A composite material for helmets and a method for producing the same

Abstract

The present application belongs to the technical field of polymer composite materials, and particularly relates to a composite material for helmets and a preparation method thereof. The composite material for helmets comprises the following raw materials in parts by weight: epoxy resin 100 parts, carbon fiber woven cloth 50-60 parts, modifier 2-4 parts, isophorone diamine 13-15 parts, silane coupling agent 0.3-0.5 parts, and acetone 2-3.5 parts. The composite material is modified by using a modifier on the epoxy resin, wherein the multi-site active amine groups at both ends of the modifier molecules can form a good infiltration interface and a micro hydrogen bond network with the fiber surface and the resin matrix, and the propionate flexible chain segment toughening, the double-sided hindered amine antioxidant, and the multi-site amine group interface enhancement can jointly improve the mechanical properties of the composite material. After the helmet is made, the impact absorption performance of the helmet can be improved, and the structural stability of the shell under lateral load can be improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to a composite material for helmets and its preparation method. Background Technology

[0002] Epoxy resin-based composite materials with carbon fiber reinforcement have gained widespread application in high-end helmet manufacturing due to their high specific strength, high specific modulus, and excellent lightweight properties. This material system, molded through processes such as prepreg molding or vacuum-assisted resin infusion, can produce compact, form-fitting helmet shells, effectively meeting the dual requirements of weight reduction and strength in sports protection, military, and industrial safety scenarios. Compared to traditional thermoplastic helmets made of acrylonitrile-butadiene-styrene copolymer (ABS) and polycarbonate (PC), carbon fiber / epoxy composite helmets have significant advantages in ballistic penetration resistance, structural rigidity, and weather resistance, maintaining excellent load-bearing capacity while achieving weight reduction.

[0003] However, this composite material system still has significant performance shortcomings in practical helmet applications. On the one hand, the epoxy resin, after curing, forms a highly cross-linked rigid network structure with low elongation at break, making it a typical brittle material. When the helmet is impacted, this brittle matrix cannot effectively dissipate energy through its own plastic deformation, resulting in the impact energy being mainly absorbed by fiber breakage and interfacial debonding, leading to significantly low energy absorption efficiency. More seriously, this material exhibits catastrophic failure characteristics under dynamic impact, with numerous and severe cracks in the shell and a large number of cracks easily forming in the inner foam layer, posing a risk of secondary injury to the head. On the other hand, the significant anisotropy of carbon fiber composites makes them prone to excessive deformation under lateral pressure. Furthermore, the composite structure of carbon fiber and epoxy resin inherently suffers from weak interlaminar strength, making it susceptible to delamination or cracking in complex environments, thus limiting the stability of its lateral load-bearing capacity. Therefore, further research is needed on the impact absorption performance and lateral stiffness of composite materials for helmets. Summary of the Invention

[0004] The primary objective of this invention is to provide a composite material for helmets.

[0005] A second objective of this invention is to provide a method for preparing a composite material for helmets.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a composite material for helmets, comprising the following raw materials in parts by weight: 100 parts epoxy resin, 50-60 parts carbon fiber woven fabric, 2-4 parts modifier, 13-15 parts isophorone diamine, 0.3-0.5 parts silane coupling agent, and 2-3.5 parts acetone.

[0008] The preparation method of the modifier includes the following steps:

[0009] (1) Add 2,2,6,6-tetramethyl-4-piperidinol, 3-bromopropionic acid and p-toluenesulfonic acid to toluene and react at 110-115℃ for 4-6 h to obtain intermediate 1;

[0010] (2) Add intermediate 1 and anhydrous sodium sulfide to anhydrous ethanol, then add tetrabutylammonium bromide, and react at 70-80℃ for 4-5 h to obtain intermediate 2;

[0011] (3) Mix intermediate 2, acetonitrile, and tert-butanol, then add 1,1,1-trifluoroacetophenone, add hydrogen peroxide solution at 15-20℃, and react at 20-25℃ for 1.5-2h to obtain intermediate 3;

[0012] (4) Add intermediate 3, anhydrous potassium carbonate and potassium iodide to DMF, heat to 50-60℃ and then add DMF solution containing p-fluorobenzaldehyde, react at 70-80℃ for 8-10h to obtain intermediate 4.

