Aramid fiber surface grafting polymerization modification reinforced protective material and preparation method

Abstract

The application relates to the technical field of aramid fiber modification, in particular to aramid surface grafting polymerization modified reinforced protective material and a preparation method, the preparation method comprises the following steps: preparing an acid mixed solution, acidizing diatomite DE; preparing CNTs based on the acidized diatomite DE; preparing an excessive matrix; preparing an ammonium polyphosphate modified material; preparing melamine formaldehyde resin; preparing a core-shell microcapsulated ammonium polyphosphate modified material; roughening the surface of the fiber; modifying the interface of the fiber; preparing a composite fiber material; and the protective material prepared by the above preparation method, the application has the beneficial effects that macroscopic grafting behavior is combined with the evolution of microstructure, the crystal structure of the original substance is kept in good integrity in the preparation process, the bulletproof performance of the fabric is significantly enhanced, the penetration resistance of the composite material is greatly enhanced, and a reliable research foundation is provided for the exploration of the protective performance of the composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aramid fiber modification, in particular to an aramid surface grafting and polymerization modified reinforced protective material and a preparation method. BACKGROUND

[0002] The international environment is changing constantly, and local wars and terrorist attacks occur from time to time, and a large number of soldiers are killed and wounded in the battlefield every year. The main battlefield damage factors are fragments, shock waves, high-temperature combustion, laser strikes, etc., and the bullet and fragment penetration is the main factor of the soldier casualties. Individual protective equipment has become the top priority for soldier protection, and how to achieve higher strength protection has become the key point of individual protection. Bulletproof materials are mainly divided into hard materials, soft materials and composite structures, and soldiers in complex battlefield environments face long-time combat. Although hard materials and composite structure materials have good protective performance, the comfort, softness and lightweight will affect the overall ability of the soldiers. In the process of previous military operations, a large number of soldiers suffered severe pressure on the spine and shoulders due to long-time wearing of heavy equipment, resulting in low combat efficiency. Therefore, the research on soft materials to provide a high-performance soft material with lightweight and protective performance has become a major issue in the field of individual protective materials. SUMMARY

[0003] In order to solve the problems in the prior art, the present application provides an aramid surface grafting and polymerization modified reinforced protective material and a preparation method, to solve the problems of lightweight and bulletproof performance of individual protective materials.

[0004] To solve the above problems, the technical scheme of the present application is as follows, the preparation method of the aramid surface grafting and polymerization modified reinforced protective material comprises the following steps,

[0005] S1 preparation of an acidic mixed solution;

[0006] Methyltriethoxysilane MTES is used as a precursor, anhydrous ethanol EtOH is used as a solvent, methyltriethoxysilane MTES is added to a mixed solution of hydrochloric acid HCl and anhydrous ethanol EtOH, and the mass ratio of the methyltriethoxysilane MTES, HCl and EtOH is 1:1-2:1-2, to obtain an acidic mixed solution;

[0007] S2 acidification treatment of diatomite DE;

[0008] S3 preparation of CNTs based on the acidified diatomite DE;

[0009] S4 preparation of a matrix; the CNTs prepared in S3 are acid-modified, ultrasonically dispersed and washed to neutral to obtain a matrix CNTs-OH;

[0010] S5 preparation of an ammonium polyphosphate modified material;

[0011] S6 melamine formaldehyde resin preparation;

[0012] S7 core-shell microencapsulated ammonium polyphosphate modified material preparation;

[0013] S8 fiber surface roughening treatment;

[0014] The aramid fiber AF is immersed in the ethanol solution for 0.5 h, and the ethanol covers the entire fiber;

[0015] S9 fiber interface modification treatment;

[0016] S10 composite fiber material preparation;

[0017] The core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR prepared in S7 is placed in a medium solution, and the modified fiber prepared in S9 is placed in the core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR suspension, ultrasonic dispersion is carried out at room temperature for 1 h, and the operation is repeated for 3 times. The treated fiber is dried in a drying oven at 90℃ for 24 h, and the loaded composite fiber APP@CNTs-MFR / AF is obtained.

[0018] Further, the acidification treatment step S2 is that the acid mixed solution obtained in S1 is stirred at a speed of 500 rpm for 12 h at room temperature, diatomite DE is placed in the acid mixed solution, and drying treatment is carried out at 60-80℃ to obtain acidified diatomite DE.

[0019] Further, step S3 includes that the acidified diatomite DE is modified by nickel nitrate (0.01-0.2 mol·L-1) induction, and black solid powder CNTs is synthesized by chemical vapor deposition method in an inert gas (nitrogen, etc.) atmosphere.

[0020] Further, the acid modification in step S4 adopts concentrated sulfuric acid and concentrated nitric acid.

[0021] Further, the method of step S5 is that CNTs-OH is weighed and placed in 4-dimethylaminopyridine DMAP, polyacrylic acid PAA, and dimethylacetamide DMF interface grafting induction solution, and the mass ratio is 1-2:1-3:1-3:1-3, so as to obtain carboxylated carbon nanotube CNTs-COOH. Ammonium polyphosphate APP is dissolved in distilled water, and the mass ratio is 1:2-8. The carboxylated carbon nanotube CNTs-COOH is placed in anhydrous ethanol, and the mass ratio is 1:2-8. The two are mixed to carry out solvent crystallization method to obtain ammonium polyphosphate modified material APP@CNTs.

[0022] Further, step S6 is to dissolve melamine and formaldehyde with a mass ratio of 1:2-8, adjust pH to 8-9 by using sodium carbonate aqueous solution, heat in a water bath at 80-100 DEG C and continuously stir, and after filtration, washing and drying, melamine formaldehyde resin MFR is obtained.

