Chin protection pad for sports helmet

Abstract

The invention discloses a chin protection liner for a sports helmet, and relates to the technical field of sports helmets, the chin protection liner comprises a honeycomb structure area and a wave structure area; the liner is made of a composite material containing polyformaldehyde, a thermoplastic polyurethane elastomer, a nucleating agent, ionic liquid and an epoxy compound; the ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate, and the ionic liquid is an ionic liquid; the epoxy compound comprises 1, 2-epoxy hexadecane and 9-octylheptadecane epoxy, and the epoxy compound comprises 1, 2-epoxy hexadecane and 9-octylheptadecane epoxy; by introducing the ionic liquid and the specific epoxy compound, toughening modification of the pad material is realized, the impact toughness and ductility of the material are improved, and good rigid-tough balance is maintained, so that the chin protection pad for the sports helmet can provide lasting and effective protection in a complex and changeable impact environment, and the service life of the chin protection pad is prolonged. Meanwhile, the requirements for temperature change resistance and aging resistance are met, and the material is widely applied to the field of various sports protectors.

Description

Technical Field

[0001] The present invention relates to the technical field of sports helmets, in particular to a chin protection pad for sports helmets. Background Art

[0002] In the field of sports helmet technology, the chin guard pad is a key safety component, and its performance directly affects the overall protective effect of the helmet and the wearer's comfort. The chin guard pads of traditional sports helmets are often made of a single material. The preparation process suffers from uneven dispersion of the nucleating agent and easy agglomeration. Single materials also have problems such as high hardness, insufficient cushioning performance, and easy aging and brittleness, making it difficult to provide long-lasting and effective protection in complex and changing impact environments. Especially during high-intensity exercise or accidental impacts, traditional pads often fail to fully absorb and disperse impact energy, resulting in damage to the wearer's chin and facial area.

[0003] Furthermore, traditional materials tend to become brittle at low temperatures and are susceptible to hydrolysis and aging in hot and humid conditions, further limiting their application and lifespan. Therefore, developing a chin protector for sports helmets that combines high impact toughness, good ductility, resistance to temperature changes, and resistance to aging has become a pressing technical challenge in the field of sports safety equipment. Summary of the Invention

[0004] The embodiments of the present application provide a chin protection pad for a sports helmet, thereby solving the technical problems in the prior art of insufficient impact toughness, poor ductility, and poor temperature change resistance and aging resistance of the padding material. By introducing ionic liquids and specific epoxy compounds, the padding material is toughened and modified, the impact toughness and ductility of the material are improved, and a good balance of rigidity and toughness is maintained, so that the chin protection pad for a sports helmet can provide long-lasting and effective protection in complex and changeable impact environments, while meeting the requirements of temperature change resistance and aging resistance, and is widely applicable to various sports protective gear fields.

[0005] An embodiment of the present application provides a chin protection pad for a sports helmet, comprising a honeycomb structure region and a wave structure region; the pad is made of a composite material comprising polyformaldehyde, a thermoplastic polyurethane elastomer, a nucleating agent, an ionic liquid and an epoxy compound; the ionic liquid is 1-butyl-3-methylimidazole hexafluorophosphate; and the epoxy compound comprises 1,2-epoxyhexadecane and 9-octylheptadecane epoxy.

[0006] Furthermore, the added amount of the ionic liquid is 0.3-0.8 parts by weight, and the added amount of 1,2-epoxyhexadecane is 0.8-1.8 parts by weight.

[0007] Furthermore, the mass ratio of the 1,2-epoxyhexadecane to the 9-octylheptadecane epoxy is 1:1.4.

[0008] Furthermore, the nucleating agent is montmorillonite, and the addition amount is 0.8-1.5 parts by weight; the montmorillonite is pre-treated by intercalation of ionic liquid and epoxy compound.

[0009] Furthermore, the honeycomb structure area is printed using a hexagonal spiral filling algorithm, and the wave structure area is printed using a concentric circle topology scanning path.

