Aqueous impact-protecting helmet coating

Abstract

The present application relates to the technical field of water-based paint, in particular to a helmet impact protection water-based paint, which solves the shortcomings in the prior art and comprises the following components: epoxy resin, water-based polyurethane, chitosan, polystyrene microspheres, nano-clay, acrylic resin, silicon dioxide, titanium dioxide, defoaming agent and foam inhibitor.In the present application, the epoxy resin provides the basic structure and hardness of the paint; the water-based polyurethane enhances the flexibility and wear resistance of the paint; the chitosan contributes to the biocompatibility and antibacterial function; the polystyrene microspheres, as elastomers, can absorb and disperse impact force; the nano-clay and acrylic resin further enhance the hardness and impact resistance of the paint; the addition of silicon dioxide and titanium dioxide not only improves the hardness of the paint, but also endows it with self-cleaning ability, forming a stable and excellent performance paint system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water-based coatings, in particular to a helmet impact protection water-based coating. BACKGROUND

[0002] With the improvement of modern safety awareness, helmets as important equipment to protect the head from impact injury have been widely used in military, industry, sports and other fields. The protective performance of the helmet is largely dependent on the properties of its surface coating. Traditional helmet coatings often focus on the improvement of a single function, such as hardness, wear resistance or corrosion resistance, while ignoring the comprehensive performance of the coating in complex and variable environments. Especially when subjected to high-speed impact, traditional coatings may crack or peel due to lack of sufficient toughness and energy absorption capacity, thus failing to provide effective protection for the wearer.

[0003] In recent years, water-based coatings have gradually become a research hotspot in the coatings industry due to their environmental protection, low toxicity, easy construction and other advantages. However, existing water-based coatings still have many shortcomings when applied to helmet impact protection. For example, some water-based coatings have high hardness and wear resistance, but they are difficult to effectively absorb and disperse energy when impacted, resulting in a significant reduction in the protective effect of the coating. In addition, the durability of some water-based coatings in complex environments is poor, and they may easily age, fade or degrade in performance after long-term use.

[0004] Therefore, we propose a helmet impact protection water-based coating to solve the above problems. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the prior art and propose a helmet impact protection water-based coating.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A helmet impact protection water-based coating, comprising the following components by weight: epoxy resin 20-30 parts, water-based polyurethane 20-30 parts, chitosan 5-10 parts, polystyrene microspheres 5-10 parts, nano-clay 3-5 parts, acrylic resin 10-15 parts, silica 3-5 parts, titanium dioxide 2-3 parts, defoaming agent 0.5-1 part, and foam inhibitor 0.5-1 part.

[0008] As a preferred technical solution:

[0009] A helmet impact protection water-based paint as described above, comprising the following components by weight: epoxy resin 23 parts, water-based polyurethane 26 parts, chitosan 7 parts, polystyrene microspheres 8 parts, nano-clay 4 parts, acrylic resin 12 parts, silicon dioxide 4 parts, titanium dioxide 2 parts, defoamer 0.8 parts, antifoam 0.7 parts.

[0010] A helmet impact protection water-based paint as described above, wherein the epoxy resin is one of epoxy resin e-44 or epoxy resin e-51, and the viscosity of the epoxy resin is 1000-1500 mPa·s; the water-based polyurethane is an anionic water-based polyurethane, and the average particle size is 50-100 nm; the chitosan has a molecular weight of 100-300 thousand; the polystyrene microspheres have an average particle size of 1-5 microns; the acrylic resin has a glass transition temperature of 30-50℃, and a weight average molecular weight of 50-100 thousand; the titanium dioxide has a crystal form of one of rutile or anatase, and an average particle size of 0.2-0.4 microns; the defoamer is one of dimethyl silicone oil and polyether; and the antifoam is one of hydrophobic silicon dioxide and fatty alcohol.

[0011] A helmet impact protection water-based paint as described above, wherein the chitosan and the water-based polyurethane form an interpenetrating polymer network, wherein the chitosan network provides biocompatibility and antibacterial function, and the water-based polyurethane network contributes flexibility and wear resistance; the polystyrene microspheres are elastomers with deformable cores, which are composed of cross-linked polymer networks and can change shape and absorb energy under external force, and the surface of the polystyrene microspheres is covered with a nanoscale self-healing layer, which can quickly self-repair when the microspheres are broken, maintaining the integrity of the paint.

[0012] A helmet impact protection water-based paint as described above, wherein the chitosan is modified to introduce functional groups with the ability to chelate calcium ions on the molecular chain; the acrylic resin is a copolymer with a core-shell structure, the core layer is a hard segment that provides the paint with hardness and wear resistance, and the shell layer is a soft segment that gives the paint flexibility and impact resistance; the water-based polyurethane has a star structure, the central core is a rigid aromatic structure that provides high strength and wear resistance, and the periphery is a flexible aliphatic segment that gives the paint excellent elasticity and cold resistance; the titanium dioxide nanoparticles have a thin film of metal oxide with photocatalytic activity on the surface, and are designed into nano-shaped structures, including nanoflowers, nanotrees or nanostars; and the polystyrene microspheres have a core-shell structure with gradient density distribution inside, and / or are modified with nanoscale silica particles on the surface.

[0013] A helmet impact protection water-based paint, according to the above, the core-shell structure nanoparticles are constructed according to the silica as the core and the titanium dioxide as the shell, the structure can combine the hardness of the silica and the photocatalytic performance of the titanium dioxide, enhance the self-cleaning ability of the paint, set the self-cleaning ability index as SCI, and:

[0014] SCI = \frac{k \times A surface}{M particle}

[0015] Wherein: k is the photocatalytic degradation rate constant; A surface is the surface area of the nanoparticles in unit mass of the paint, which is obtained by BET specific surface area test; M particle is the mass of the nanoparticles;

[0016] k = -\frac{\l n(C / C_0)}{t}

[0017] Wherein: C is the concentration of the target pollutant after the reaction; C_0 is the initial concentration of the target pollutant before the reaction; t is the photocatalytic reaction time.

[0018] The second aspect of the present application provides a preparation method of a helmet impact protection water-based paint, comprising the following steps:

[0019] S1: using the ultrasonic-assisted high-speed stirring technology, mixing the water-based polyurethane and the chitosan solution to form a composite emulsion;

[0020] S2: dispersing the nanoclay in deionized water to form a stable suspension, slowly adding the acrylic resin under stirring conditions to form a dense pre-coating emulsion;

[0021] S3: mixing the preheated epoxy resin with the diluent to reduce the viscosity, gradually adding the silica and the titanium dioxide to ensure uniform dispersion of each component, and obtaining an epoxy resin base system;

[0022] S4: mixing the composite emulsion and the pre-coating emulsion under controlled stirring speed to avoid damaging the stability of the emulsion, slowly adding the epoxy resin base system into the above mixed emulsion, simultaneously adding the defoaming agent and the foam inhibitor, and continuously stirring until each component is completely fused to form a uniform and stable paint system;

[0023] S5: dispersing the polystyrene microspheres, then slowly adding the dispersed polystyrene microspheres into the paint system in S4 under continuous stirring, continuing to stir for a period of time to ensure uniform distribution of the polystyrene microspheres in the paint, and obtaining the helmet impact protection water-based paint.

[0024] As a preferred technical solution:

[0025] The preparation method of the helmet impact protection water-based paint as described above, in S2, the acrylic resin molecules are adsorbed on the surface of the nanoclay layer by layer by using the layer-by-layer assembly technology, and a pre-coating emulsion with a multi-layer structure is constructed.