[0023] Further, step S7 includes adding APP@CNTs modified material and melamine formaldehyde resin MFR to anhydrous ethanol EtOH solution in a ratio of 2-8:1, stirring uniformly, adjusting pH to 3-4 by passing in sulfuric acid, high-temperature reaction and drying for 12 hours, to obtain core-shell microencapsulated APP@CNTs-MFR.

[0024] Further, step S9 includes placing the fibers obtained in S8 in a mixed solution of ethanol and silane coupling agent in a mass ratio of 8-12:1, and placing the mixed liquid in a magnetic stirrer for 1 hour.

[0025] Further, the medium solution in step S10 is mainly mixed by ethanol and distilled water in a ratio of 1-2:1-2.

[0026] The aramid fiber surface grafting polymer modified reinforced protective material is prepared by using the above preparation method.

[0027] Compared with the prior art, the application has the following beneficial effects: 1. The preparation method of APP@CNTs-MFR / AF combines macro-grafting behavior with microstructure evolution, and innovatively explores the basic mechanical properties and impact resistance of APP@CNTs-MFR / AF.

[0028] 2. The diatomite DE is modified and the functional groups are grafted on the surface, and by surface modification, APP@CNTs-MFR is successfully prepared, and APP@CNTs-MFR is successfully grafted, which also shows that the crystal structure of the original substance is well maintained during the synthesis of APP@CNTs-MFR.

[0029] 3. APP@CNTs-MFR / AF significantly enhances the bulletproof performance of the fabric, and the impregnation method and the grafting of the particles greatly enhance the penetration resistance of the composite material, providing a reliable research basis for the exploration of the protective performance of the composite material. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The figure is a schematic diagram of the interface grafting modification. DETAILED DESCRIPTION

[0031] Example 1:

[0032] As Figure 1As shown, it is the interface grafting modification schematic diagram, the preparation method of aramid fiber surface grafting polymerization modification reinforced protective material, including the following steps:

[0033] S1 acid mixed solution preparation;

[0034] Diatomite DE is a natural environmental protection material, DE is used as a silicon source, methyltriethoxysilane MTES is used as a precursor, and anhydrous ethanol EtOH is used as a solvent, a regenerated utilization method is used to reduce resource waste and protect the environment, MTES is added to a mixed solution of hydrochloric acid HCl and anhydrous ethanol EtOH, the mass ratio of HCl and EtOH is 1:1:1, so that the reaction state becomes an acidic reaction environment;

[0035] S2 diatomite DE acidification treatment;

[0036] The mixed solution is stirred at a speed of 500 rpm for 12 h, the solution can be carried out at room temperature, so that the precursor MTES is fully reacted in the acidic solution, the diatomite is mixed in the acidic precursor solution, and drying treatment is carried out at 60-80 DEG C;

[0037] S3 preparation of CNTs based on acidified diatomite DE;

[0038] The acidified and dried diatomite DE is taken and modified by nickel nitrate (0.01-0.2 mol·L -1 ) induction, and then black solid powder CNTs is synthesized by chemical vapor deposition method in an inert gas (nitrogen, etc.) atmosphere;

[0039] S4 over matrix preparation;

[0040] In order to prepare a flame-retardant heat-insulating matrix, the CNTs are acid modified (concentrated sulfuric acid and concentrated nitric acid), ultrasonically dispersed and washed to neutral, so that the over matrix CNTs-OH can be obtained;

[0041] S5 preparation of ammonium polyphosphate modified material;

[0042] The CNTs-OH is weighed and placed in 4-dimethylaminopyridine DMAP, polyacrylic acid PAA and dimethylacetamide DMF interface grafting induction liquid, the mass ratio is 1:2:2:2, so that the carboxylated carbon nanotube CNTs-COOH is obtained, the ammonium polyphosphate APP is dissolved in distilled water, the mass ratio is 1:5, the CNTs-COOH is placed in anhydrous ethanol, the mass ratio is 1:5, and the ammonium polyphosphate modified material APP@CNTs is obtained by mixing the two for solution crystallization;

[0043] S6 melamine formaldehyde resin preparation;

[0044] Melamine and formaldehyde are dissolved in a mass ratio of 1:5, and the pH is adjusted to 8-9 by sodium carbonate aqueous solution. Melamine formaldehyde resin MFR is obtained by filtering, washing and drying under the condition of 80-100℃ water bath heating and continuous stirring.

[0045] S7 Preparation of core-shell microencapsulated ammonium polyphosphate modified material

[0046] APP@CNTs and MFR are added to anhydrous ethanol solution in a ratio of 5:1, stirred uniformly, and the pH value is adjusted to 3-4 by sulfuric acid. Core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR is obtained by high temperature reaction and drying for 12h.

[0047] S8 Rough treatment of fiber surface

[0048] In order to better realize the combination of core-shell microencapsulated ammonium polyphosphate modified material and fiber fabric and enhance the friction performance, the fiber surface is roughened in the past research to increase the contact area of the fiber surface and better realize the particle adhesion. Aramid fiber AF is immersed in a mixed solution of ethanol for 0.5h, and the fiber is completely covered with ethanol.

[0049] S9 Interfacial modification treatment of fiber

[0050] The immersed fiber is placed in a mixed solution mainly composed of ethanol and silane coupling agent in a mass ratio of 10:1, and the mixed liquid is placed in a magnetic stirrer for 1h. The schematic diagram of interfacial grafting modification is shown in the figure.