[0013] (5) Add intermediate 4 and n-butylamine to anhydrous methanol and react at 60-65℃ for 4-5h; after the reaction, cool to 0-5℃, add sodium borohydride, and continue to react at 25-30℃ for 3-4h to obtain the modifier.

[0014] Preferably, in step (1), the ratio of the amount of 2,2,6,6-tetramethyl-4-piperidinol, 3-bromopropionic acid, p-toluenesulfonic acid, and toluene is 1 mol: 1.0-1.1 mol: 0.01-0.05 mol: 400-500 mL.

[0015] Preferably, in step (2), the ratio of intermediate 1, anhydrous sodium sulfide, anhydrous ethanol, and tetrabutylammonium bromide is 2mol: 1.0-1.1mol: 500-600mL: 0.02-0.05mol.

[0016] Preferably, in step (3), the ratio of intermediate 2, acetonitrile, tert-butanol, 1,1,1-trifluoroacetophenone, and hydrogen peroxide solution is 1 mol: 300-400 mL: 100-150 mL: 0.1-0.2 mol: 230-250 mL; and the concentration of hydrogen peroxide solution is 30 wt%.

[0017] Preferably, in step (4), the ratio of intermediate 3, anhydrous potassium carbonate, potassium iodide, DMF, and DMF solution containing p-fluorobenzaldehyde is 1 mol: 2.2-2.5 mol: 0.1-0.2 mol: 500-600 mL: 100 mL; and the ratio of p-fluorobenzaldehyde to DMF in the DMF solution containing p-fluorobenzaldehyde is 2.1-2.3 mol: 100 mL.

[0018] Preferably, in step (5), the ratio of intermediate 4, n-butylamine, anhydrous methanol, and sodium borohydride is 1 mol: 2.2-2.5 mol: 600-800 mL: 2.5-3.0 mol.

[0019] Preferably, the epoxy resin is a bisphenol A type epoxy resin.

[0020] Preferably, the silane coupling agent is KH-560.

[0021] This invention provides a method for preparing the aforementioned composite material for helmets, comprising the following steps:

[0022] (1) According to the raw material ratio, first mix the epoxy resin, modifier and silane coupling agent evenly, and then vacuum degas to obtain a modified epoxy resin mixture; then add isophorone diamine and acetone and mix evenly to obtain a modified epoxy resin liquid.

[0023] (2) The carbon fiber woven fabric is degummed and acidified to obtain pretreated carbon fiber woven fabric;

[0024] (3) The modified epoxy resin is coated on the surface of the pretreated carbon fiber woven fabric and cured to obtain a composite material for helmets.

[0025] Compared with the prior art, the main advantages of the present invention are as follows:

[0026] This invention provides a composite material for helmets. The composite material uses a modifier to modify epoxy resin. The modifier uses a thermally stable sulfone group as its core symmetry axis, bridging the hindered amine backbone via a propionate flexible segment, and constructs secondary amine active sites with highly efficient free radical scavenging capabilities at the ends using p-fluorobenzaldehyde and n-butylamine. During the composite material preparation process, the multi-site active amine groups at both ends of the modifier molecule can form a good wetting interface and microscopic hydrogen bond network with the fiber surface and resin matrix. Simultaneously, the propionate flexible segment toughens the composite, the hindered amine provides antioxidant protection, and the multi-site amine group interface enhances the composite material's mechanical properties.

[0027] The modifier of this invention improves the wettability of the resin matrix to carbon fibers and enhances the interlaminar shear strength of the composite material. When the composite material of this invention is used to manufacture helmets, under severe impact or stress concentration, the flexible segments improve the shell's ductility, and the transient dissociation and recombination of the intermolecular hydrogen bond network can help dissipate some of the impact energy. In conjunction with the plastic deformation of the flexible segments, the impact absorption performance of the helmet is improved. The enhanced interlaminar shear strength improves the structural stability of the shell under lateral loads and reduces the risk of delamination and cracking. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0029] Example 1

[0030] This embodiment provides a composite material for helmets, comprising the following raw materials in parts by weight: 100 parts of bisphenol A type epoxy resin (E-51), 55 parts of carbon fiber woven fabric (T700), 3 parts of modifier, 14 parts of isophorone diamine, 0.4 parts of silane coupling agent (KH-560), and 3 parts of acetone.