[0026] The preparation method of the helmet impact protection water-based paint as described above, S4 specifically comprises the following steps:

[0027] S41: Under the control of the stirring speed, the composite emulsion is first pre-mixed with the pre-coating emulsion, and the variable speed stirring technology is used, the initial stirring speed is set to 400 rpm, and the stirring speed is gradually increased to 900 rpm;

[0028] S42: While pre-mixing, a dynamic mixer is prepared, which is provided with rotating elements inside and can generate strong shear force and impact force while controlling the stirring speed, and the dynamic mixer is preheated to reduce the influence of temperature difference on the mixing process;

[0029] S43: The preheated epoxy resin base system is slowly added to the dynamic mixer, and at the same time, the rotating elements of the dynamic mixer generate strong shear force and impact force;

[0030] S44: During the mixing process, when the amount of the epoxy resin base system added reaches 50% of the total amount, the defoaming agent and the foam inhibitor are slowly added;

[0031] S45: During the whole mixing process, the viscosity, temperature and bubble situation of the mixing system are continuously monitored, and the continuous stirring time is adjusted according to the monitoring results;

[0032] S46: When all components are completely fused, the stirring is stopped, and the finished paint system is post-treated to ensure the purity and coating effect of the paint.

[0033] The preparation method of the helmet impact protection water-based paint as described above, S5 specifically comprises the following steps:

[0034] S51: The polystyrene microspheres are placed in a solvent containing a dispersant, and a high-speed dispersing machine is used for preliminary dispersion, the polystyrene microsphere suspension after preliminary dispersion is placed in an ultrasonic processor, and an optical microscope is used to evaluate the particle size distribution and dispersion state of the dispersed polystyrene microspheres, to ensure that the microspheres achieve the required uniform dispersion effect;

[0035] S52: Before adding the polystyrene microspheres, the paint system obtained in S4 is pre-stirred, and under the condition of continuous stirring, the dispersed polystyrene microsphere suspension is gradually added to the paint system by slow pumping;

[0036] S53: After all the polystyrene microspheres are added, gradually increase the stirring speed, and evaluate the stability of the stirred coating system, including observing whether stratification, precipitation or phase separation occurs, and measuring the rheological properties of the coating by a rheometer. If the coating system has good stability, proceed with post-processing, and then seal and package to obtain the final helmet impact protection water-based coating product.

[0037] Compared with the prior art, the beneficial effects of the present application are:

[0038] Chitosan and waterborne polyurethane form an interpenetrating polymer network, combining the biocompatibility and antibacterial properties of chitosan, and the flexibility of waterborne polyurethane, thereby maintaining the flexibility of the coating while imparting antibacterial functionality. The formation of this network structure greatly enhances the overall performance of the coating, making it more suitable for applications such as helmets that require both protection and hygiene;

[0039] Polystyrene microspheres have a deformable core that can change shape and absorb energy under external force, effectively dispersing impact stress and improving the impact resistance of the coating. Epoxy resin and waterborne polyurethane as the main resins of the coating, together provide high strength and toughness, further enhancing the impact resistance of the coating. The addition of nano-clay effectively prevents crack propagation through its lamellar structure, improving the crack resistance of the coating;

[0040] Modified chitosan can chelate calcium ions, and according to the concentration change of calcium ions in the environment, it can shrink or elongate, imparting self-adaptability and intelligent responsiveness to the coating, allowing it to automatically adjust its performance according to different use conditions. The waterborne polyurethane network contributes flexibility and wear resistance, combined with the rigid structure of the epoxy resin, forming a coating system with both rigidity and flexibility. The core-shell structure of the acrylic resin provides hardness in the core layer and flexibility and impact resistance in the shell layer, further enhancing the overall performance of the coating;

[0041] Titanium dioxide nanoparticles are surface-modified with a photocatalytically active metal oxide film and designed into a nano-shaped structure, enhancing the photocatalytic performance of the particles, giving the coating excellent light scattering, light absorption and light conversion properties. By constructing silica-titania core-shell structure nanoparticles, the hardness of silica and the photocatalytic properties of titanium dioxide are combined, significantly enhancing the self-cleaning ability of the coating;

[0042] The high specific surface area and thickening effect of nano-clay are combined with the film-forming property and water resistance of acrylic resin to form a dense waterproof coating that effectively resists the penetration of water and moisture. This improvement in waterproof performance complements the impact resistance of the polystyrene microspheres, together enhancing the stability and durability of the coating in various environments.

[0043] In summary, by adding polystyrene microspheres and nanoclay and other components, the coating can absorb and disperse external impact force, effectively protecting the internal structure of the helmet from damage; the synergistic effect of water-based polyurethane and acrylic resin makes the coating not only have excellent wear resistance, but also maintain good flexibility, thereby prolonging the service life of the helmet; the modified chitosan can give the coating self-adaptive and intelligent responsiveness, so that it can maintain good performance in different environments; by constructing titanium dioxide nanoparticles with photocatalytic activity, the coating has self-cleaning ability and can effectively degrade organic pollutants attached to the surface; using a water-based system, compared with traditional oily coatings, it is more environmentally friendly and harmless to human health. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a transmission electron micrograph of the microspheres in Example Four of the present application;

[0045] Figure 2 is a data fold line of the examples, control examples, and comparative examples of the present application Figure One ;

[0046] Figure 3 is a data fold line of the examples, control examples, and comparative examples of the present application Figure Two ;

[0047] Figure 4 is a data fold line of the examples, control examples, and comparative examples of the present application Figure Three ;

[0048] Figure 5 is a data fold line of the examples, control examples, and comparative examples of the present application Figure Four . DETAILED DESCRIPTION

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. If there is a conflict between usages of terms among documents For example, a range of 1-50 should be understood as including any number, combination of numbers, or sub-range selected from the integers between 1 and 50, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values between the integers, e.g., 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to sub-ranges, "nested sub-ranges" extending from either end of the range are specifically contemplated. For example, exemplary nested sub-ranges of the range 1-50 can include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in the other direction.

[0050] The application is further explained with reference to the specific examples below, in which the experimental methods described below are routine methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified.

[0051] The headgear impact protection water-based paint comprises the following components in parts by weight: epoxy resin 20-30 parts, water-based polyurethane 20-30 parts, chitosan 5-10 parts, polystyrene microspheres 5-10 parts, nano-clay 3-5 parts, acrylic resin 10-15 parts, silicon dioxide 3-5 parts, titanium dioxide 2-3 parts, defoaming agent 0.5-1 part, and foam inhibitor 0.5-1 part.

[0052] The epoxy resin is one of epoxy resin e-44 or epoxy resin e-51, the viscosity of the epoxy resin is 1000-1500 mPa·s; the water-based polyurethane is an anionic water-based polyurethane, the average particle size is 50-100 nanometers; the molecular weight of chitosan is 100-300 thousand; the average particle size of polystyrene microspheres is 1-5 microns; the glass transition temperature of the acrylic resin is 30-50 DEG C, and the weight average molecular weight is 50-100 thousand; the crystal form of titanium dioxide is one of rutile or anatase, the average particle size is 0.2-0.4 microns; the defoaming agent is one of dimethyl silicone oil and polyether; the antifoaming agent is one of hydrophobic silicon dioxide and fatty alcohol.

[0053] The anionic water-based polyurethane and chitosan form an interpenetrating structure in the helmet impact protection water-based paint. Chitosan, as a natural high molecular compound, has good biocompatibility and no toxic effect on human tissues, organs and cells. The combination of chitosan and anionic water-based polyurethane to form an interpenetrating structure can significantly improve the biological safety of the paint and reduce the risk of allergic reactions or toxicity during use.

[0054] Chitosan has the special function of antibacterial and anti-inflammatory, which is effectively preserved in the paint. Through the interpenetrating structure with water-based polyurethane, the paint not only has flexibility, but also integrates the antibacterial performance of chitosan, so as to provide an additional layer of health protection in the helmet application and reduce the possibility of bacterial growth and spread.

[0055] Anionic water-based polyurethane is known for its excellent flexibility and wear resistance. Through the interpenetrating structure with chitosan, the flexibility and wear resistance are further enhanced. The paint can effectively absorb and disperse energy when impacted, reducing direct damage to the head, while maintaining the integrity and protective performance of the coating.