[0051] S10 Preparation of composite fiber material

[0052] The core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR is placed in a medium solution mainly composed of ethanol and distilled water in a ratio of 1:2. Finally, the fiber immersed in the mixed coupling agent is placed in the core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR suspension, and ultrasonic dispersion is carried out at room temperature for 1h. In order to ensure uniform immersion, the sample needs to be repeated three times. The fabric after immersion is rolled by a mangle to remove the excess diluent and at the same time to make the shear thickening liquid fully penetrate into the gap between the fibers. In order to ensure uniform loading and reduce experimental error, the treated fiber is dried in a 90℃ oven for 24h to obtain the loaded fiber APP@CNTs-MFR / AF.

[0053] On the basis of the preparation of composite fiber material, the fiber APP@CNTs-MFR / AF with completed loading is obtained. APP@CNTs-MFR can effectively adhere to the surface of aramid fiber, and the connectivity and compatibility are good, without serious void and particle aggregation phenomenon. Physical property test is carried out, and the related test description is as follows:

[0054] 1. Area density test

[0055] The area density of the fabric after immersion treatment is in the range of 232 to 246 g / cm 2 , compared with the area density of 200 g / cm 2 of pure fabric. The mass gain of the immersed fabric is between 16% and 23%.

[0056] 2. Friction behavior between yarns

[0057] When the pull-out test is carried out on aramid fabric and modified fabric, the slip between yarns has an important influence on the mechanical properties of the fabric, which is also directly reflected in the friction behavior between yarns. In the past, scholars directly proved the difference in internal friction of the whole fabric by pull-out test, mainly by regarding the pull-out force as a function of friction coefficient and normal pressure F = f(μ, F N ). When the weaving structure of aramid fiber is the same, the normal contact force F N during pull-out is approximately considered as a constant, and it can be inferred that F ∝ μ.

[0058] Single yarn pull-out test selects the test device. When placing the sample, the lower edge of the sample is clamped, and the upper edge is free to move. In order to avoid generating pre-tension force in the yarn, the yarn is clamped loosely. The central yarn is selected for pull-out test. The size of the experimental sample fabric is 16 mm long and 4 mm wide. The central warp yarn is pulled out at a speed of 10 mm / min, 50 mm / min, 100 mm / min and 200 mm / min, respectively, and the load-displacement data is recorded by software.

[0059] After loading APP@CNTs-MFR, the pull-out force of the fiber yarn is obviously improved, and the fiber surface and gap are full of liquid and dispersed phase particles. The maximum yarn pull-out force of APP@CNTs-MFR / AF composite fabric is 3 times that of pure AF fabric.

[0060] 3. Determination of combustion performance by oxygen index method

[0061] According to the method recorded in GB / T5454-1997 "Determination of combustion performance of textiles by oxygen index method", the limiting oxygen index test of the flame-retardant fabric prepared by examples 1-9 and comparative examples is carried out. Generally, it is considered that the LOI value below 20% is flammable fiber, between 20% and 26% is combustible fiber, between 26% and 34% is difficult to burn fiber, and above 35% is non-combustible fiber.

[0062] The flame retardant performance of the prepared composite fabric and the original fabric was tested three times respectively, and the APP@CNTs-MFR / AF aramid fabric was 30.5%, the flame retardant effect was synergistically enhanced, and the APP@CNTs-MFR / AF achieved excellent technical effect.

[0063] 4. Ballistic test performance

[0064] In order to evaluate the ballistic performance of APP@CNTs-MFR / AF fabric and pure AF fabric, a high pressure ballistic impact device was used for testing. The bullet used in the ballistic impact was a spherical steel ball with a diameter of 5 mm. The bullet power was mainly obtained from the high pressure gas in the gas tank. By changing the pressure of the high pressure gas, the bullet incident speed of 40-300 m / s was obtained.

[0065] Two high-speed photography equipment were used in the experiment. One of them mainly recorded the instantaneous speed before and after the bullet impact, and calculated the ballistic limit speed (V50) of the experimental sample according to the incident speed and residual speed; the other recorded the back jump distance and fiber fracture mode at the bullet impact position. The outer size of the target plate was 18x18cm, and the inner window size was 16x16cm. The four corners were fixed, and the four corners of the sample were clamped by stainless steel frame.

[0066] The ballistic limit speed of APP@CNTs-MFR / AF was 97m / s, but APP@CNTs-MFR had the characteristics of mass weight gain for AF, so the specific energy absorption (SEA) of the fabric was selected to study the unit area density of the fiber. The greater the SEA, the greater the kinetic energy absorbed by the bullet by the unit area density of the bulletproof material, and the better the bulletproof performance.

[0067] 5. Comparison test of multi-layer laminated ballistic limit speed

[0068] The ballistic limit of APP@CNTs-MFR / AF for one layer, two layers and three layers was tested. In order to facilitate comparison, the corresponding APP@CNTs-MFR / AF was named as APP@CNTs-MFR / AF 1 # , APP@CNTs-MFR / AF 2 # , APP@CNTs-MFR / AF 3 # . Through the test of ballistic limit and energy absorption efficiency of each layer of APP@CNTs-MFR / AF and AF fabric, it was found that the ballistic limit of APP@CNTs-MFR / AF one layer, two layers and three layers was 97m / s, 126m / s and 151m / s respectively. When the number of layers was gradually increased, although the SEA and η enhancement ratio did not show a linear correlation, it could be obviously seen that they were significantly improved.