[0031] The preparation method of the modifier in this embodiment includes the following steps:

[0032] (1) 2,2,6,6-Tetramethyl-4-piperidinol, 3-bromopropionic acid, and p-toluenesulfonic acid were added to toluene, and the reaction system was heated to 115℃ and refluxed for 5 h; wherein, the molar ratio of 2,2,6,6-tetramethyl-4-piperidinol, 3-bromopropionic acid, p-toluenesulfonic acid, and toluene was 1 mol: 1.1 mol: 0.03 mol: 450 mL; after the reaction was completed, the reaction solution was cooled to 25℃, and 10 wt% sodium bicarbonate aqueous solution was added to adjust the pH of the system to 7.5. The mixture was allowed to stand and separated, the aqueous layer was extracted with toluene, and the organic layers were combined; the organic layers were washed successively with water and saturated brine, and dried with anhydrous sodium sulfate; the desiccant was removed by filtration, the filtrate was concentrated under reduced pressure to remove the solvent, and the residue was purified by column chromatography, and the eluent was removed under reduced pressure to obtain intermediate 1. Intermediate 1 1 HNMR: (C 12 H 22 BrNO2, 400MHz, DMSO-d6) δ: 1.22 (s, 12H), 1.51 (m, 2H), 1.76 (m, 2H), 2.0 (s, 1H), 2.75 (t, 2H), 3.69 (t, 2H), 5.22 (m, 1H). MS (ESI) m / z=291.08[M].

[0033] (2) Intermediate 1 and anhydrous sodium sulfide were added to anhydrous ethanol, followed by tetrabutylammonium bromide. The ratio of intermediate 1, anhydrous sodium sulfide, anhydrous ethanol, and tetrabutylammonium bromide was 2 mol: 1.1 mol: 550 mL: 0.03 mol. The reaction system was heated to 75 °C and refluxed for 4.5 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the generated sodium bromide inorganic salt solid was removed by filtration. The filter cake was washed with ethanol. The filtrate and washing liquid were combined, and the ethanol was removed by vacuum distillation. The residue was dissolved in dichloromethane, the organic layer was washed with water, and dried with anhydrous magnesium sulfate. The dichloromethane solvent was removed by vacuum distillation, and the crude product was recrystallized and dried to obtain intermediate 2. Intermediate 2 1 HNMR: (C 24 H 44 N2O4S, 400MHz, DMSO-d6) δ: 1.22 (s, 24H), 1.51 (m, 4H), 1.76 (m, 4H), 2.0 (s, 2H), 2.58 (t, 4H), 2.83 (t, 4H), 5.22 (m, 2H). MS (ESI) m / z=456.30[M].

[0034] (3) Intermediate 2, acetonitrile, and tert-butanol were mixed, and then 1,1,1-trifluoroacetophenone was added. A 30wt% hydrogen peroxide solution was added dropwise at 20°C. The ratio of intermediate 2, acetonitrile, tert-butanol, 1,1,1-trifluoroacetophenone, and hydrogen peroxide solution was 1 mol: 350 mL: 150 mL: 0.2 mol: 240 mL. After the addition was complete, the reaction was maintained at 25°C for 2 hours. After the reaction was complete, saturated sodium sulfite solution was added to neutralize the excess hydrogen peroxide. The solvent was removed under reduced pressure, and the residual aqueous phase was extracted with chloroform. The organic layers were combined, dried with anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The residual solid was recrystallized to obtain a fully symmetric sulfone intermediate 3. The intermediate 3... 1 HNMR: (C 24 H 44 N2O6S, 400MHz, DMSO-d6) δ: 1.22 (s, 24H), 1.51 (m, 4H), 1.76 (m, 4H), 2.0 (s, 2H), 2.63 (t, 4H), 3.80 (t, 4H), 5.22 (m, 2H). MS (ESI) m / z=489.30[M+H] + .