[0056] The formation of interpenetrating polymer network structure makes chitosan and water-based polyurethane form a close combination. This network structure not only enhances the stability inside the paint, but also improves the adhesion between the paint and the helmet substrate. During long-term use, the paint can maintain stable performance and is not prone to peeling, cracking or performance degradation.

[0057] It should be noted that chitosan and water-based polyurethane construct an interpenetrating polymer network, in which the chitosan network provides biocompatibility and antibacterial function, while the water-based polyurethane network contributes flexibility and wear resistance; polystyrene microspheres are elastomers with deformable core, the core is composed of cross-linked polymer network, which can change shape and absorb energy under external force, the surface of polystyrene microspheres is covered with a nano self-healing layer, which can quickly repair itself when the microspheres are broken, maintaining the integrity of the paint.

[0058] To achieve the specific implementation in the helmet impact protection water-based paint, chitosan and water-based polyurethane to build interpenetrating polymer network, and the introduction of polystyrene microspheres with specific structure to enhance the impact resistance, the following examples are given:

[0059] I. Construction of interpenetrating polymer network

[0060] Raw material selection and ratio:

[0061] Water-based polyurethane: select water-based polyurethane dispersion with excellent flexibility and wear resistance, such as water-based polyurethane synthesized based on polyether glycol and toluene diisocyanate (TD I), with solid content of 30%. Chitosan: select chitosan powder with deacetylation degree higher than 90%, with good biocompatibility and antibacterial performance. The mass ratio of chitosan to water-based polyurethane is 1:3 to ensure that the two can form a good interpenetrating polymer network.

[0062] Preparation of interpenetrating polymer network: dissolve chitosan powder in acetic acid solution to obtain chitosan acetic acid solution. Mix water-based polyurethane dispersion and chitosan acetic acid solution according to the above ratio, and add appropriate amount of crosslinking agent (such as diisocyanate) and catalyst. Under stirring condition, heat the mixture to appropriate temperature (such as 60-80℃), react for several hours, until the stable interpenetrating polymer network structure is formed.

[0063] Performance characterization: the structure of interpenetrating polymer network is characterized by infrared spectroscopy (I R) and scanning electron microscopy (SEM) and other means. Test the biocompatibility and antibacterial performance of the coating to ensure the effective function of chitosan network. Test the flexibility and wear resistance of the coating to verify the contribution of water-based polyurethane network.

[0064] II. Preparation and properties of polystyrene microspheres

[0065] Raw material selection and ratio: crosslinking agent: such as divinylbenzene (DVB), used to build the deformable core of polystyrene microspheres. Styrene monomer: as the main component of polystyrene microspheres. Initiator: such as azobisisobutyronitrile (AI BN), used to initiate polymerization reaction.

[0066] Preparation of polystyrene microspheres: mix styrene monomer, crosslinking agent and initiator according to certain ratio, and add appropriate amount of dispersant (such as polyvinylpyrrolidone, PVP) to maintain the stability of microspheres. Under stirring condition, heat the mixture to appropriate temperature (such as 70-80℃), react for several hours, until the stable polystyrene microsphere emulsion is formed. Through centrifugation, washing and drying steps, polystyrene microspheres with deformable core are obtained.

[0067] Coating of self-healing layer: polystyrene microspheres are dispersed in a solution containing nanoscale self-healing material (such as a mixed solution containing nanosilica and self-healing polymer). Through physical or chemical methods (such as electrostatic adsorption, chemical bonding, etc.), the self-healing layer is uniformly coated on the surface of the polystyrene microspheres.

[0068] Performance characterization: the morphology of the polystyrene microspheres and the coverage of the self-healing layer are observed by SEM and TEM, etc. The deformability and energy absorption capacity of the microspheres under external force are verified by compression test and impact test, etc. The effect and repair speed of the self-healing layer are observed and recorded by simulating the rupture of the microspheres.

[0069] Specific data example: the solid content of the waterborne polyurethane is 30%. The mass ratio of chitosan to waterborne polyurethane is 1:3. The amount of crosslinking agent divinylbenzene is 5% of the mass of styrene monomer. The amount of initiator azobisisobutyronitrile is 0.5% of the mass of styrene monomer. The average diameter of the polystyrene microspheres is 5 microns. The thickness of the self-healing layer is nanoscale, and the specific value can be determined by TEM measurement.

[0070] It should be noted that the chitosan is modified and has functional groups with the ability to chelate calcium ions on the molecular chain. In a solution containing calcium ions, the chitosan molecules can "absorb calcium ions" and shrink, while in a solution with the ability to chelate calcium ions, they "lose calcium ions" and elongate, giving the coating self-adaptability and intelligent responsiveness; the acrylic resin is a copolymer with core-shell structure, the core layer is a hard segment, providing the coating with hardness and wear resistance; the shell layer is a soft segment, giving the coating flexibility and impact resistance; the waterborne polyurethane is a star-shaped structure, with a rigid aromatic structure at the center, providing high strength and wear resistance; while the periphery is a flexible aliphatic segment, giving the coating excellent elasticity and cold resistance; the titanium dioxide nanoparticles are modified with a thin film of metal oxide with photocatalytic activity on the surface by atomic layer deposition technology, and designed into nano-shaped structures, including nanoflowers, nanotrees or nanostars; these structures not only enhance the photocatalytic performance of the particles, but also give the coating excellent light scattering, light absorption and light conversion performance; the polystyrene microspheres have a core-shell structure with gradient density distribution inside, with high density and hardness in the core part to improve the impact resistance of the coating; while the shell part has low density and good elasticity to improve the touch and wear resistance of the coating; and / or the surface of the polystyrene microspheres is modified with nanoscale silica particles, further enhancing the hardness and scratch resistance of the coating.

[0071] In the helmet impact protection waterborne coating, to achieve the modification of chitosan, the core-shell structure design of acrylic resin, the star-shaped structure of waterborne polyurethane, the surface modification of titanium dioxide nanoparticles, and the gradient density core-shell structure and surface modification of polystyrene microspheres, the following examples are given:

[0072] I. Modification of chitosan

[0073] Raw material selection and ratio: Chitosan: Chitosan powder with deacetylation degree above 90% is selected. Modifier: Functional groups with calcium ion chelating ability (such as ethylenediaminetetraacetic acid, EDTA) or its derivatives. The mass ratio of chitosan to modifier is 10:1.

[0074] Modification steps: Dissolve chitosan powder in 1% acetic acid solution to prepare chitosan solution. Dissolve the modifier in an appropriate amount of solvent, then slowly add it to the chitosan solution while stirring. React at room temperature for 24 hours to allow the modifier to fully graft onto the molecular chain of chitosan. After the reaction is complete, precipitate the modified chitosan with ethanol and wash it several times with deionized water to remove unreacted modifier and impurities. Finally, dry the modified chitosan to constant weight to obtain chitosan with calcium ion chelating ability.

[0075] Performance verification: Characterize the structure of modified chitosan by infrared spectroscopy (IR) and nuclear magnetic resonance hydrogen spectrum (^1H-NMR) to confirm the successful grafting of functional groups. Disperse the modified chitosan in a solution containing calcium ions and observe the shrinkage phenomenon after absorbing calcium ions. Disperse the shrunk chitosan in a solution with calcium ion chelating ability and observe the elongation phenomenon after losing calcium ions.

[0076] II. Design of core-shell structure of acrylic resin

[0077] Raw material selection and ratio: Hard segment monomer: Methyl methacrylate (MMA) provides hardness and wear resistance. Soft segment monomer: Butyl acrylate (BA) imparts flexibility and impact resistance. Initiator: Azobis isobutyronitrile (AIBN). The mass ratio of hard segment to soft segment monomers is 7:3.

[0078] Core-shell structure preparation steps:

[0079] In a three-necked flask equipped with a stirrer, thermometer, and reflux condenser, add an appropriate amount of solvent and hard segment monomer MMA, as well as initiator AIBN. Heat to 75°C to start the polymerization reaction and form a hard segment core. When the hard segment core reaches a certain size, start adding the soft segment monomer BA, and continue the reaction at the same temperature to form a shell layer of soft segments on the surface of the hard segment core. After the reaction is complete, precipitate the core-shell structured acrylic resin with ethanol and wash it several times with deionized water to remove unreacted monomers and impurities. Finally, dry the acrylic resin to constant weight.