[0010] A method for preparing a chin protection liner for a sports helmet comprises the following steps: step 1, mixing montmorillonite, 1-butyl-3-methylimidazolium hexafluorophosphate, 1,2-epoxyhexadecane and 9-octylheptadecane epoxy at 55-60°C for 40 minutes to form a pre-intercalation composite; step 2, mixing the pre-intercalation composite with polyether polyol, adding diphenylmethane diisocyanate, and reacting at 80-85°C to obtain a prepolymer; step 3, blending the prepolymer with a polyoxymethylene melt in a twin-screw extruder, and granulating and drying to obtain composite material particles.

[0011] Furthermore, the method further includes the following steps: forming the composite material particles by 3D printing; the printing parameters include: nozzle temperature 200-205°C, hot bed temperature 100-105°C, honeycomb area layer thickness 0.15mm, and wave area layer thickness 0.20mm; after printing, gradient cooling treatment is performed in sequence: 120°C for 30 minutes, 100°C for 60 minutes, and 80°C for 30 minutes.

[0012] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0013] By introducing ionic liquids and epoxy compounds, a breakthrough improvement in the toughening modification of gasket materials is achieved; ionic liquids can produce an intercalation and exfoliation effect on nucleating agents. The cations in the ionic liquids are embedded in the montmorillonite layers through electrostatic adsorption, and the anions produce Coulomb repulsion, which significantly expands the interlayer spacing, destroys the stacking structure of the montmorillonite layers, and forms thermodynamically stable exfoliated monodisperse nanosheets; the defect of excessive POM spherulites caused by nucleating agent agglomeration is solved, and the optimized uniform dispersion system refines the spherulites, thereby improving the uniformity of stress transfer. In addition, the ionic liquid forms a solvation layer in the polyol phase, which significantly reduces the shear viscosity of the prepolymer by reducing the melt viscosity and interfacial energy, ensuring the continuity and interfacial compatibility of the TPU network in the subsequent blending process, and suppressing the stress concentration crack source caused by local phase separation;

[0014] The epoxy compound 1,2-epoxyhexadecane is activated by the ionic liquid and the ring is opened to form a zwitterionic structure containing hydroxyl groups. The newly generated hydroxyl groups directly compensate for the active sites of the chain extender consumed by the ionic liquid, narrowing the molecular weight distribution width of TPU and restoring the extension energy absorption capacity of the polymer chain. In addition, the C 16The long-chain alkyl group acts as a molecular bridge, with one end anchored on the montmorillonite surface and the other end embedded in the amorphous region of POM, forming a physical entanglement network, thus avoiding the problem of rigidity loss in traditional toughening.

[0015] By introducing the epoxy compound 9-octylhexadecane epoxy with a specific branched structure, a synergistic effect is formed with the original 1,2-epoxyhexadecane and ionic liquid. Based on the triple effects of topological anchoring enhancement, free volume regulation, and ion and branch chain synergistic barrier, the problems of low-temperature impact failure and damp-heat aging performance attenuation of the material are solved, while the fatigue resistance is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a physical diagram of the honeycomb structure area of ​​the chin protection pad for the sports helmet of the present invention;

[0017] Figure 2 This is a real picture of the wave structure area of ​​the chin protection pad for the sports helmet of the present invention. DETAILED DESCRIPTION

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this invention pertains; the terms used in the specification of this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the related listed items. Example 1: A chin protector pad for a sports helmet is made from the following raw materials in parts by weight:

[0019] Polyol: 60 parts of polyether polyol (Mn=2000);

[0020] Nucleating agent: 1.2 parts of nano-montmorillonite;

[0021] Isocyanate: 45 parts of 4,4'-diphenylmethane diisocyanate (MDI);

[0022] Polyoxymethylene: 85 parts;

[0023] Main antioxidant: 0.3 parts of pentaerythritol tetrakis[β-(3,5-tert-butyl-4-hydroxyphenyl)propionate]; auxiliary antioxidant: 0.3 parts of didodecanol ester;