[0035] (4) Add intermediate 3, anhydrous potassium carbonate, and potassium iodide to anhydrous N,N-dimethylformamide (DMF). After heating to 55°C, add dropwise a DMF solution containing p-fluorobenzaldehyde. The ratio of intermediate 3, anhydrous potassium carbonate, potassium iodide, DMF, and the DMF solution containing p-fluorobenzaldehyde is 1 mol: 2.3 mol: 0.1 mol: 550 mL: 100 mL; the ratio of p-fluorobenzaldehyde to DMF in the DMF solution is 2.2 mol: 100 mL. After the addition is complete, heat the reaction system to 75°C and react for 9 h. After the reaction is complete, cool the reaction solution to room temperature and pour it into ice water to precipitate the solid. Filter, and wash the filter cake successively with water and cold ethanol. The crude product is purified by column chromatography, and after removing the eluent under reduced pressure, the di-terminated aldehyde intermediate 4 is obtained. The intermediate 4... 1 HNMR: (C 38 H 52 N2O8S, 400MHz, DMSO-d6) δ: 1.35 (s, 24H), 1.51 (m, 4H), 1.76 (m, 4H), 2.63 (t, 4H), 3.80 (t, 4H), 5.22 (m, 2H), 7.01 (m, 4H), 7.14 (m, 4H), 9.89 (s, 2H). MS (ESI) m / z=697.35[M+H] + .

[0036] (5) Add intermediate 4 and n-butylamine to anhydrous methanol. Add molecular sieve as a dehydrating agent and reflux at 65°C for 4.5 h. After the reaction, cool the system to 0°C, add sodium borohydride as a reducing agent, and control the addition rate so that the system temperature does not exceed 10°C. After the addition is complete, continue the reaction at 30°C for 3.5 h. The ratio of intermediate 4, n-butylamine, anhydrous methanol, and sodium borohydride is 1 mol: 2.3 mol: 700 mL: 2.8 mol. After the reaction, add 10 wt% hydrochloric acid solution dropwise to quench excess sodium borohydride and adjust the pH to 2.5. After stirring for 0.5 h, adjust the pH to 9.5 with 10 wt% sodium hydroxide aqueous solution. Remove methanol under reduced pressure, and extract the residue with ethyl acetate. Combine the organic layers, wash with saturated brine, and dry with anhydrous sodium sulfate. Remove ethyl acetate under reduced pressure, recrystallize the residue, and dry under vacuum to obtain the modifier. 1 HNMR: (C 46 H 74N4O6S, 400MHz, DMSO-d6) δ: 0.89 (t, 6H), 1.30-1.38 (m, 32H), 1.51 (m, 4H), 1.76 (m, 4H), 2.53 (t, 4H), 2.63 (t, 4H), 3.64 (s, 4H), 3.80 (t, 4H), 4.16 (s, 2H), 5.22 (m, 2H), 6.71 (m, 4H), 7.10 (m, 4H). MS (ESI) m / z=811.54[M+H] + .

[0037]

[0038] The preparation method of the composite material for helmets in this embodiment includes the following steps:

[0039] (1) According to the raw material ratio, first mix the bisphenol A type epoxy resin, modifier and silane coupling agent evenly, and then vacuum degas to obtain a modified epoxy resin mixture; then add isophorone diamine and acetone and mix evenly to obtain a modified epoxy resin liquid.

[0040] (2) The carbon fiber woven fabric is degummed and acidified to obtain pretreated carbon fiber woven fabric. The specific method is as follows: the carbon fiber woven fabric is immersed in acetone and ultrasonically treated for 2 hours, then placed in 30wt% nitric acid solution and heated and refluxed at 60℃ for 4 hours. After washing and drying, the pretreated carbon fiber woven fabric is obtained.

[0041] (3) The modified epoxy resin liquid is uniformly coated on the surface of the pretreated carbon fiber woven fabric by a coating roller (the amount of coating is controlled, the epoxy resin content is 40wt%, and the remainder is carbon fiber) to obtain a prepreg, and after curing, a composite material for helmets is obtained.

[0042] Example 2

[0043] This embodiment provides a composite material for helmets, comprising the following raw materials in parts by weight: 100 parts of bisphenol A type epoxy resin (E-51), 60 parts of carbon fiber woven fabric (T700), 4 parts of modifier, 15 parts of isophorone diamine, 0.5 parts of silane coupling agent (KH-560), and 3.5 parts of acetone.