[0080] Performance verification: The core-shell structure of the acrylic resin was observed by transmission electron microscopy (TEM). The hardness and abrasion resistance of the coating were tested to verify the contribution of the hard segment core. The flexibility and impact resistance of the coating were tested to verify the contribution of the soft segment shell.

[0081] III. Star-shaped structure design of waterborne polyurethane

[0082] Raw material selection and ratio: Rigid aromatic diisocyanate: such as toluene diisocyanate (TDI), providing high strength and abrasion resistance. Flexible aliphatic diol: such as polyethylene glycol (PEG), imparting excellent elasticity and cold resistance. Trifunctional alcohol: as the central core of the star-shaped structure, such as glycerol or pentaerythritol.

[0083] Star-shaped structure preparation steps: Add the trifunctional alcohol and an appropriate amount of solvent to a three-necked flask and heat to an appropriate temperature. Slowly add the rigid aromatic diisocyanate while stirring, allowing the trifunctional alcohol to react with the diisocyanate to form the central core of the star-shaped structure. Subsequently, add the flexible aliphatic diol and continue the reaction, allowing the flexible segments to attach to the central core to form the star-shaped structure of the waterborne polyurethane. After the reaction is complete, wash with deionized water several times to remove unreacted raw materials and impurities. Finally, dry the waterborne polyurethane to a constant weight and disperse it in water to form an aqueous dispersion.

[0084] Performance verification: The star-shaped structure of the waterborne polyurethane was characterized by gel permeation chromatography (GPC) and nuclear magnetic resonance hydrogen spectrum (^1H-NMR), etc. The tensile strength and abrasion resistance of the coating were tested to verify the contribution of the rigid aromatic structure. The elasticity and cold resistance of the coating were tested to verify the contribution of the flexible aliphatic segment.

[0085] IV. Surface modification of titanium dioxide nanoparticles

[0086] Raw material selection and ratio: Titanium dioxide nanoparticles: anatase titanium dioxide with a particle size of 20 nanometers was selected. Metal oxide precursor: such as tetrabutyl titanate, used to deposit a thin film of metal oxide with photocatalytic activity. Solvent: ethanol or isopropyl alcohol.

[0087] Surface modification steps: Disperse the titanium dioxide nanoparticles in a solvent to form a stable suspension. Dissolve the metal oxide precursor in another portion of the solvent and then slowly add it to the titanium dioxide suspension while stirring. React at room temperature for 24 hours to allow the metal oxide precursor to hydrolyze and condense into a film on the surface of the titanium dioxide nanoparticles. Obtain the titanium dioxide nanoparticles with a thin film of metal oxide on the surface by steps such as centrifugation, washing, and drying.

[0088] Nano-shape structure design: using hydrothermal or solvothermal method, the surface modified titanium dioxide nanoparticles are synthesized under high temperature and high pressure conditions to form nano-flower, nano-tree or nano-star shape structure.

[0089] Performance verification: the shape and surface modification of titanium dioxide nanoparticles are observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The photocatalytic performance, light scattering performance, light absorption performance and light conversion performance of the coating are tested.

[0090] Five, gradient density core-shell structure and surface modification of polystyrene microspheres

[0091] Raw material selection and ratio: polystyrene monomer: styrene (St). Initiator: azobisisobutyronitrile (AIBN). Density regulator: such as high-density inorganic nanoparticles (such as silicon dioxide) and low-density organic matter (such as polyethylene glycol). Surface modifier: nanoscale silica particles.

[0092] Preparation steps of gradient density core-shell structure: in a three-necked flask equipped with a stirrer, a thermometer and a reflux condenser, add appropriate amount of solvent and polystyrene monomer, and initiator AIBN. Heat to 70℃, start the polymerization reaction. In the early stage of the reaction, add high-density inorganic nanoparticles as the core part, so that the core part has high density and high hardness. With the progress of the reaction, gradually add low-density organic matter as the shell part, so that the shell part has low density and good elasticity. After the reaction is completed, the polystyrene microspheres with gradient density core-shell structure are precipitated with ethanol, and washed with deionized water for several times.

[0093] Surface modification steps: disperse the precipitated polystyrene microspheres in an appropriate amount of solvent to form a stable suspension. Disperse nanoscale silica particles in another portion of solvent, then slowly add to the polystyrene microsphere suspension while stirring. React at room temperature for a period of time to allow the silica particles to uniformly adsorb on the surface of the polystyrene microspheres. Through the steps of centrifugation, washing and drying, obtain the polystyrene microspheres with nanoscale silica particles on the surface.

[0094] Performance verification: the gradient density core-shell structure and surface modification of polystyrene microspheres are observed by scanning electron microscope (SEM). The impact resistance, touch and wear resistance of the coating are tested. The hardness and scratch resistance of the coating are tested.

[0095] Specific data examples: the mass ratio of chitosan to modifier is 10:1. The mass ratio of hard segment to soft segment monomer in acrylic resin is 7:3. The molar ratio of rigid aromatic diisocyanate to flexible aliphatic diol in waterborne polyurethane is 1:3. The particle size of titanium dioxide nanoparticles is 20 nanometers. The average diameter of polystyrene microspheres is 5 microns. The particle size of surface-modified nanoscale silica particles is 10 nanometers.

[0096] It should be noted that the core-shell structure nanoparticles are constructed according to the structure of silica as the core and titanium dioxide as the shell. This structure can combine the hardness of silica and the photocatalytic performance of titanium dioxide, enhance the self-cleaning ability and durability of the coating, and set the self-cleaning ability index as SCI, then: SCI = \frac{k \times A surface}{M particle};

[0097] Where: k is the photocatalytic degradation rate constant; A surface is the surface area of the nanoparticles per unit mass of coating, obtained by BET specific surface area test; M particle is the mass of the nanoparticles;

[0098] k = -\frac{\l n(C / C_0)}{t};

[0099] Where: C is the concentration of the target pollutant after the reaction; C_0 is the initial concentration of the target pollutant before the reaction; t is the photocatalytic reaction time.

[0100] In order to specifically realize the helmet impact protection water-based paint, according to the structure of silica as the core and titanium dioxide as the shell, and combining the characteristics of this structure to enhance the self-cleaning ability and durability of the coating, a detailed example is given as follows:

[0101] I. Material preparation

[0102] Silica core: select silica particles with an average particle size of 50 nanometers as the core. Titanium dioxide shell: select rutile titanium dioxide as the shell material; other auxiliary materials.

[0103] II. Preparation of core-shell structure nanoparticles

[0104] Disperse the silica particles in a suitable solvent to form a stable suspension.

[0105] Add titanium dioxide precursor to the suspension, and control the reaction conditions (such as temperature, pH value, reaction time, etc.) to make titanium dioxide uniformly deposit on the surface of silica particles to form a core-shell structure.

[0106] The formed core-shell structure nanoparticles are washed, dried and calcined to obtain stable nanoparticles.

[0107] III. Preparation of the coating and performance testing

[0108] The prepared core-shell structure nanoparticles are mixed with other coating ingredients and stirred uniformly to obtain a helmet impact protection water-based coating. The coating is applied to the helmet shell and necessary drying and curing processes are performed.

[0109] Self-cleaning ability test: A typical organic pollutant (such as oil or dirt) is selected as the target pollutant. A certain amount of target pollutant is dropped on the helmet shell coated with the coating, and the initial concentration C_0 is recorded. The helmet is placed under simulated sunlight irradiation and undergoes photocatalytic reaction for a certain time. After the reaction, the concentration C of the target pollutant after the reaction is measured, and the photocatalytic reaction time t is recorded.

[0110] According to the above formula, the photocatalytic degradation rate constant k and the self-cleaning ability index SCI are calculated.