[0024] Formaldehyde absorbent: 0.5 parts of dicyandiamide;

[0025] Lubricant: 0.6 parts of polyethylene wax;

[0026] Chain extender: 5 parts of 1,4-butanediol;

[0027] Ionic liquid: [BMIM][PF6] 0.3-0.8 parts;

[0028] Epoxy compound: 0.8-1.8 parts of 1,2-epoxyhexadecane;

[0029] The preparation method of the chin protection pad for a sports helmet specifically comprises the following steps:

[0030] S1. Preparation of chin protection padding material for sports helmets;

[0031] S11. Weigh the above raw materials in parts by weight;

[0032] S12. Montmorillonite pre-intercalation treatment;

[0033] Add nano-montmorillonite, [BMIM][PF6], and 1,2-epoxyhexadecane into a high-speed mixer and mix at 800 rpm for 15 min at 60±2°C to allow the ionic liquid to penetrate into the interlayers of the montmorillonite.

[0034] The temperature was raised to 60°C and kept for 30 minutes to generate an expanded montmorillonite composite.

[0035] The product should be sealed and stored until use to prevent moisture absorption;

[0036] S13. Preparation of prepolymer;

[0037] mixing a polyether polyol with an expanded montmorillonite composite;

[0038] Stir at low speed (500 rpm) at 40°C for 10 min to allow the polyol to encapsulate the complex;

[0039] MDI was added and the mixture was reacted at 85°C for 40 min under nitrogen protection to generate a TPU prepolymer containing intercalated montmorillonite.

[0040] The NCO content of the prepolymer was detected to be 8.2±0.3%.

[0041] S14.POM melt preparation;

[0042] Put polyoxymethylene, primary antioxidant, secondary antioxidant, dicyandiamide, polyethylene wax and 1,4-butanediol into a twin-screw extruder;

[0043] Temperature gradient setting: 110℃, 150℃, 170℃, 180℃, 190℃, 200℃, 210℃ (machine head);

[0044] The main machine rotates at 200 rpm and extrude into a uniform melt (residence time ≤ 3 min);

[0045] S15. In situ blending reaction;

[0046] The TPU prepolymer and POM melt were injected into the co-rotating twin-screw extruder at a volume ratio of 1:2.5;

[0047] Temperature setting seven-zone gradient: 190℃, 200℃, 205℃, 205℃, 195℃, 180℃, 100℃ (head);

[0048] The main engine speed is 220rpm, and the material stays for 90 seconds;

[0049] The melt was cooled in a water tank and pelletized, and then dried with hot air at 80°C for 4 hours to obtain TPU toughened POM particles.

[0050] S2. Preparation of chin protection pads for sports helmets, such as Figure 1 and Figure 2 As shown, Figure 1 It is a honeycomb structure area, with a black mesh structure and rectangular slots. Figure 2 It is a wave structure area with arc-shaped hollow rib structure;

[0051] S21: Material pretreatment and wire preparation;

[0052] Place the TPU toughened POM particles in a vacuum drying oven at 80°C for 6 hours, ensuring that the moisture content is ≤ 0.03% to avoid printing bubbles;

[0053] The wires were prepared using a single-screw extruder with a diameter of 1.75 ± 0.03 mm;

[0054] Temperature zones: 165°C for feeding, 175°C for melting, 185°C for homogenization, 190°C for compression, and 185°C for setting;

[0055] The winding tension is 25N, and there are no scratches, bubbles or diameter fluctuations on the wire surface;

[0056] S22: Printing device (EOS P396) and parameter configuration;

[0057] Replace the hardened stainless steel nozzle with a diameter of 0.4 mm to withstand the hydrolysis products of ionic liquids;

[0058] The hot bed is equipped with a constant temperature system with an accuracy of ±2°C. The wave structure area is maintained at 105°C and the honeycomb structure area is 100°C.