[0069] 6. Back projection change morphology and back projection height contrast test

[0070] The AF fabric impregnated by SA gel has a back projection size of 2.12-2.63 cm, which greatly reduces the back projection height. On the contrary, the main failure mode of APP@CNTs-MFR / AF fabric is yarn breakage, and the transverse sliding distance is also significantly reduced. This is mainly because APP@CNTs-MFR / AF has better friction effect, and when the projectile impacts the fabric, it will dissipate part of the energy. Moreover, the presence of APP@CNTs-MFR increases the friction between the fabric and the projectile, and also enhances the friction between the yarns, which promotes the transmission of local energy to more secondary yarns to participate in hindering the movement of the projectile.

[0071] Example 2:

[0072] The preparation method of aramid surface grafting polymerization modified reinforced protective material comprises the following steps:

[0073] S1 preparation of an acidic mixed solution;

[0074] Diatomaceous earth DE is a natural and environmentally friendly material. DE is used as a silicon source, methyltriethoxysilane MTES is used as a precursor, and anhydrous ethanol EtOH is used as a solvent. By recycling, resource waste is reduced, and the environment is protected. MTES is added to a mixed solution of hydrochloric acid HCl and anhydrous ethanol EtOH, and the mass ratio of HCl to EtOH is 1:1:1, so that the reaction state becomes an acidic reaction environment;

[0075] S2 acidification treatment of diatomaceous earth DE;

[0076] The mixed solution is stirred at a speed of 500 rpm for 12 hours, and the solution can be performed at room temperature, so that the precursor MTES is fully reacted in the acidic solution. The diatomaceous earth is mixed in the acidic precursor solution and dried at 60-80°C;

[0077] S3 preparation of CNTs based on acidified diatomaceous earth DE;

[0078] The acidified and dried diatomaceous earth DE is modified by nickel nitrate (0.01-0.2 mol·L -1 ) induction, and then black solid powder CNTs is synthesized by chemical vapor deposition method in an inert gas (nitrogen, etc.) atmosphere;

[0079] S4 preparation of excessive matrix;

[0080] In order to prepare a flame-retardant and heat-insulating matrix, the CNTs are acid modified (concentrated sulfuric acid and concentrated nitric acid), ultrasonically dispersed, and washed to neutral, so as to obtain the excessive matrix CNTs-OH;

[0081] S5 preparation of ammonium polyphosphate modified material;

[0082] The CNTs-OH is weighed and placed in an interfacial grafting inducement solution of 4-dimethylaminopyridine DMAP, polyacrylic acid PAA, dimethylacetamide DMF, with a mass ratio of 1:1:1:1, to obtain carboxylated carbon nanotubes CNTs-COOH. Ammonium polyphosphate APP is dissolved in distilled water with a mass ratio of 1:2, and the CNTs-COOH is placed in anhydrous ethanol with a mass ratio of 1:2. The ammonium polyphosphate modified material APP@CNTs is obtained by mixing the two for solvated crystallization.

[0083] S6 Melamine formaldehyde resin preparation

[0084] The melamine is dissolved in formaldehyde with a mass ratio of 1:2, and the pH is adjusted to a weak alkalinity of 8-9 using a sodium carbonate aqueous solution. The mixture is heated in a water bath at 80-100°C with constant stirring. After filtration, washing and drying, the melamine formaldehyde resin MFR is obtained.

[0085] S7 Core-shell microencapsulated ammonium polyphosphate modified material preparation

[0086] The APP@CNTs and MFR are added to an anhydrous ethanol solution in a ratio of 2:1, stirred uniformly, and the pH value is adjusted to a strong acidity of 3-4 by sulfuric acid. High-temperature reaction and drying for 12h obtain the core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR.

[0087] S8 Fiber surface roughening treatment

[0088] In order to better realize the combination of the core-shell microencapsulated ammonium polyphosphate modified material and the fiber fabric and enhance the friction performance, the fiber surface is roughened in previous studies to increase the fiber surface contact area and better realize particle adhesion. The aramid fiber AF is immersed in the mixed ethanol solution for 0.5h, and the ethanol covers the fiber completely.

[0089] S9 Fiber interface modification treatment

[0090] The immersed fiber is placed in a mixed solution mainly composed of ethanol and silane coupling agent with a mass ratio of 8:1. The mixed liquid is placed in a magnetic stirrer for 1h. The interface grafting modification schematic diagram is shown in the figure.

[0091] S10 Composite fiber material preparation

[0092] The core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR is placed in a medium solution, which is mainly a mixture of ethanol and distilled water in a ratio of 1:1. Finally, the ethanol and coupling agent mixed impregnated fiber is placed in the core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR suspension, and ultrasonic dispersion is carried out at room temperature for 1 h. In order to ensure uniform impregnation, the sample needs to be repeated 3 times. After impregnation, the fabric is passed through the mangle to remove the excess diluent while allowing the shear thickening fluid to fully penetrate into the gaps between the fibers. In order to ensure uniform impregnation and reduce experimental error, the experiment needs to be repeated three times. The treated fiber is dried in a 90°C oven for 24 h to obtain the loaded fiber APP@CNTs-MFR / AF.

[0093] Based on the preparation of composite fiber material, the loaded fiber APP@CNTs-MFR / AF is obtained. APP@CNTs-MFR can effectively adhere to the surface of aramid fiber, and the connectivity and compatibility are good, without serious void and particle molecular aggregation phenomenon. Physical performance test is carried out, and the related test instructions are as follows:

[0094] 1. Area density test

[0095] The area density of the fabric after impregnation treatment is in the range of 229 to 240 g / cm 2 , compared with the area density of 200 g / cm 2 of pure fabric.