[0111] Data results: Average particle size of silica core: 50 nm; Thickness of titanium dioxide shell: 10 nm; BET specific surface area test results: Surface area of nanoparticles in unit mass of coating: 100 m / g (set value, actual value needs to be determined by experiment); Mass of nanoparticles: 0.1 g (mass of nanoparticles in the coating used for testing); Photocatalytic reaction time: 2 hours; Initial pollutant concentration C_0: 100 mg / L (set value, representing the initial concentration of oil or dirt); Pollutant concentration C after reaction: 20 mg / L (set value, representing the pollutant concentration after photocatalytic reaction); According to the above data, we can calculate:

[0112] Photocatalytic degradation rate constant k = -\frac{\l n(20 / 100)}{2} = 0.693 / hour (set to 2 hours, the pollutant concentration decreases from 100 mg / L to 20 mg / L)

[0113] Self-cleaning ability index SCI = \frac{0.693\t imes 100}{0.1} = 693 (the larger the value, the stronger the self-cleaning ability of the coating)

[0114] Through the above example, we show how to specifically implement the use of core-shell structure nanoparticles with silica as the core and titanium dioxide as the shell in the helmet impact protection water-based coating to enhance the self-cleaning ability and durability of the coating. This structure combines the hardness of silica and the photocatalytic performance of titanium dioxide, providing better protection for the helmet.

[0115] Example One

[0116] A helmet impact protection water-based paint, comprising the following components by weight: epoxy resin (epoxy resin e-44, Nantong Xingchen synthetic materials) 20 parts, water-based polyurethane (anionic water-based polyurethane, Wanhua Chemical) 20 parts, chitosan (Shandong chitosan production plant) 5 parts, polystyrene microspheres (China Science and Technology Co. Optimized Nanotechnology Co., Ltd.) 5 parts, nano clay (Sigma- Aldrich) 3 parts, acrylic resin (Xiamen Aikema Chemical Co., Ltd.) 10 parts, silicon dioxide 3 parts, titanium dioxide (rutile type, Sichuan Longpan) 2 parts, defoaming agent (dimethyl silicone oil) 0.5 parts, foam inhibitor (hydrophobic silicon dioxide) 0.5 parts.

[0117] A helmet impact protection water-based paint preparation method is also given in the example, comprising the following steps:

[0118] S1: Using ultrasonic assisted high-speed stirring technology, the ultrasonic frequency is 20 kHz, the stirring speed is 1000 rpm, the mixing time is 30 minutes, the temperature is controlled at 25℃, the water-based polyurethane and chitosan solution are mixed, the biocompatibility and antibacterial property of chitosan are used, and the flexibility of water-based polyurethane is combined to form a composite emulsion;

[0119] S2: Using layer-by-layer assembly technology, the acrylic resin molecules are adsorbed on the surface of the nano clay layer by layer, and the layer-by-layer assembly is performed 3 times, the pH value is controlled at 7, and the stirring speed is 500 rpm, to construct a pre-coating emulsion with a multi-layer structure;

[0120] S3: Mix the preheated epoxy resin with the diluent, the preheating temperature is 60℃, the mixing time is 15 minutes, the viscosity is reduced, the silica and titanium dioxide are gradually added, and the components are uniformly dispersed to obtain an epoxy resin base system;

[0121] S4: Mix the composite emulsion and the pre-coating emulsion under controlled stirring speed to avoid damaging the stability of the emulsion, slowly add the epoxy resin base system to the mixed emulsion, and mix using a dynamic mixer, the stirring speed of the dynamic mixer is 2000 rpm, the mixing time is 30 minutes, and the temperature is controlled at 30℃. This device can generate strong shear force and impact force through internal rotating elements while controlling the stirring speed, so as to ensure that all components are completely fused in a short time, and defoaming agent and foam inhibitor are added at the same time to reduce the bubbles generated during the mixing process. Continue stirring until all components are completely fused to form a uniform and stable paint system;

[0122] S5: The polystyrene microspheres are dispersed for 1 hour to ensure uniform dispersion. Under continuous stirring at a speed of 800 rpm, the dispersed polystyrene microspheres are slowly added to the coating system in S4, and stirring is continued for 30 minutes to ensure uniform distribution of the polystyrene microspheres in the coating. A helmet impact protection water-based coating is obtained.

[0123] Example Two

[0124] A helmet impact protection water-based coating includes the following components by weight: epoxy resin (epoxy resin e-51) 22 parts, water-based polyurethane (anionic water-based polyurethane) 24 parts, chitosan 7 parts, polystyrene microspheres 6 parts, nano-clay 4 parts, acrylic resin 12 parts, silicon dioxide 4 parts, titanium dioxide (anatase type) 2 parts, defoamer (polyether) 0.6 parts, and foam inhibitor (fatty alcohol) 0.7 parts.

[0125] A helmet impact protection water-based coating preparation method is also provided in the example, including the following steps:

[0126] S1: Using ultrasonic-assisted high-speed stirring technology, the water-based polyurethane and chitosan solution are mixed at an ultrasonic frequency of 25 kHz and a stirring speed of 1200 rpm for 40 minutes at a temperature of 30°C. The biocompatibility and antibacterial properties of chitosan are combined with the flexibility of water-based polyurethane to form a composite emulsion;

[0127] S2: Using layer-by-layer assembly technology, the acrylic resin molecules are adsorbed on the surface of the nano-clay layer by layer, and the pre-coating emulsion with a multi-layer structure is constructed by layer-by-layer assembly for 4 times at a pH value of 8 and a stirring speed of 700 rpm;

[0128] S3: The preheated epoxy resin is mixed with the diluent at a preheating temperature of 65°C for 18 minutes to reduce the viscosity. The silica and titanium dioxide are gradually added to ensure uniform dispersion of the components, and an epoxy resin base system is obtained.

[0129] S4: The composite emulsion and the pre-coating emulsion are mixed at a controlled stirring speed to avoid damaging the stability of the emulsion. The epoxy resin base system is slowly added to the mixed emulsion, and a dynamic mixer is used for mixing at a stirring speed of 2500 rpm for 40 minutes at a temperature of 35°C. This equipment can generate strong shear force and impact force through internal rotating elements while controlling the stirring speed, ensuring complete fusion of the components in a short time. Defoamers and foam inhibitors are added at the same time to reduce the generation of bubbles during the mixing process. Continuous stirring is carried out until the components are completely fused to form a uniform and stable coating system.

[0130] S5: The polystyrene microspheres are dispersed for 1 hour to ensure uniform dispersion. Under continuous stirring at a speed of 1100 rpm, the dispersed polystyrene microspheres are slowly added to the coating system in S4, and stirring is continued for 40 minutes to ensure uniform distribution of the polystyrene microspheres in the coating. A helmet impact protection water-based coating is obtained.

[0131] Example Three

[0132] A helmet impact protection water-based coating includes the following components by weight: epoxy resin (epoxy resin e-44) 26 parts, water-based polyurethane (anionic water-based polyurethane) 28 parts, chitosan 7 parts, polystyrene microspheres 8 parts, nano-clay 4 parts, acrylic resin 14 parts, silica 4 parts, titanium dioxide (rutile) 3 parts, defoamer (dimethyl silicone oil) 0.8 parts, and foam inhibitor (hydrophobic silica) 0.7 parts.

[0133] A helmet impact protection water-based coating preparation method is also provided in the example, including the following steps:

[0134] S1: Using ultrasonic-assisted high-speed stirring technology, the water-based polyurethane and chitosan solution are mixed at an ultrasonic frequency of 30 kHz and a stirring speed of 1700 rpm for 50 minutes at a temperature of 30°C. The biocompatibility and antibacterial properties of chitosan are combined with the flexibility of water-based polyurethane to form a composite emulsion;

[0135] S2: Using layer-by-layer assembly technology, the acrylic resin molecules are adsorbed on the surface of the nano-clay layer by layer, and the pre-coating emulsion with a multi-layer structure is constructed by layer-by-layer assembly for 4 times at a pH value of 8 and a stirring speed of 800 rpm;

[0136] S3: The preheated epoxy resin is mixed with the diluent at a preheating temperature of 70°C for 24 minutes to reduce the viscosity. The silica and titanium dioxide are gradually added to ensure uniform dispersion of the components, and an epoxy resin base system is obtained.