[0059] A sealed drying cabin is added to the wire conveying system;

[0060] The specific printing parameters are:

[0061] Nozzle temperature: 205°C in the wave structure area, 200°C in the honeycomb structure area;

[0062] Printing speed: 50mm / s for wave structure area, arc continuous path, 35mm / s for spiral filling in honeycomb structure area;

[0063] Layer thickness: 0.20mm for the main body of the wave structure area, 0.15mm for the thin wall of the honeycomb structure area;

[0064] Filling strategy:

[0065] The honeycomb unit uses a hexagonal spiral algorithm with a wall thickness of 0.5mm;

[0066] The wavy surface is scanned using concentric circle topology with a spacing of 0.3 mm;

[0067] S23: Layered printing implementation;

[0068] (1) First layer adhesion strengthening:

[0069] Apply polyvinyl alcohol adhesive layer at 5% concentration on hot bed at 105℃;

[0070] The first layer is extruded at 120% flow rate and low speed of 25 mm / s;

[0071] (2) Printing of wave structure area:

[0072] The arc line of the arched area is continuously extruded, and the breakpoint interval is less than 0.2mm;

[0073] The thickness of the load-bearing ribs is greater than 1.2mm, and the filling rate is increased to 35%;

[0074] (3) Honeycomb structure area printing:

[0075] Thin walls implement 0.03mm pre-offset compensation to expand outward to prevent shrinkage and deformation;

[0076] After completing 3 layers, pause for 60 seconds to allow the POM to semi-crystallize and solidify;

[0077] Add soluble support to the rectangular groove in the lower right corner to prevent the overhang from collapsing;

[0078] S24: Post-processing

[0079] In-situ stress relief:

[0080] After printing, keep the hot bed at 100℃ for 20 minutes;

[0081] Gradient cooling: 120°C (30 min), 100°C (60 min), 80°C (30 min);

[0082] Surface functionalization treatment:

[0083] Dichloromethane vapor polishing (40°C, 5 seconds) to make the surface roughness Ra ≤ 1.2 μm;

[0084] The residual support material is removed from the inner wall of the honeycomb with an ultra-fine nylon brush (Φ0.3 mm) to obtain the chin protection pad.

[0085] Quality verification and performance test: experiments were conducted on chin protective pads prepared according to the technical solutions of the above embodiments, and the specific parameters are shown in Table 1 and Table 2:

[0086] Table 1. Base formula (parts by weight)

[0087]

[0088]

[0089] Table 2. Ionic liquid and epoxy compound (parts by weight)

[0090] Group <![CDATA[[BMIM][PF6](份)]]> 1,2-Epoxyhexadecane (parts) Comparative Example 1 0 0 Comparative Example 2 0.5 0 Comparative Example 3 0 1.2 Experimental Group 1 0.3 0.8 Experimental Group 2 0.5 1.2 Experimental Group 3 0.8 1.8

[0091] Performance testing, the detection standard is as follows:

[0092] Notched impact strength: determined according to ASTM D6110;

[0093] Tensile strength and elongation at break: determined according to ASTM D638;

[0094] Spherulite size: determined according to ISO 11357-3;

[0095] Heat distortion temperature: determined according to ASTM D648;

[0096] Helmet pad applicability: determined according to EN 1078;

[0097] The performance test results are shown in Table 3:

[0098] Table 3

[0099]

[0100]

[0101] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0102] By introducing ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6]) and epoxy compound (1,2-epoxyhexadecane), a breakthrough improvement in toughening modification of pad materials is achieved;

[0103] Ionic liquids can produce an intercalation and exfoliation effect on nucleating agents. The cations in the ionic liquid are embedded in the montmorillonite interlayers through electrostatic adsorption, and the anions produce Coulomb repulsion, which significantly expands the interlayer spacing, destroys the stacking structure of the montmorillonite layers, and forms thermodynamically stable exfoliated monodisperse nanosheets. This solves the problem of excessive POM spherulite size caused by nucleating agent agglomeration. The optimized uniform dispersion system refines the spherulites to 5.2μm, thereby improving the uniformity of stress transfer. In addition, the ionic liquid forms a solvation layer in the polyol phase, which significantly reduces the shear viscosity of the prepolymer by reducing the melt viscosity and interfacial energy, ensuring the continuity and interfacial compatibility of the TPU network in the subsequent blending process, and suppressing the stress concentration crack source caused by local phase separation.