[0096] 2. Yarn interlaminar friction behavior

[0097] When the aramid fabric and the modified fabric are subjected to pull-out test, the interlaminar slip of yarn has an important influence on the mechanical properties of the fabric, which is also directly reflected in the friction behavior between yarns. In the past, scholars directly proved the difference in internal friction of the whole fabric through pull-out test, mainly by regarding the pull-out force as a function of friction coefficient and normal pressure F=f(μ,F N ). When the weaving structure of aramid fiber is the same, the normal contact force F N during pull-out is approximately considered as a constant, and it can be inferred that F∝μ.

[0098] Single yarn pull-out test selects a test device. When placing the sample, the lower edge of the clamped experimental sample is clamped, and the upper edge is freely moved. In order to avoid generating pre-tension force in the yarn, the yarn is clamped loosely. The central yarn is selected for pull-out test. The size of the experimental sample fabric is 16 mm long and 4 mm wide. The central warp yarn is pulled out at a speed of 10 mm / min, 50 mm / min, 100 mm / min and 200 mm / min, respectively. The load-displacement data is recorded by software.

[0099] After APP@CNTs-MFR loading, the pull force of the fiber yarns is obviously improved, and the fiber surface and gaps are filled with liquid and dispersed phase particles. The maximum yarn pull force of the APP@CNTs-MFR / AF composite fabric is 2.5 times that of the pure AF fabric.

[0100] 3. Combustion performance determination oxygen index method

[0101] According to the method recorded in GB / T5454—1997 “Textile Combustion Performance Determination Oxygen Index Method”, the limiting oxygen index test is performed on the flame-retardant fabric prepared from Examples 1-9 and Comparative Examples. Generally, it is considered that the LOI value below 20% is flammable fiber, between 20% and 26% is combustible fiber, between 26% and 34% is difficult to burn fiber, and above 35% is non-combustible fiber.

[0102] The prepared composite fabric and the original fabric are respectively tested for three times of flame-retardant performance, and the APP@CNTs-MFR / AF aramid fabric is 29.6%, the flame-retardant effect is synergistically enhanced, and the APP@CNTs-MFR / AF achieves excellent technical effect.

[0103] 4. Ballistic test performance

[0104] In order to compare and evaluate the ballistic performance of APP@CNTs-MFR / AF fabric and pure AF fabric, a high-pressure ballistic impact device is used for testing. The bullet used for ballistic impact is a spherical steel ball with a diameter of 5 mm. The bullet power is mainly obtained from the high-pressure gas in the gas tank. By changing the pressure of the high-pressure gas, the bullet incident speed of 40-300 m / s is obtained.

[0105] Two high-speed photography equipment are used in the experiment. One of them mainly records the instantaneous speed before and after the bullet impact, and calculates the ballistic limit speed (V50) of the experimental sample according to the incident speed and residual speed; the other records the back jump distance at the bullet impact position and the fiber fracture mode. The outer size of the target plate is 18x18cm, the inner window size is 16x16cm, and the four corners are fixed by selecting a stainless steel frame to hold the four corners of the sample. The ballistic limit speed of APP@CNTs-MFR / AF is 88m / s.

[0106] 5. Comparison test of multi-layer laminated ballistic limit speed

[0107] The ballistic limit of APP@CNTs-MFR / AF for one layer, two layers and three layers is tested. In order to facilitate comparison, the corresponding APP@CNTs-MFR / AF is named as APP@CNTs-MFR / AF 1 # , APP@CNTs-MFR / AF 2 # , APP@CNTs-MFR / AF 3 #The ballistic limit and energy absorption efficiency of each layer of the APP@CNTs-MFR / AF and AF fabric are tested, and the experimental results show that the ballistic limit of the APP@CNTs-MFR / AF one-layer two-layer three-layer is 88 m / s, 115 m / s, 139 m / s respectively, and when the number of layers is gradually increased, although the SEA and η enhancement ratio does not show a linear correlation, it can be seen that it is significantly improved.

[0108] 6. Back protrusion change morphology and back protrusion height comparison test

[0109] The back protrusion size of the AF fabric immersed in the SA gel is 2.4-2.8 cm, which greatly reduces the back protrusion height. On the contrary, the main failure mode of the APP@CNTs-MFR / AF fabric is yarn fracture, and the transverse sliding distance is also significantly reduced. This is mainly because APP@CNTs-MFR / AF has a better friction effect, and when the projectile impacts the fabric, part of the energy is dissipated, and the presence of APP@CNTs-MFR increases the friction between the fabric and the projectile, and also enhances the friction between the yarns, which promotes the local energy to be transmitted to more secondary yarns to participate in hindering the movement of the projectile.

[0110] Example 3:

[0111] As Figure 1 shown, is an interface grafting modification schematic diagram, a preparation method of aramid fiber surface grafting polymerization modification reinforced protective material, including the following steps:

[0112] S1 preparation of an acidic mixed solution;

[0113] Diatomaceous earth DE is a natural and environmentally friendly material. DE is used as a silicon source, methyltriethoxysilane MTES is used as a precursor, and anhydrous ethanol EtOH is used as a solvent. By recycling, resource waste is reduced, and the environment is protected. MTES is added to a mixed solution of hydrochloric acid HCl and anhydrous ethanol EtOH, and the mass ratio of HCl to EtOH is 1:2:2, so that the reaction state becomes an acidic reaction environment;

[0114] S2 acidification treatment of diatomaceous earth DE;