[0044] The preparation method of the modifier in this embodiment includes the following steps:

[0045] (1) 2,2,6,6-Tetramethyl-4-piperidinol, 3-bromopropionic acid, and p-toluenesulfonic acid were added to toluene, and the reaction system was heated to 115℃ and refluxed for 4 hours; wherein, the ratio of 2,2,6,6-tetramethyl-4-piperidinol, 3-bromopropionic acid, p-toluenesulfonic acid, and toluene was 1 mol: 1.1 mol: 0.05 mol: 500 mL; after the reaction was completed, the reaction solution was cooled to 25℃, and 10 wt% sodium bicarbonate aqueous solution was added to adjust the pH of the system to 7.5. The mixture was allowed to stand and separated, the aqueous layer was extracted with toluene, and the organic layers were combined; the organic layers were washed successively with water and saturated brine, and dried with anhydrous sodium sulfate; the desiccant was removed by filtration, the filtrate was concentrated under reduced pressure to remove the solvent, and the residue was purified by column chromatography, and the eluent was removed under reduced pressure to obtain intermediate 1. Intermediate 1 1 HNMR is the same as in Example 1.

[0046] (2) Intermediate 1 and anhydrous sodium sulfide were added to anhydrous ethanol, followed by tetrabutylammonium bromide. The ratio of intermediate 1, anhydrous sodium sulfide, anhydrous ethanol, and tetrabutylammonium bromide was 2 mol: 1.1 mol: 600 mL: 0.05 mol. The reaction system was heated to 80 °C and refluxed for 4 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the generated sodium bromide inorganic salt solid was removed by filtration. The filter cake was washed with ethanol. The filtrate and washing liquid were combined, and the ethanol was removed by vacuum distillation. The residue was dissolved in dichloromethane, the organic layer was washed with water, and dried with anhydrous magnesium sulfate. The dichloromethane solvent was removed by vacuum distillation, and the crude product was recrystallized and dried to obtain intermediate 2. Intermediate 2 1 HNMR is the same as in Example 1.

[0047] (3) Intermediate 2, acetonitrile, and tert-butanol were mixed, and then 1,1,1-trifluoroacetophenone was added. A 30wt% hydrogen peroxide solution was added dropwise at 20°C. The ratio of intermediate 2, acetonitrile, tert-butanol, 1,1,1-trifluoroacetophenone, and hydrogen peroxide solution was 1 mol: 400 mL: 150 mL: 0.2 mol: 250 mL. After the addition was complete, the reaction was maintained at 25°C for 1.5 h. After the reaction was complete, saturated sodium sulfite solution was added to neutralize the excess hydrogen peroxide. The solvent was removed under reduced pressure, and the residual aqueous phase was extracted with chloroform. The organic layers were combined, dried with anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The residual solid was recrystallized to obtain a fully symmetric sulfone intermediate 3. The intermediate 3... 1 HNMR is the same as in Example 1.

[0048] (4) Add intermediate 3, anhydrous potassium carbonate, and potassium iodide to anhydrous N,N-dimethylformamide (DMF). After heating to 60°C, add dropwise a DMF solution containing p-fluorobenzaldehyde. The ratio of intermediate 3, anhydrous potassium carbonate, potassium iodide, DMF, and the DMF solution containing p-fluorobenzaldehyde is 1 mol: 2.5 mol: 0.2 mol: 600 mL: 100 mL; the ratio of p-fluorobenzaldehyde to DMF in the DMF solution is 2.3 mol: 100 mL. After the addition is complete, heat the reaction system to 80°C and react for 8 hours. After the reaction is complete, cool the reaction solution to room temperature and pour it into ice water to precipitate the solid. Filter, and wash the filter cake successively with water and cold ethanol. Purify the crude product by column chromatography, remove the eluent under reduced pressure, and obtain intermediate 4 with a di-terminated aldehyde group. The intermediate 4... 1 HNMR is the same as in Example 1.

[0049] (5) Add intermediate 4 and n-butylamine to anhydrous methanol. Add molecular sieve as a dehydrating agent and reflux at 65°C for 4 h. After the reaction, cool the system to 5°C, add sodium borohydride as a reducing agent, and control the addition rate so that the system temperature does not exceed 10°C. After the addition is complete, continue the reaction at 30°C for 3 h. The ratio of intermediate 4, n-butylamine, anhydrous methanol, and sodium borohydride is 1 mol: 2.5 mol: 800 mL: 3.0 mol. After the reaction, add 10 wt% hydrochloric acid solution to quench excess sodium borohydride and adjust the pH to 2.5. After stirring for 0.5 h, adjust the pH to 9.5 with 10 wt% sodium hydroxide aqueous solution. Remove methanol under reduced pressure, and extract the residue with ethyl acetate. Combine the organic layers, wash with saturated brine, and dry with anhydrous sodium sulfate. Remove ethyl acetate under reduced pressure, recrystallize the residue, and dry under vacuum to obtain the modifier. 1 HNMR is the same as in Example 1.