[0137] S4: The composite emulsion and the pre-coating emulsion are mixed at a controlled stirring speed to avoid damaging the stability of the emulsion. The epoxy resin base system is slowly added to the mixed emulsion, and a dynamic mixer is used for mixing at a stirring speed of 3000 rpm for 50 minutes at a temperature of 40°C. This equipment can generate strong shear force and impact force through internal rotating elements while controlling the stirring speed, ensuring complete fusion of the components in a short time. Defoamer and foam inhibitor are added at the same time to reduce the generation of bubbles during the mixing process. Continuous stirring is carried out until the components are completely fused to form a uniform and stable coating system.

[0138] S5: The polystyrene microspheres are dispersed for 2 hours to ensure uniform dispersion. Under continuous stirring at a speed of 1300 rpm, the dispersed polystyrene microspheres are slowly added to the coating system in S4, and stirring is continued for 45 minutes to ensure uniform distribution of the polystyrene microspheres in the coating. A helmet impact protection water-based coating is obtained.

[0139] Example Four

[0140] A helmet impact protection water-based coating includes the following components by weight: epoxy resin (epoxy resin e-51) 30 parts, water-based polyurethane (anionic water-based polyurethane) 30 parts, chitosan 10 parts, polystyrene microspheres 10 parts, nano-clay 5 parts, acrylic resin 15 parts, silica 5 parts, titanium dioxide (titanium ore type) 3 parts, defoamer (dimethyl silicone oil) 1 part, and foam inhibitor (fatty alcohol) 1 part.

[0141] The preparation method of a helmet impact protection water-based coating is also given in the example, which includes the following steps:

[0142] S1: Using ultrasonic-assisted high-speed stirring technology, the water-based polyurethane and chitosan solution are mixed at an ultrasonic frequency of 40 kHz and a stirring speed of 2000 rpm for 60 minutes at a temperature of 40°C. The biocompatibility and antibacterial properties of chitosan are combined with the flexibility of water-based polyurethane to form a composite emulsion;

[0143] S2: Using layer-by-layer assembly technology, the acrylic resin molecules are adsorbed on the surface of the nano-clay layer by layer, and the pre-coating emulsion with a multi-layer structure is constructed by layer-by-layer assembly for 5 times at a pH value of 9 and a stirring speed of 1000 rpm;

[0144] S3: The preheated epoxy resin is mixed with the diluent at a preheating temperature of 80°C for 30 minutes to reduce the viscosity. The silica and titanium dioxide are gradually added to ensure uniform dispersion of the components, and an epoxy resin base system is obtained;

[0145] S4: The composite emulsion and the pre-coating emulsion are mixed at a controlled stirring speed to avoid damaging the stability of the emulsion. The epoxy resin base system is slowly added to the mixed emulsion, and a dynamic mixer is used for mixing at a stirring speed of 4000 rpm for 60 minutes at a temperature of 50°C. This equipment can generate strong shear force and impact force through internal rotating elements while controlling the stirring speed, ensuring complete fusion of the components in a short time. Defoamer and foam inhibitor are added at the same time to reduce the generation of bubbles during the mixing process. Continuous stirring is carried out until the components are completely fused to form a uniform and stable coating system;

[0146] S5: The polystyrene microspheres are subjected to dispersion treatment for 2 hours to ensure uniform dispersion. Under continuous stirring at a speed of 1500 rpm, the dispersed polystyrene microspheres are slowly added to the coating system in S4, and stirring is continued for 60 minutes to ensure uniform distribution of the polystyrene microspheres in the coating. A helmet impact protection water-based coating is obtained.

[0147] In the above embodiment one to embodiment four, in S2, the step of layer-by-layer assembly specifically includes:

[0148] S21: Preparation of nanoclay suspension: First, disperse the nanoclay in deionized water to form a stable suspension. The nanoclay has a negative charge due to the presence of hydroxyl or other anionic groups on its surface;

[0149] S22: Preparation of acrylic resin molecules: Select acrylic resin molecules with positive charges through chemical modification, so that they can be tightly bound to negatively charged nanoclay through electrostatic interaction;

[0150] S23: First layer assembly: Slowly add positively charged acrylic resin molecules to the nanoclay suspension. Due to electrostatic attraction, the acrylic resin molecules will adsorb to the surface of the nanoclay, forming a first layer of coating;

[0151] S24: Washing and separation: After completing the first layer assembly, perform a washing step by centrifugation to remove unadsorbed acrylic resin molecules, and then redisperse the nanoclay for the next layer assembly.

[0152] S25: Repeat the assembly process: Repeat steps S23 and S24 to alternately adsorb acrylic resin molecules until the desired multilayer structure is achieved.

[0153] Comparative example one

[0154] A method for preparing a helmet impact protection water-based coating, which is basically the same as embodiment four, except that step S4 specifically includes:

[0155] S41: First, pre-mix the composite emulsion with the pre-coating emulsion under controlled stirring speed. The key to this step is the control of stirring speed. A variable speed stirring technique is used, with an initial stirring speed of 400 rpm to ensure gentle fusion of the two emulsions and avoid high-speed stirring that can damage the stability of the emulsion. As the mixing progresses, gradually increase the stirring speed to 900 rpm to enhance the interaction between the emulsions and promote uniform mixing, but not exceeding the critical stirring speed of the emulsion stability;

[0156] S42: While pre-mixing, prepare the dynamic mixer. The device is equipped with rotating elements that can generate strong shear force and impact force while controlling the stirring speed. Preheat the dynamic mixer to ensure that its internal temperature is close to the temperature of the emulsion to be mixed, so as to reduce the influence of temperature difference on the mixing process;

[0157] S43: Slowly add the preheated epoxy resin base system to the dynamic mixer, and control the addition speed at 7% of the total amount per minute to avoid local concentration and uneven mixing caused by rapid addition. At the same time, the rotating elements of the dynamic mixer generate strong shear force and impact force to ensure that the epoxy resin and the pre-mixed emulsion are fully mixed in a short time;

[0158] S44: During the mixing process, bubbles may be generated due to the interaction of components and mechanical stirring. In order to reduce the generation of bubbles, defoaming agent and bubble inhibitor need to be added. When the amount of epoxy resin base system reaches 50% of the total amount, start to slowly add defoaming agent and bubble inhibitor, and the amount of each is 0.5% of the total amount, to ensure effective elimination and inhibition of bubble generation;

[0159] S45: During the entire mixing process, continuously monitor the viscosity, temperature and bubble situation of the mixed system, and adjust the stirring speed and mixing time according to the monitoring results to ensure that the components are fully mixed to form a uniform and stable coating system. The continuous stirring time is 60 minutes;

[0160] S46: When the components are fully mixed and the coating system reaches the expected uniformity and stability, stop stirring and post-treat the mixed coating system, such as filtering to remove possible impurities and insoluble particles, to ensure the purity and coating effect of the coating.