[0104] The epoxy compound 1,2-epoxyhexadecane was activated by ionic liquid at 60℃ and the ring was opened to form a zwitterionic structure containing hydroxyl groups ([BMIM] + -CH2-CH(OH)-OC 16 H 33 ), the newly generated hydroxyl groups directly compensate for the active sites (-NCO) of the chain extender consumed by the ionic liquid, narrowing the molecular weight distribution width of TPU and restoring the extension energy absorption capacity of the polymer chain; in addition, the C 16 Long chain alkyl (-OC 16 H 33 ) acts as a molecular bridge, with one end anchored on the montmorillonite surface and the other end embedded in the POM amorphous region, forming a physical entanglement network. This structure induces micro-area plastic deformation of the POM matrix under impact load, increasing the elongation at break from 55% to 85%, avoiding the problem of rigidity loss in traditional toughening;

[0105] Ionic liquids and epoxy compounds produce synergistic effects:

[0106] Interference source in situ functional transformation: free [BMIM] + Originally a source of interference in the chain extension reaction, it is transformed into a chain extender containing active hydroxyl groups after epoxy ring opening, simultaneously eliminating defects and regenerating functions. Through molecular reconstruction, the phase separation risk caused by traditional external chain extenders is avoided.

[0107] Multi-level reinforcement construction: a three-layer structure of clay, ionic liquid and epoxy long chain is formed on the surface of montmorillonite, wherein the bottom layer: ionic liquid electrostatically anchors the montmorillonite layer; the middle layer: imidazole ring provides epoxy ring opening active sites; the upper layer: C 16 The alkyl chains penetrate the amorphous region of POM to form an entangled network. This structure can maintain the stability of the interlayer spacing, significantly improve the interfacial bonding energy, and achieve efficient stress transfer between the nano-reinforcement and the matrix.

[0108] Energy dissipation dual-path synergy: TPU network absorbs energy through molecular chain slippage. In addition, C 16The alkyl chain induces shear yield in the amorphous region of POM and induces silver streak expansion; the dual-path synergy changes the impact energy from a single mechanism to a dual-mechanism coupling, and the notch impact strength is increased by 46%.

[0109] The synergistic effect of ionic liquids and epoxy compounds:

[0110] Impact toughness: notched impact strength is significantly improved;

[0111] Ductility: The elongation at break is increased to 85%, ensuring that the liner structure does not break brittlely when impacted;

[0112] Rigidity-toughness balance: thermal deformation temperature only drops by 4%, penetration resistance>5000N;

[0113] Through the dual mechanism of electrostatic intercalation of ionic liquid combined with rheological regulation and chain extension compensation of epoxy hexadecane combined with interface entanglement, combined with the synergistic molecular reconstruction, three-layer reinforced structure and dual-path energy dissipation effect, the long-standing problem of rigidity-toughness balance in the field of POM toughening is solved, making the material improve the impact strength (22kJ / m 2 ) and ductility (85%) indicators, while meeting the EN 1078 helmet safety standard, and is suitable for areas requiring dynamic mechanical protection, such as sports protective gear.

[0114] Example 2: The above-mentioned Example 1 achieves toughening modification of the gasket material by introducing ionic liquids and epoxy compounds. The ionic liquid solves the problem of nucleating agent agglomeration causing the POM spherulites to be too large, thereby reducing the melt viscosity; the epoxy compound compensates for the active sites of the chain extender to form a physical entanglement network; the two work together to achieve functional transformation of the interference source, construct a multi-level reinforcement, and realize dual-path coordination of energy dissipation, thereby solving the problem of toughening and toughness balance of POM and meeting safety standards. In order to further improve its performance, further improvements are made on the basis of Example 1.