[0115] The mixed solution is stirred at a speed of 500 rpm for 12 hours, and the solution can be performed at room temperature, so that the precursor MTES is fully reacted in the acidic solution. The diatomaceous earth is mixed in the acidic precursor solution and dried at 60-80°C;

[0116] S3 preparation of CNTs based on acidified diatomaceous earth DE;

[0117] The acidified and dried diatomaceous earth DE is taken and mixed with nickel nitrate (0.01-0.2 mol·L -1Induced modification, then by chemical vapor deposition method, inert gas (nitrogen, etc.) atmosphere synthesis of black solid powder CNTs;

[0118] S4 excessive matrix preparation;

[0119] In order to prepare the flame-retardant thermal insulation matrix, the CNTs are acid modified (concentrated sulfuric acid and concentrated nitric acid), ultrasonic dispersion and then washed to neutral, so as to obtain the excessive matrix CNTs-OH;

[0120] S5 preparation of ammonium polyphosphate modified material;

[0121] The CNTs-OH is weighed and placed in the interfacial grafting induction solution of 4-dimethylaminopyridine DMAP, polyacrylic acid PAA and dimethylacetamide DMF, and the mass ratio is 2:3:3:3, so as to obtain the carboxylated carbon nanotube CNTs-COOH. The ammonium polyphosphate APP is dissolved in distilled water, and the mass ratio is 1:8. The CNTs-COOH is placed in anhydrous ethanol, and the mass ratio is 1:8. The ammonium polyphosphate modified material APP@CNTs is obtained by mixing the two through solvent crystallization method.

[0122] S6 preparation of melamine formaldehyde resin;

[0123] The melamine is dissolved with formaldehyde, and the mass ratio is 1:8. The pH is adjusted to 8-9 by sodium carbonate aqueous solution to be slightly alkaline. The water bath is heated at 80-100℃ and continuously stirred. After filtration, washing and drying, the melamine formaldehyde resin MFR is obtained.

[0124] S7 preparation of core-shell microencapsulated ammonium polyphosphate modified material;

[0125] The APP@CNTs and MFR are added to anhydrous ethanol solution in a proportion of 8:1, stirred uniformly, and the pH value is adjusted to 3-4 by sulfuric acid to be strongly acidic. High temperature reaction and drying for 12h, the core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR is obtained.

[0126] S8 roughening treatment of fiber surface;

[0127] In order to better realize the combination of core-shell microencapsulated ammonium polyphosphate modified material and fiber fabric and enhance the friction performance, the fiber surface is roughened in the past research, the fiber surface contact area is increased, and the particle adhesion is better. The aramid fiber AF is immersed in the mixed solution of ethanol for 0.5h, and the ethanol covers the fiber completely;

[0128] S9 fiber interface modification treatment;

[0129] The impregnated fiber is placed in a mixed solution mainly composed of ethanol and silane coupling agent with a mass ratio of 12:1, and the mixed liquid is placed in a magnetic stirrer for 1 h; the schematic diagram of interfacial grafting modification is shown in the figure;

[0130] S10 composite fiber material preparation;

[0131] The core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR is placed in a medium solution mainly composed of ethanol and distilled water mixed in a ratio of 2:2, and finally the ethanol and coupling agent mixed impregnated fiber is placed in the core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR suspension, ultrasonic dispersion for 1 h at room temperature, in order to ensure uniform impregnation, the sample needs to be repeated for 3 times, the impregnated fabric is rolled by a roller to remove the excess diluent and at the same time make the shear thickening liquid fully penetrate into the gap between the fabric fibers, in order to ensure uniform impregnation and reduce experimental error, the treated fiber is dried in a 90°C oven for 24 h to obtain the loaded fiber APP@CNTs-MFR / AF.

[0132] On the basis of the preparation of the composite fiber material, the loaded fiber APP@CNTs-MFR / AF is obtained, APP@CNTs-MFR can effectively adhere to the surface of aramid fiber, the connectivity and compatibility are good, and there is no serious void and particle molecular aggregation phenomenon. Physical performance test is carried out, and the related test instructions are as follows:

[0133] 1. Area density test

[0134] The area density of the impregnated fabric is in the range of 215 to 225 g / cm 2 , compared with the area density of 200 g / cm 2 of pure fabric.

[0135] 2. Yarn interfacial friction behavior

[0136] When the aramid fabric and the modified fabric are subjected to pull-out test, the interfacial friction between the yarns has an important influence on the mechanical properties of the fabric, which is also directly reflected in the interfacial friction behavior. In the past, scholars directly proved the difference in interfacial friction of the whole fabric by pull-out test, mainly by considering that the pull-out force can be regarded as a function of friction coefficient and normal pressure F=f(μ,F N ). When the weaving structure of aramid fiber is the same, the normal contact force F N during pull-out is approximately considered as a constant, which can be inferred that F∝μ.

[0137] The single yarn pull-out test selects the test device, and when placing the sample, the lower edge of the test sample is clamped, and the upper edge is freely moved. In order to avoid generating pre-tension force in such yarns, the yarns are clamped loosely. The central yarn is selected for the pull-out test, and the size of the test sample fabric is 16 mm long and 4 mm wide. The central warp yarn is pulled out at a speed of 10 mm / min, 50 mm / min, 100 mm / min and 200 mm / min, and the load-displacement data is recorded by software.

[0138] After APP@CNTs-MFR is loaded, the pull-out force of the fiber yarn is obviously improved, and the fiber surface and gap are filled with liquid and dispersed phase particles. The maximum yarn pull-out force of the APP@CNTs-MFR / AF composite fabric is 1.9 times that of the pure AF fabric.