[0161] Comparative Example Two

[0162] A preparation method of a helmet impact protection water-based coating, which is basically the same as Example Four, except that step S5 specifically includes the following steps:

[0163] S51: The polystyrene microspheres are placed in a solvent containing a dispersant, such as deionized water or ethanol, with an initial concentration controlled at 10wt%. A high-speed disperser is used for initial dispersion, with a dispersion speed set at 3000rpm and a duration of 10 minutes to break the agglomeration between the microspheres. The initially dispersed polystyrene microsphere suspension is placed in an ultrasonic processor to further promote uniform dispersion of the microspheres using the cavitation effect of ultrasonic waves. The ultrasonic frequency is set at 40kHz and the processing time is 20 minutes, during which the temperature of the suspension is maintained at 40°C to prevent overheating. The dispersed polystyrene microspheres are evaluated for particle size distribution and dispersion state using an optical microscope or dynamic light scattering instrument to ensure that the microspheres achieve the desired uniform dispersion effect;

[0164] S52: Before adding the polystyrene microspheres, the coating system obtained in step S4 is pre-stirred at a speed of 800rpm to maintain uniformity and stability of the coating system. The dispersed polystyrene microsphere suspension is gradually added to the coating system by slow pumping under continuous stirring. The addition speed is controlled at 5% of the total amount per minute to avoid uneven mixing caused by excessive local concentration. During the addition process, the viscosity, gloss, and color changes of the coating system are monitored in real time to ensure good compatibility between the polystyrene microspheres and other components of the coating system;

[0165] S53: After all the polystyrene microspheres are added, the stirring speed is gradually increased to 1500rpm and continues for 60 minutes to ensure uniform distribution of the microspheres in the coating system. The stability of the stirred coating system is evaluated, including observing whether there is stratification, precipitation, or phase separation, and measuring the rheological properties of the coating by a rheometer. If the coating system has good stability, necessary post-processing is performed, including filtering to remove impurities and adjusting the pH value, followed by sealing and packaging to obtain the final helmet impact protection water-based coating product.

[0166] Comparative Example One

[0167] A method for preparing a helmet impact protection water-based coating, which is basically the same as Example Four, except that the nanoclay is removed and other components remain unchanged.

[0168] Comparative Example Two

[0169] A method for preparing a helmet impact protection water-based coating, which is basically the same as Example Four, except that in step S2, the nanoclay and acrylic resin are directly mixed without layer-by-layer assembly.

[0170] Comparative Example Three

[0171] A method for preparing a helmet impact protection waterborne coating, which is basically the same as that of Example Four, except that a dynamic mixer is not used in Step S4, but a conventional stirrer is used instead.

[0172] Comparative Example Four

[0173] A method for preparing a helmet impact protection waterborne coating, which is basically the same as that of Example Four, except that polystyrene microspheres are removed, and other components remain unchanged.

[0174] The waterborne coatings prepared in the above-mentioned Examples One to Four and Comparative Examples One to Four are detected as follows:

[0175] GB / T 1732-1993: Paint film impact resistance test method. This standard is used to test the impact resistance of paint film under high-speed gravity.

[0176] GB / T 9286-1998: Cross-hatch test for pigmented and clear coatings. This standard is used to evaluate the adhesion of the coating to the substrate.

[0177] GB / T 1771-2007: Determination of resistance to neutral salt spray of pigmented and clear coatings. This standard is used to test the corrosion resistance of the coating in a salt spray environment.

[0178] GB / T 5210-2006: Cross-hatch test for pigmented and clear coatings. This standard is used to test the corrosion resistance of the coating in a salt spray environment.

[0179] Specific detection method

[0180] Impact resistance test: According to GB / T 1732-1993 standard, use paint film impact tester to impact the coating, and observe whether the coating appears cracking, peeling and other phenomena.

[0181] Cross-hatch test: According to GB / T 9286-1998, draw a certain specification of grid on the surface of the coating, then paste with adhesive tape and quickly pull off, and observe the peeling of the coating in the grid.

[0182] Salt spray test: According to GB / T 1771-2007, place the painted sample in a salt spray test chamber to simulate marine or industrial salt spray environment, and test the corrosion resistance of the coating.

[0183] Pull-off adhesion test: According to GB / T 5210-2006, use a tensile testing machine to test the adhesion between the coating and the substrate.

[0184] The results are shown in Table 1 below:

[0185] Table 1

[0186]

[0187]

[0188] From the above Table 1, it can be directly and uniquely obtained that the impact resistance of the coating shows a gradually enhanced trend with the adjustment of the allocation ratio of each component and the optimization of the preparation process. Example Four shows the best impact resistance, which is related to the synergistic effect between each component and the formation of a uniform and stable coating system during the preparation process.

[0189] All examples reached the 0 level standard in the cross-hatch test, i.e., no peeling phenomenon. This indicates that the adhesion between the coating prepared by each example and the substrate is very strong, and the coating can remain intact during the cross-hatch test.

[0190] All examples can withstand 1000 hours without corrosion in the salt spray test. This shows that the coating prepared by each example has good corrosion resistance and can maintain the integrity and functionality of the coating in a harsh salt spray environment.

[0191] Pull-off adhesion: From the comparison of pull-off adhesion, it can be seen that the adhesion of the coating gradually increases with the optimization of the preparation process and the adjustment of the allocation ratio of each component. Examples Three and Four show the best adhesion performance.

[0192] In summary, the coatings prepared by all examples show good impact resistance, adhesion, and corrosion resistance. With the adjustment of the allocation ratio of each component and the optimization of the preparation process (such as ultrasonic frequency, stirring speed, mixing time, etc.), the performance of the coating shows a gradually enhanced trend.

[0193] Comparative Example One achieved higher impact resistance by optimizing the mixing process in S4 step, reaching 62 kg·cm. This shows that finer mixing process control, including variable speed stirring and the use of dynamic mixers, helps to improve the impact resistance of the coating. Comparative Example Two further improved the dispersion and addition method of polystyrene microspheres in S5 step, thereby obtaining higher impact resistance, reaching 65 kg·cm. This shows that the uniform dispersion of polystyrene microspheres and their good compatibility with the coating system are crucial for improving the impact resistance.

[0194] All examples and comparative examples reached the 0 level standard in the cross-hatch test, i.e., no peeling phenomenon. This indicates that the adhesion between the coating obtained under each preparation process and the substrate is very strong, and the coating can remain intact during the cross-hatch test.

[0195] Salt spray test: Example Four was able to withstand 1000 hours of salt spray testing without showing any signs of corrosion. Control Example One and Control Example Two both showed superior corrosion resistance, withstanding 1100 hours without any signs of corrosion. This indicates that by optimizing the mixing and dispersion process, not only did the physical properties of the coating (such as impact resistance) improve, but also its chemical stability, allowing it to last longer in harsh environments.

[0196] Pull-off adhesion: Example Four had a pull-off adhesion of 6.3 MPa, showing strong adhesion. Control Example One improved the adhesion to 7.1 MPa by improving the mixing step. This again demonstrates the importance of a fine mixing process in enhancing the bond between the coating and the substrate. Control Example Two further improved the adhesion to 7.5 MPa by optimizing the dispersion and addition process of the polystyrene microspheres. This indicates that the uniform distribution and good compatibility of the microspheres in the coating system have a significant impact on improving adhesion.

[0197] Reference Figures 1-5 In the other conditions are the same in Example Four and the comparative examples:

[0198] Impact resistance:

[0199] Example Four had an impact resistance of 55 kg·cm, showing good impact resistance. Control Example One (without nanoclay) had a significantly lower impact resistance of 40 kg·cm, indicating that nanoclay plays an important role in enhancing the impact resistance of the coating. Control Example Two (without layer-by-layer assembly) had a lower impact resistance of 45 kg·cm than Example Four, indicating that the layer-by-layer assembly technique helps to improve the impact resistance of the coating. Control Example Three (without dynamic mixer) had a slightly lower impact resistance of 48 kg·cm than Example Four, indicating that the use of a dynamic mixer has a positive impact on improving the performance of the coating. Control Example Four (without polystyrene microspheres) had the lowest impact resistance of 35 kg·cm, indicating that polystyrene microspheres are crucial for enhancing the impact resistance of the coating.

[0200] Crosshatch test:

[0201] Example Four and Control Example Three both reached the 0 level standard, indicating that the adhesion between the coating and the substrate was very strong. Control Example One and Control Example Four had higher crosshatch test levels of 3 and 2 respectively, indicating that removing nanoclay or polystyrene microspheres would significantly reduce the adhesion of the coating. Control Example Two was level 1, indicating that not performing layer-by-layer assembly would also affect the adhesion of the coating, but the impact was relatively small.