[0115] The epoxy compound further includes 9-octyl heptadecane epoxy, and the mass ratio of 9-octyl heptadecane epoxy to 1,2-epoxy hexadecane is 1:1.4;

[0116] In step S1, the following improvements are made in preparing the chin protection pad material for a sports helmet, specifically:

[0117] S12. Montmorillonite pre-intercalation treatment;

[0118] 1,2-epoxyhexadecane and 9-octylheptadecane epoxy were added simultaneously;

[0119] React at 750 rpm for 40 min at 55±1°C;

[0120] Step 3: prepolymer synthesis process;

[0121] MDI was added and reacted at 82℃ for 42 min;

[0122] S13. Preparation of the prepolymer;

[0123] The polyether polyol was mixed with the expanded montmorillonite compound;

[0124] The polyol wrapped the compound by stirring at low speed at 40℃ for 10 min (500 rpm);

[0125] MDI was added and reacted at 85℃ for 40 min under nitrogen protection to form a TPU prepolymer containing intercalated montmorillonite;

[0126] S15. In-situ blending reaction;

[0127] Temperature adjustment of the twin-screw blending:

[0128] The temperature was set to a seven-zone gradient: 185℃, 195℃, 200℃, 200℃, 190℃, 175℃, and 100℃ (the die head);

[0129] The main machine rotation speed was 215 rpm;

[0130] After pelletizing, two-stage drying was used:

[0131] Hot air drying at 75℃ for 4 hours to remove free small molecules;

[0132] Vacuum drying at 60℃ for 2 hours to eliminate branched end hydroxyl groups.

[0133] The technical scheme of the embodiment was tested based on the experimental group 2 of example 1, as experimental group 4, which was prepared by the technical scheme of the embodiment. The difference between experimental group 4 and experimental group 2 was that the epoxy compound further included 9-octyl heptadecane epoxy, and the mass ratio of 9-octyl heptadecane epoxy to 1,2-epoxyhexadecane was 1:1.4. The detection results are described in Table 4 as follows:

[0134] Table 4

[0135]

[0136] The technical scheme of the embodiment has at least the following technical effects or advantages:

[0137] By introducing the epoxy compound 9-octyl heptadecane epoxy (C 18 with an octyl branched chain) with a specific branched structure, and the original 1,2-epoxyhexadecane (linear C 16 ) and ionic liquid to form a synergistic effect, based on the triple effects of topological anchoring enhancement, free volume regulation, and ion and branched chain synergistic barrier, this scheme solves the problems of low-temperature impact failure and hygrothermal aging performance degradation of the material, and improves the fatigue resistance.

[0138] In the molecular structure of 9-octyl heptadecanede epoxy, the octyl side chain (C8H 17 ) is located at the 9th carbon atom of the main chain, forming a tree-root-like three-dimensional topological configuration. The branched chain can be embedded in the interlayer defect site of montmorillonite (interlayer K + Vacancies, etc.), through the synergistic effect of van der Waals forces and hydrogen bonds, a hook-shaped physical lock is generated, which increases the binding energy. Compared with the linear interpenetration of straight-chain alkyl groups, this structure reduces the interlayer thermal shrinkage rate from 2.0% to 0.5%, inhibiting the slippage of layers in hot and humid environments and causing performance degradation. In addition, the stereo configuration of the octyl side chains can increase the free volume fraction of the amorphous region of POM, reducing the glass transition temperature (Tg) from -60°C to -73°C, and endowing the material with low-temperature plastic deformation ability.

[0139] Synergistic effect with linear epoxy: functional complementarity, among which linear C 16 By providing active hydroxyl groups through rapid ring opening, the consumption of chain extension reaction is compensated to ensure the recovery of TPU molecular weight; branched C 18 The octyl side chains physically anchor the interlayer structure to prevent thermal migration of spacers. The two achieve a dynamic balance through a mass ratio of 1:1.4, of which the straight chain accounts for about 60%, ensuring basic chain extension efficiency, and the side chain accounts for about 40%, enhancing stability in extreme environments.