[0050] The preparation method of the composite material for the helmet in this embodiment is the same as that in Embodiment 1.

[0051] Example 3

[0052] This embodiment provides a composite material for helmets, comprising the following raw materials in parts by weight: 100 parts of bisphenol A type epoxy resin (E-51), 50 parts of carbon fiber woven fabric (T700), 2 parts of modifier, 13 parts of isophorone diamine, 0.3 parts of silane coupling agent (KH-560), and 2 parts of acetone.

[0053] The preparation method of the modifier in this embodiment includes the following steps:

[0054] (1) 2,2,6,6-Tetramethyl-4-piperidinol, 3-bromopropionic acid, and p-toluenesulfonic acid were added to toluene, and the reaction system was heated to 110℃ and refluxed for 6 h; wherein, the ratio of 2,2,6,6-tetramethyl-4-piperidinol, 3-bromopropionic acid, p-toluenesulfonic acid, and toluene was 1 mol: 1.0 mol: 0.01 mol: 400 mL; after the reaction was completed, the reaction solution was cooled to 25℃, and 10 wt% sodium bicarbonate aqueous solution was added to adjust the pH of the system to 7.5. The mixture was allowed to stand and separated, the aqueous layer was extracted with toluene, and the organic layers were combined; the organic layers were washed successively with water and saturated brine, and dried with anhydrous sodium sulfate; the desiccant was removed by filtration, the filtrate was concentrated under reduced pressure to remove the solvent, and the residue was purified by column chromatography, and the eluent was removed under reduced pressure to obtain intermediate 1. Intermediate 1 1 HNMR is the same as in Example 1.

[0055] (2) Intermediate 1 and anhydrous sodium sulfide were added to anhydrous ethanol, followed by tetrabutylammonium bromide. The ratio of intermediate 1, anhydrous sodium sulfide, anhydrous ethanol, and tetrabutylammonium bromide was 2 mol: 1.0 mol: 500 mL: 0.02 mol. The reaction system was heated to 70 °C and refluxed for 5 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the generated sodium bromide inorganic salt solid was removed by filtration. The filter cake was washed with ethanol. The filtrate and washing liquid were combined, and the ethanol was removed by vacuum distillation. The residue was dissolved in dichloromethane, the organic layer was washed with water, and dried with anhydrous magnesium sulfate. The dichloromethane solvent was removed by vacuum distillation, and the crude product was recrystallized and dried to obtain intermediate 2. Intermediate 2 1 HNMR is the same as in Example 1.

[0056] (3) Intermediate 2, acetonitrile, and tert-butanol were mixed, and then 1,1,1-trifluoroacetophenone was added. A 30wt% hydrogen peroxide solution was added dropwise at 15°C. The ratio of intermediate 2, acetonitrile, tert-butanol, 1,1,1-trifluoroacetophenone, and hydrogen peroxide solution was 1 mol: 300 mL: 100 mL: 0.1 mol: 230 mL. After the addition was complete, the reaction was maintained at 20°C for 2 hours. After the reaction was complete, saturated sodium sulfite solution was added to neutralize the excess hydrogen peroxide. The solvent was removed under reduced pressure, and the residual aqueous phase was extracted with chloroform. The organic layers were combined, dried with anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The residual solid was recrystallized to obtain a fully symmetric sulfone intermediate 3. The intermediate 3... 1 HNMR is the same as in Example 1.

[0057] (4) Add intermediate 3, anhydrous potassium carbonate, and potassium iodide to anhydrous N,N-dimethylformamide (DMF). After heating to 50°C, add dropwise a DMF solution containing p-fluorobenzaldehyde. The ratio of intermediate 3, anhydrous potassium carbonate, potassium iodide, DMF, and the DMF solution containing p-fluorobenzaldehyde is 1 mol: 2.2 mol: 0.1 mol: 500 mL: 100 mL; the ratio of p-fluorobenzaldehyde to DMF in the DMF solution is 2.1 mol: 100 mL. After the addition is complete, heat the reaction system to 70°C and react for 10 h. After the reaction is complete, cool the reaction solution to room temperature and pour it into ice water to precipitate the solid. Filter, and wash the filter cake successively with water and cold ethanol. The crude product is purified by column chromatography, and after removing the eluent under reduced pressure, the di-terminated aldehyde intermediate 4 is obtained. The intermediate 4... 1 HNMR is the same as in Example 1.

