid fiber filament, a para-aramid fiber two-dimensional braid or a para-aramid fiber three-dimensional braid.

3. The surface modification composition of the para-aramid fiber polyurethane resin composite material according to claim 1, characterized in that: The surface modification composition of the para-aramid fiber polyurethane resin composite material further comprises graphene nanoparticles, and the amount of the graphene nanoparticles is 0.8 to 2.5 parts by weight.

4. A surface modification method for a para-aramid fiber polyurethane resin composite material, characterized in that: The surface modification composition of the para-aramid fiber polyurethane resin composite material according to claim 1 is used and includes the following steps: (1) preparing the chlorosulfonic acid into a chlorosulfonic acid solution; (2) The para-aramid nanofiber is used in the form of a para-aramid nanofiber dispersion; the chitosan is prepared into a chitosan solution; the para-aramid nanofiber dispersion and the chitosan solution are mixed to obtain a para-aramid nanofiber-chitosan composite modified solution; (3) soaking the para-aramid fiber in the chlorosulfonic acid solution, then transferring the fiber to water for hydrolysis, and then adding the fiber to the para-aramid nanofiber-chitosan composite modification solution for oscillation and immersion to perform fiber modification to obtain modified para-aramid fiber; (4) The polyurethane and the modified para-aramid fiber are stacked and cured to obtain a para-aramid fiber polyurethane resin surface modified composite material.

5. The surface modification method of the para-aramid fiber polyurethane resin composite material according to claim 4, characterized in that: The specific steps of step (1) are: fully dissolving the chlorosulfonic acid in dichloromethane to obtain the chlorosulfonic acid solution.

6. The surface modification method of the para-aramid fiber polyurethane resin composite material according to claim 4, characterized in that: In the step (2), the para-aramid nanofiber dispersion is prepared by the following method: para-aramid short fibers, potassium hydroxide and water are added to dimethyl sulfoxide for sufficient dissociation, and then solvent replacement is performed with water, followed by high-speed shearing and homogenization.

7. The surface modification method of the para-aramid fiber polyurethane resin composite material according to claim 4, characterized in that: The specific steps of preparing the chitosan into a chitosan solution in step (2) are: fully dissolving the chitosan in an acetic acid aqueous solution to obtain the chitosan solution.

8. The surface modification method of the para-aramid fiber polyurethane resin composite material according to claim 4, characterized in that: The surface modification composition of the para-aramid fiber polyurethane resin composite material further comprises graphene nanoparticles, wherein the graphene nanoparticles are present in an amount of 0.8 to 2.5 parts by weight. Between step (2) and step (3), the surface modification method of the para-aramid fiber polyurethane resin composite material further comprises: (21) preparing the graphene nanoparticles into a graphene nanoparticle dispersion, and uniformly mixing the graphene nanoparticle dispersion and the para-aramid nanofiber-chitosan composite modified solution to obtain a graphene-para-aramid nanofiber-chitosan composite modified solution; The p-aramid nanofiber-chitosan composite modified solution in step (3) is replaced by the graphene-p-aramid nanofiber-chitosan composite modified solution.

9. The surface modification method of the para-aramid fiber polyurethane resin composite material according to claim 8, characterized in that: The specific steps of preparing the graphene nanoparticles into a graphene nanoparticle dispersion in step (21) are: fully dissolving the graphene nanoparticles in an ethanol aqueous solution to obtain the graphene nanoparticle dispersion.

10. A para-aramid fiber polyurethane resin surface modified composite material, characterized in that: The composite material is prepared by the surface modification method of the para-aramid fiber polyurethane resin composite material according to any one of claims 4 to 9.

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