[0140] Crack propagation optimization: When the silver cracks induced by the linear alkyl group extend to the branched region, the octyl branch changes the stress field distribution through the crack tip bifurcation effect, increasing the energy dissipation rate by 40% compared with the single material, extending the impact crack propagation path, and improving the notched impact strength;

[0141] Synergistic enhancement with ionic liquids: ionic liquids ([BMIM] + ) provides anchor points for the side chains, forming a complex of ion bridging and side chain locking, thereby forming a thermally stabilized interlayer structure. The side chain insertion depth and stability are improved. The hexafluorophosphate anion forms a hydrophobic barrier, which together with the octyl side chain blocks the penetration of water molecules and prevents hydrolysis.

[0142] The effects produced by introducing the epoxy compound 9-octyl heptadecanede epoxy having a specific branched structure are:

[0143] The side chains lower the glass transition temperature and ensure low-temperature plasticity, improving toughness at low temperatures; the performance retention rate after aging at 85℃ / 95%RH is increased to 93%, and the topological lock structure inhibits interlayer hydrolysis, improving moisture and heat stability: the side chains and ionic liquids synergistically passivate the surface to improve corrosion resistance; the octyl side chains convert cyclic strain energy into thermal energy through the entropy elastic energy dissipation mechanism, thereby improving fatigue life; the crack bifurcation effect extends the impact energy absorption path, increasing the penetration resistance to 4380N and enhancing safety performance.

[0144] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A chin protection pad for a sports helmet, characterized in that: The invention comprises a honeycomb structure area and a wave structure area; the liner is made of a composite material comprising polyoxymethylene, a thermoplastic polyurethane elastomer, a nucleating agent, an ionic liquid and an epoxy compound; the ionic liquid is 1-butyl-3-methylimidazole hexafluorophosphate; and the epoxy compound comprises 1,2-epoxyhexadecane and 9-octyl heptadecane epoxy.

2. The chin protection pad for a sports helmet according to claim 1, wherein: The added amount of the ionic liquid is 0.3-0.8 parts by weight, and the added amount of 1,2-epoxyhexadecane is 0.8-1.8 parts by weight.

3. The chin protection pad for a sports helmet according to claim 1, wherein: The mass ratio of the 1,2-epoxyhexadecane to the 9-octylheptadecane epoxy is 1:1.

4.

4. The chin protection pad for a sports helmet according to claim 1, wherein: The nucleating agent is montmorillonite, and the addition amount is 0.8-1.5 parts by weight; the montmorillonite is pre-treated by intercalation of ionic liquid and epoxy compound.

5. The chin protection pad for a sports helmet according to claim 1, wherein: The honeycomb structure area is printed using a hexagonal spiral filling algorithm, and the wave structure area is printed using a concentric circle topology scanning path.

6. A method for preparing a chin protection pad for a sports helmet, characterized in that: The following steps are involved: Step 1: Mix montmorillonite, 1-butyl-3-methylimidazolium hexafluorophosphate, 1,2-epoxyhexadecane and 9-octylheptadecane epoxy at 55-60° C. for 40 minutes to form a pre-intercalation composite; Step 2: Mix the pre-intercalation composite with polyether polyol, add diphenylmethane diisocyanate, and react at 80-85° C. to obtain a prepolymer; Step 3: Blend the prepolymer with a polyoxymethylene melt in a twin-screw extruder, and obtain composite material particles by granulation and drying.

7. The method for preparing a chin protection pad for a sports helmet according to claim 6, wherein: The following steps are also included: The composite material particles were 3D printed; the printing parameters included: nozzle temperature 200-205°C, hot bed temperature 100-105°C, honeycomb layer thickness 0.15mm, and wave layer thickness 0.20mm; After printing, the temperature was gradually reduced in sequence: 120°C for 30 min, 100°C for 60 min, and 80°C for 30 min.

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