[0202] Salt spray test:

[0203] Example Four and Comparative Example Three both showed excellent corrosion resistance in the salt spray test, able to withstand 1000 hours without corrosion. Comparative Examples One, Two, and Four had poorer corrosion resistance, with corrosion occurring at 700 hours, 850 hours, and 650 hours, respectively, indicating that nano-clay, layer-by-layer assembly technology, and polystyrene microspheres all play important roles in improving the corrosion resistance of the coating.

[0204] Pull-off adhesion:

[0205] The pull-off adhesion of Example Four was 6.3 MPa, showing strong adhesion. The adhesion of Comparative Examples One, Two, Three, and Four were all lower than Example Four, with Comparative Example Four being the lowest (3.0 MPa), again demonstrating the important influence of components and preparation process on the performance of the coating.

[0206] In the present application, through the synergistic effect of the components, especially the energy absorption and self-repairing function of polystyrene microspheres, and the interpenetrating polymer network constructed by chitosan and waterborne polyurethane, the coating can effectively resist external impact and protect the internal structure of the helmet from damage.

[0207] The photocatalytic performance of titanium dioxide nanoparticles combined with the hardness of silicon dioxide, the core-shell structure nanoparticles constructed can enhance the self-cleaning ability of the coating, reduce the adhesion of pollutants, and maintain the cleanliness of the coating surface.

[0208] The dense pre-coating layer formed by nano-clay and acrylic resin improves the adhesion and durability of the coating, while the stability of the coating is guaranteed through fine preparation process and component selection, maintaining good performance in long-term use.

[0209] The elastomeric properties of polystyrene microspheres combined with the flexibility and wear resistance of chitosan and waterborne polyurethane, together construct a coating system that can absorb and disperse impact energy. This synergistic effect significantly improves the impact resistance of the coating, providing more effective protection for the helmet.

[0210] The introduction of nano materials such as nano-clay, silicon dioxide, and titanium dioxide not only enhances the hardness and wear resistance of the coating, but also synergistically improves the self-cleaning ability and antibacterial function of the coating through its special physical and chemical properties (such as photocatalytic activity).

[0211] To sum up, the energy absorption of the polystyrene microspheres is synergized with the biocompatibility and antibacterial function of the chitosan, and the flexibility and wear resistance of the waterborne polyurethane, which jointly construct a strong protection system; the pre-coating layer structure of the nano clay and the acrylic resin enhances the adhesion and stability of the paint; and the core-shell structure nanoparticles of the silicon dioxide and titanium dioxide endow the paint with excellent self-cleaning ability. The synergistic cooperation between these components not only improves the overall performance of the paint, but also makes it more adaptable to complex and variable use environment, providing all-round protection for the helmet.

[0212] The above merely describes the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and the inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A water-based helmet impact-resistant coating, characterized in that, The product comprises the following components in parts by weight: 20-30 parts epoxy resin, 20-30 parts waterborne polyurethane, 5-10 parts chitosan, 5-10 parts polystyrene microspheres, 3-5 parts nano-clay, 10-15 parts acrylic resin, 3-5 parts silica, 2-3 parts titanium dioxide, 0.5-1 part defoamer, and 0.5-1 part foam suppressant. The chitosan and the aqueous polyurethane form an interpenetrating polymer network; The preparation method of the water-based helmet impact-resistant coating includes the following steps: S1: Using ultrasonic-assisted high-speed stirring technology, waterborne polyurethane and chitosan solution are mixed to form a composite emulsion; S2: Disperse nano-clay in deionized water to form a stable suspension, slowly add acrylic resin, and use layer-by-layer assembly technology to adsorb acrylic resin molecules layer by layer on the surface of nano-clay to construct a pre-coated emulsion with a multi-layer structure. S3: Mix the preheated epoxy resin with the diluent to reduce the viscosity, and gradually add silica and titanium dioxide to ensure that each component is evenly dispersed to obtain the epoxy resin base system. S4: Under controlled stirring speed, the composite emulsion and the pre-coating emulsion are premixed using variable speed stirring technology. The initial stirring speed is set to 400 rpm, and the stirring speed is gradually increased to 900 rpm. While premixing, a dynamic mixer is prepared, which is equipped with a rotating element that can generate strong shear force and impact force while controlling the stirring speed. The dynamic mixer is preheated, and the preheated epoxy resin base system is slowly added to the dynamic mixer. While adding the epoxy resin base system, strong shear force and impact force are generated by the rotating element of the dynamic mixer. During the mixing process, when the amount of epoxy resin base system added reaches 50% of the total amount, defoamer and defoaming agent are slowly added. When all components are completely mixed, stirring is stopped, and the mixed coating system is post-treated. S5: Disperse the polystyrene microspheres, and then slowly add the dispersed polystyrene microspheres to the coating system in S4 under continuous stirring. Continue stirring for a period of time to ensure that the polystyrene microspheres are evenly distributed in the coating to obtain a water-based helmet impact protection coating.

2. The water-based helmet impact-resistant coating according to claim 1, characterized in that, The components include the following parts by weight: 23 parts epoxy resin, 26 parts waterborne polyurethane, 7 parts chitosan, 8 parts polystyrene microspheres, 4 parts nano clay, 12 parts acrylic resin, 4 parts silica, 2 parts titanium dioxide, 0.8 parts defoamer, and 0.7 parts foam suppressant.

3. The water-based helmet impact-resistant coating according to claim 1, characterized in that, The epoxy resin is one of epoxy resin E-44 or epoxy resin E-51, and the viscosity of the epoxy resin is 1000-1500 mPa·s; the waterborne polyurethane is anionic waterborne polyurethane with an average particle size of 50-100 nanometers; the chitosan has a molecular weight of 100,000-300,000; the polystyrene microspheres have an average particle size of 1-5 micrometers; the acrylic resin has a glass transition temperature of 30-50℃ and a weight-average molecular weight of 50,000-100,000; the titanium dioxide has a crystal form of rutile or anatase, and an average particle size of 0.2-0.4 micrometers; the defoamer is one of dimethyl silicone oil and polyether; the foam suppressant is one of hydrophobic silica and fatty alcohol.

4. A water-based helmet impact-resistant coating according to claim 1 or 2, characterized in that, The polystyrene microspheres have a core-shell structure with a gradient density distribution inside, and / or the surface of the polystyrene microspheres is modified with nanoscale silica particles.

5. A water-based helmet impact-resistant coating according to claim 1 or 2, characterized in that, The chitosan has been modified to introduce functional groups with the ability to chelate calcium ions into its molecular chain. The acrylic resin is a copolymer with a core-shell structure, wherein the core layer is a hard segment and the shell layer is a soft segment; The waterborne polyurethane has a star-shaped structure, with a rigid aromatic core and flexible aliphatic chain segments on the periphery. The surface of the titanium dioxide is modified with a thin film of photocatalytically active metal oxide using atomic layer deposition technology, and designed into a nano-shaped structure, including nanoflowers, nanotrees, or nanostars.

6. The water-based helmet impact-resistant coating according to claim 1, characterized in that, S5 specifically includes the following steps: S51: Place polystyrene microspheres in a solvent containing a dispersant and perform preliminary dispersion using a high-speed disperser. Place the pre-dispersed polystyrene microsphere suspension in an ultrasonic processor and use an optical microscope to evaluate the particle size distribution and dispersion state of the dispersed polystyrene microspheres to ensure that the microspheres achieve the required uniform dispersion effect. S52: Before adding polystyrene microspheres, pre-stir the coating system obtained in step S4. Under continuous stirring, gradually add the dispersed polystyrene microsphere suspension into the coating system by slow pumping. S53: After all the polystyrene microspheres are added, the stirring speed is gradually increased, and the stability of the stirred coating system is evaluated. This includes observing whether stratification, precipitation or phase separation occurs after standing, and measuring the rheological properties of the coating using a rheometer. If the coating system is stable, post-processing is performed, followed by sealing and packaging to obtain the final water-based helmet impact protection coating product.

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