[0058] (5) Add intermediate 4 and n-butylamine to anhydrous methanol. Add molecular sieve as a dehydrating agent and reflux at 60°C for 5 h. After the reaction, cool the system to 0°C, add sodium borohydride as a reducing agent, and control the addition rate so that the system temperature does not exceed 10°C. After the addition is complete, continue the reaction at 25°C for 4 h. The ratio of intermediate 4, n-butylamine, anhydrous methanol, and sodium borohydride is 1 mol: 2.2 mol: 600 mL: 2.5 mol. After the reaction, add 10 wt% hydrochloric acid solution to quench excess sodium borohydride and adjust the pH to 2.5. After stirring for 0.5 h, adjust the pH to 9.5 with 10 wt% sodium hydroxide aqueous solution. Remove methanol under reduced pressure, and extract the residue with ethyl acetate. Combine the organic layers, wash with saturated brine, and dry with anhydrous sodium sulfate. Remove ethyl acetate under reduced pressure, recrystallize the residue, and dry under vacuum to obtain the modifier. 1 HNMR is the same as in Example 1.

[0059] The preparation method of the composite material for the helmet in this embodiment is the same as that in Embodiment 1.

[0060] Comparative Example 1

[0061] This comparative example provides a composite material for helmets. The difference from Example 1 is that the modifier in the raw material of the helmet composite material is replaced with intermediate 4 (prepared in Example 1), while the rest is the same as Example 1.

[0062] Comparative Example 2

[0063] This comparative example provides a composite material for helmets. The difference from Example 1 is that the modifier in the raw material of the helmet composite material is replaced with intermediate 2 (prepared in Example 1), while the rest is the same as Example 1.

[0064] Test case

[0065] According to relevant standards, the composite materials obtained in Examples 1-3 and Comparative Examples 1-2 of this invention were made into corresponding test samples, and the mechanical properties of the composite materials were tested. The tensile strength of the test samples was determined with reference to GB / T1447-2005 "Test Method for Tensile Properties of Fiber Reinforced Plastics"; the interlaminar shear strength of the test samples was determined with reference to GB / T1450.1-2005 "Test Method for Interlaminar Shear Strength of Fiber Reinforced Plastics".

[0066] The composite materials obtained in Examples 1-3 and Comparative Examples 1-2 of this invention were used to manufacture helmet shells. The preparation method was as follows: the composite materials (prepregs before curing) of each group were laid up in a mold using a negative mold, followed by vacuuming, curing, cooling, and demolding to obtain the helmet shell. The impact absorption performance (impact force) and lateral stiffness of the helmet shell were measured according to GB / T2812-2024 "General Test Methods for Head Protection". The results are shown in Table 1.

[0067] Table 1

[0068] Tensile strength (MPa) 1697 1673 1664 1475 1342 Interlaminar shear strength (MPa) 85 82 81 74 66 Impact force (N) 3650 3750 3800 4150 4300 Lateral stiffness (maximum deformation in mm) 19 22 23 29 31 Lateral stiffness (residual deformation mm) 3 5 6 9 11