[0139] 3. Combustion performance determination oxygen index method

[0140] According to the method recorded in GB / T5454—1997 "Textile Combustion Performance Determination Oxygen Index Method", the flame-retardant fabric prepared by Examples 1-9 and Comparative Examples is subjected to limiting oxygen index test. Generally, it is considered that the LOI value below 20% is flammable fiber, between 20% and 26% is combustible fiber, between 26% and 34% is difficult to burn fiber, and above 35% is non-combustible fiber.

[0141] The prepared composite fabric and the original fabric are respectively subjected to three times of flame-retardant performance test, the APP@CNTs-MFR / AF aramid fabric is 29.5%, the flame-retardant effect is synergistically enhanced, and the APP@CNTs-MFR / AF achieves excellent technical effect.

[0142] 4. Ballistic test performance

[0143] In order to compare and evaluate the ballistic performance of APP@CNTs-MFR / AF fabric and pure AF fabric, a high-pressure ballistic impact device is used for testing. The bullet used for ballistic impact is a spherical steel ball with a diameter of 5 mm. The bullet power is mainly obtained from the high-pressure gas in the gas tank. By changing the pressure of the high-pressure gas, the bullet incident speed of 40-300 m / s is obtained.

[0144] Two high-speed photography equipment are used in the experiment. One of them mainly records and measures the instantaneous speed before and after the bullet impact, and calculates the ballistic limit speed (V50) of the experimental sample according to the incident speed and residual speed; the other records the back projection distance at the bullet impact position and the fiber fracture mode. The outer size of the target plate is 18x18cm, the inner window size is 16x16cm, and the four corners are fixed by selecting stainless steel frame to clamp the four corners of the sample.

[0145] The ballistic limit velocity of APP@CNTs-MFR / AF is 78 m / s, but APP@CNTs-MFR has the characteristic of mass gain of AF, so the specific energy absorption (SEA) of the fabric is selected to study the unit area density of the fiber, the greater the SEA, the greater the kinetic energy absorbed by the unit area density of the ballistic material, and the better the ballistic performance.

[0146] 5. Multi-layer ballistic limit velocity comparison test

[0147] The ballistic limit of APP@CNTs-MFR / AF for one layer, two layers and three layers is tested, and for convenience of comparison, the corresponding APP@CNTs-MFR / AF is named as APP@CNTs-MFR / AF 1 # , APP@CNTs-MFR / AF 2 # , APP@CNTs-MFR / AF 3 # . Through the test of the ballistic limit and energy absorption efficiency of each layer of APP@CNTs-MFR / AF and AF fabric, the experimental results show that the ballistic limit of APP@CNTs-MFR / AF one layer, two layers and three layers is 78 m / s, 106 m / s and 135 m / s respectively, and when the number of layers is gradually increased, although the SEA and η enhancement ratio does not show a linear correlation, it can be obviously seen that it is significantly improved.

[0148] 6. Comparison test of back protrusion change form and back protrusion height

[0149] The back protrusion size of AF fabric impregnated with SA gel is 2.51-2.88 cm, which greatly reduces the back protrusion height. On the contrary, the main failure mode of APP@CNTs-MFR / AF fabric is yarn breakage, and the transverse sliding distance is also significantly reduced. This is mainly because APP@CNTs-MFR / AF has better friction effect, and part of the energy is dissipated when the projectile impacts the fabric, and the presence of APP@CNTs-MFR increases the friction between the fabric and the projectile, and also enhances the friction between the yarns, which promotes the local energy to be transmitted to more secondary yarns to participate in hindering the movement of the projectile.

[0150] Comparative example:

[0151] 1. Area density test

[0152] The area density of pure fabric is 200 g / cm 2

[0153] 2. Friction behavior between yarns

[0154] ​The single yarn pull-out test selects the test device, and when placing the sample, the lower edge of the clamped experimental sample is clamped, and the upper edge is freely moved. In order to avoid generating pre-tension in such yarns, the yarns are clamped loosely. The central yarn is selected for the pull-out test, and the experimental sample fabric size is 16 mm long and 4 mm wide. The central warp yarn is pulled out at a speed of 10 mm / min, 50 mm / min, 100 mm / min and 200 mm / min, and the load-displacement data is recorded by software.

[0155] The maximum pull-out force of the pure AF fabric is 5.3N, and it changes slightly with the pull-out rate, mainly because the surface of the AF fiber is smooth and flat, there is a large gap between the fibers, the interaction between the yarns is low, and the pull-out movement is easy, and the relationship with the pull-out speed is small.

[0156] 3. Combustion performance determination oxygen index method

[0157] According to the method recorded in GB / T5454—1997 "Textile combustion performance determination oxygen index method", the limiting oxygen index test is carried out on the flame-retardant fabric prepared by examples 1-9 and comparative examples. Generally, it is considered that the LOI value is lower than 20% for flammable fiber, between 20% and 26% for combustible fiber, between 26% and 34% for difficult flammable fiber, and above 35% for non-flammable fiber.

[0158] The prepared composite fabric and the original fabric are respectively tested for three times of flame-retardant performance, and finally the oxygen index LOI value of the original fabric is 29.3%.

[0159] 4. Ballistic test performance

[0160] In order to compare and evaluate the ballistic performance of APP@CNTs-MFR / AF fabric and pure AF fabric, high pressure ballistic impact device is used for test, the bullet used for ballistic impact is a spherical steel ball with a diameter of 5mm, the bullet power is mainly obtained from the high pressure gas in the gas tank, and the bullet incident speed of 40-300m / s is obtained by changing the high pressure gas pressure.