[0069] As shown in Table 1, the mechanical properties of the composite materials obtained in Examples 1-3 of this invention are superior to those in Comparative Examples 1-2. The impact absorption performance and lateral stiffness of the helmet shells made from the composite materials obtained in Examples 1-3 both meet the standard requirements and are even better than those in Comparative Examples 1-2. The reason for this is that the composite materials use a modifier to modify the epoxy resin. The multi-site active amine groups at both ends of the modifier molecule can form a good wetting interface and microscopic hydrogen bond network with the fiber surface and resin matrix. At the same time, the propionate ester flexible chain segment toughens, the double-sided hindered amine resists oxidation, and the multi-site amine group interface is strengthened, all of which jointly improve the mechanical properties of the composite material. After the helmet is made, the transient dissociation and recombination of the intermolecular hydrogen bond network can help dissipate some of the impact energy, and the plastic deformation of the flexible chain segment can improve the impact absorption performance of the helmet. The enhancement of interlaminar shear strength improves the structural stability of the shell under lateral load and reduces the risk of delamination and cracking.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A composite material for helmets, characterized in that, The raw materials include the following parts by weight: 100 parts epoxy resin, 50-60 parts carbon fiber woven fabric, 2-4 parts modifier, 13-15 parts isophorone diamine, 0.3-0.5 parts silane coupling agent, and 2-3.5 parts acetone. The preparation method of the modifier includes the following steps: (1) Add 2,2,6,6-tetramethyl-4-piperidinol, 3-bromopropionic acid and p-toluenesulfonic acid to toluene and react at 110-115℃ for 4-6 h to obtain intermediate 1; (2) Add intermediate 1 and anhydrous sodium sulfide to anhydrous ethanol, then add tetrabutylammonium bromide, and react at 70-80℃ for 4-5 h to obtain intermediate 2; (3) Mix intermediate 2, acetonitrile, and tert-butanol, then add 1,1,1-trifluoroacetophenone, add hydrogen peroxide solution at 15-20℃, and react at 20-25℃ for 1.5-2h to obtain intermediate 3; (4) Add intermediate 3, anhydrous potassium carbonate and potassium iodide to DMF, heat to 50-60℃ and then add DMF solution containing p-fluorobenzaldehyde, react at 70-80℃ for 8-10h to obtain intermediate 4. (5) Add intermediate 4 and n-butylamine to anhydrous methanol and react at 60-65℃ for 4-5h; after the reaction, cool to 0-5℃, add sodium borohydride, and continue to react at 25-30℃ for 3-4h to obtain the modifier.

2. The composite material for helmets according to claim 1, characterized in that, In step (1), the ratio of 2,2,6,6-tetramethyl-4-piperidinol, 3-bromopropionic acid, p-toluenesulfonic acid, and toluene is 1 mol: 1.0-1.1 mol: 0.01-0.05 mol: 400-500 mL.

3. The composite material for helmets according to claim 1, characterized in that, In step (2), the ratio of intermediate 1, anhydrous sodium sulfide, anhydrous ethanol and tetrabutylammonium bromide is 2mol: 1.0-1.1mol: 500-600mL: 0.02-0.05mol.

4. The composite material for helmets according to claim 1, characterized in that, In step (3), the ratio of intermediate 2, acetonitrile, tert-butanol, 1,1,1-trifluoroacetophenone, and hydrogen peroxide solution is 1 mol: 300-400 mL: 100-150 mL: 0.1-0.2 mol: 230-250 mL; the concentration of hydrogen peroxide solution is 30 wt%.

5. The composite material for helmets according to claim 1, characterized in that, In step (4), the ratio of intermediate 3, anhydrous potassium carbonate, potassium iodide, DMF, and DMF solution containing p-fluorobenzaldehyde is 1 mol: 2.2-2.5 mol: 0.1-0.2 mol: 500-600 mL: 100 mL; the ratio of p-fluorobenzaldehyde to DMF in the DMF solution containing p-fluorobenzaldehyde is 2.1-2.3 mol: 100 mL.

6. The composite material for helmets according to claim 1, characterized in that, In step (5), the ratio of intermediate 4, n-butylamine, anhydrous methanol, and sodium borohydride is 1 mol: 2.2-2.5 mol: 600-800 mL: 2.5-3.0 mol.

7. The composite material for helmets according to claim 1, characterized in that, The epoxy resin is a bisphenol A type epoxy resin.

8. The composite material for helmets according to claim 1, characterized in that, The silane coupling agent is KH-560.

9. The method for preparing the composite material for helmets according to any one of claims 1-8, characterized in that, Includes the following steps: (1) According to the raw material ratio, first mix the epoxy resin, modifier and silane coupling agent evenly, and then vacuum degas to obtain a modified epoxy resin mixture; then add isophorone diamine and acetone and mix evenly to obtain a modified epoxy resin liquid. (2) The carbon fiber woven fabric is degummed and acidified to obtain pretreated carbon fiber woven fabric; (3) The modified epoxy resin is coated on the surface of the pretreated carbon fiber woven fabric and cured to obtain a composite material for helmets.

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