[0161] Two high-speed photography equipments are used in the experiment, one of which mainly records and measures the instantaneous speed before and after the bullet impact, and calculates the ballistic limit speed (V50) of the experimental sample according to the incident speed and residual speed; the other records the back projection distance at the bullet impact position and the fiber fracture mode. The outer size of the target plate is 18x18cm, the inner window size is 16x16cm, the four corners are fixed, and the four corners of the sample are clamped by stainless steel frame.

[0162] The ballistic limit of pure AF fabric is 51m / s, and the SEA value of AF is 0.00125J·m 2 / kg.

[0163] 5. Multi-layered laminated ballistic limit velocity comparison test

[0164] For the convenience of comparison, the first layer of pure AF fabric is named AF 1 # , the second layer is named AF 2 # , and the third layer is named AF 3 # ; the SEA and η of the AF fabric are 51 m / s, 95 m / s, and 128 m / s, respectively, and although the increasing proportion of SEA and η does not show a linear correlation when the number of layers is gradually increased, it can be seen that there is a significant improvement.

[0165] 6. Comparison test of back protrusion change pattern and back protrusion height

[0166] The back protrusion size of the pure AF fabric is between 3.26-4.11 mm, and the projectile impact on the warp and weft yarns of the pure AF fabric forms a large area of “window effect”, and the failure mode is mainly yarn deformation and stretching.

[0167] The above specific embodiments are only used to illustrate the technical solutions of the present application and not to limit it, and although the present application has been described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A method for preparing aramid surface grafting polymerization modified reinforced protective material, characterized in that: Comprising the following steps, S1 acid mixed solution preparation; With methyl triethoxysilane MTES as the precursor and anhydrous ethanol EtOH as the solvent, methyl triethoxysilane MTES is added to the mixed solution of hydrochloric acid HCl and anhydrous ethanol EtOH, and the mass ratio of the methyl triethoxysilane MTES, HCl, and EtOH is 1:1-2:1-2, to obtain an acid mixed solution; S2 diatomite DE acidification treatment, step S2 acidification treatment step, the acid mixed solution obtained in S1 is stirred at room temperature at a speed of 500 rpm for 12 h, then diatomite DE is placed in the acid mixed solution, and drying treatment is carried out at 60-80°C to obtain acidified diatomite DE; S3 preparation of CNTs based on acidified diatomite DE, step S3 includes, acidified diatomite DE is modified by 0.01~0.2 mol / L nickel nitrate, and then black solid powder CNTs is synthesized by chemical vapor deposition method in an inert gas atmosphere; S4 excessive matrix preparation; The CNTs prepared in S3 are acid modified, washed to neutral after ultrasonic dispersion, and an excessive matrix CNTs-OH is obtained; S5 preparation of ammonium polyphosphate modified material, step S5 method is, CNTs-OH is weighed and placed in 4-dimethylaminopyridine DMAP, polyacrylic acid PAA, and dimethylacetamide DMF interfacial grafting inducer, and the mass ratio is 1-2:1-3:1-3:1-3, so that carboxylated carbon nanotube CNTs-COOH is obtained, ammonium polyphosphate APP is dissolved in distilled water, and the mass ratio is 1:2-8, carboxylated carbon nanotube CNTs-COOH is placed in anhydrous ethanol, and the mass ratio is 1:2-8, and the two are mixed to obtain ammonium polyphosphate modified material APP@CNTs by solvent crystallization method; S6 melamine formaldehyde resin preparation; S7 preparation of core-shell microencapsulated ammonium polyphosphate modified material, step S7 includes, ammonium polyphosphate modified material APP@CNTs and melamine formaldehyde resin MFR are added to anhydrous ethanol EtOH solution in a proportion of 2-8:1, stirred uniformly, sulfuric acid is introduced to adjust pH=3-4, high temperature reaction and drying for 12 h, to obtain core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR; S8 fiber surface roughening treatment; The aramid fiber AF is immersed in the ethanol solution for 0.5 h, and the ethanol covers the fiber completely; S9 fiber interface modification treatment, step S9 includes, the fiber obtained in S8 is placed in a mixed solution of ethanol and silane coupling agent with a mass ratio of 8-12:1, and the mixed liquid is placed in a magnetic stirrer for 1 h; S10 composite fiber material preparation; The core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR prepared in S7 was placed in a medium solution, and the modified fiber prepared in S9 was placed in the core-shell microencapsulated ammonium polyphosphate modified material APP@CNTs-MFR suspension, and was ultrasonically dispersed at room temperature for 1 h, repeated for 3 times. The dipped fabric was passed through a mangle, and the experiment was repeated for 3 times. The treated fiber was dried in an oven at 90°C for 24 h to obtain the completed loaded composite fiber APP@CNTs-MFR / AF.

2. The method of claim 1, wherein: The acid modification in step S4 was performed by using concentrated sulfuric acid and concentrated nitric acid.

3. The method of claim 1, wherein: The method in step S6 was that melamine was dissolved in formaldehyde with a mass ratio of 1:2-8, and the pH was adjusted to 8-9 by using a sodium carbonate aqueous solution, and the mixture was heated in a water bath at 80-100°C with continuous stirring. After filtration, washing and drying, melamine formaldehyde resin MFR was obtained.

4. The method of claim 1, wherein: The medium solution in step S10 was mainly a mixture of ethanol and distilled water with a ratio of 1-2:1-2.

5. An aramid fiber surface grafting polymerization modified reinforced protective material prepared by the preparation method in any one of claims 1-4.

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