Ultraviolet aging resistant light composite material and preparation method thereof

Abstract

The invention relates to an ultraviolet-aging-resistant light composite material, the material comprises a base layer and a functional coating, the base layer comprises a polymer matrix and an elastic microsphere low-temperature anti-cracking agent, and the functional coating comprises water-based resin and hollow anti-ultraviolet particles. The elastic microsphere low-temperature anti-cracking agent is of a multi-layer core-shell structure with a polybutadiene microgel inner core, a POE-g-GMA toughness middle layer and an organic-inorganic hybrid silicon shell, and the hollow anti-ultraviolet particles are hollow silicon dioxide microspheres with ZnO nanocrystals growing on the surfaces. The composite material has excellent lightweight characteristic and mechanical property, the low-temperature crack resistance and impact resistance of the material are remarkably improved by the elastic microsphere low-temperature anti-cracking agent through a multi-energy dissipation mechanism, and the hollow anti-ultraviolet particles provide lasting and efficient ultraviolet protection for a matrix through the synergistic effect of physical shielding and ultraviolet absorption.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a lightweight composite material resistant to ultraviolet aging and its preparation method. Background Technology

[0002] With the rapid development of aerospace, transportation and outdoor engineering equipment, lightweight, weather resistance and workability have become the core requirements of polymer composite materials. Outdoor engineering in high-altitude meadow areas has particularly stringent requirements for material performance, requiring materials to have multiple characteristics such as lightweight and easy installation, resistance to ultraviolet aging, resistance to low-temperature cracking and recyclability. However, traditional polymer materials are difficult to meet these comprehensive performance indicators.

[0003] While general-purpose resins such as polyethylene (PE), polypropylene (PP), and polyester (PET) offer excellent mechanical properties and economic benefits, they have significant limitations in high-altitude meadow applications. On the one hand, the molecular chains of polyolefins and polyesters are sensitive to ultraviolet light and are prone to photo-oxidative degradation under long-term strong ultraviolet irradiation, leading to discoloration, powdering, cracking, and a sharp decline in mechanical properties, thus shortening their service life. On the other hand, the low-temperature alternating environment with large diurnal temperature differences in this region causes the materials to repeatedly undergo thermal expansion and contraction, resulting in internal stress concentration, reduced toughness, and loss of load-bearing capacity.

[0004] To improve the performance defects of single polymers, blending modification has become a common strategy, such as introducing flexible polycaprolactone (PCL) into the PE matrix to enhance its toughness. However, simple physical blending does not fundamentally solve the inherent problem of weak UV aging resistance. Technicians often use the addition of small-molecule UV absorbers or light stabilizers to improve weather resistance, but these additives are prone to migration, volatilization, and extraction. Under long-term outdoor use or exposure to rain and snow, their protective effect will rapidly decline, failing to provide lasting protection. In terms of crack resistance, although the matrix can be toughened by adding elastomers or rubber particles, these additives often have poor compatibility with the matrix, or while sacrificing the rigidity and strength of the material, they are also difficult to effectively inhibit the initiation and propagation of microcracks under low-temperature alternating stress.

[0005] Therefore, there is an urgent need in this field for a material design and preparation scheme that synergistically addresses lightweight, UV-resistant, and low-temperature crack-resistant properties. This is of vital importance for promoting the development of green and rapid construction technologies in harsh environments such as high-altitude meadow areas. Summary of the Invention

[0006] The technical problem to be solved: The purpose of this invention is to provide a lightweight composite material resistant to ultraviolet aging and its preparation method, including a base layer and a functional coating. The base layer includes a polymer matrix and an elastic microsphere low-temperature crack-resistant agent. The functional coating includes an aqueous resin and hollow ultraviolet-resistant particles. The elastic microsphere low-temperature crack-resistant agent significantly improves the low-temperature crack resistance and impact resistance of the material through multiple energy dissipation mechanisms. The hollow ultraviolet-resistant particles provide durable and efficient ultraviolet protection to the matrix through the synergistic effect of physical shielding and ultraviolet absorption.

[0007] Technical solution: A lightweight composite material resistant to ultraviolet aging and its preparation method: The composite material includes a base layer and a functional coating. The base layer contains a polymer matrix and an elastic microsphere low-temperature crack-resistant agent. The functional coating contains an aqueous resin and hollow ultraviolet-resistant particles.

[0008] Furthermore, the core of the elastic microsphere low-temperature crack-resistant agent is polybutadiene microgel, the outer shell is an organic-inorganic hybrid silicon layer, and a tough intermediate layer is provided between the core and the outer shell. The hollow UV-resistant particles are hollow silica microspheres with ZnO nanocrystals on the surface.

[0009] Furthermore, the average particle size of the elastic microsphere low-temperature crack-resistant agent is 1.2~2.5μm, the average particle size of the hollow UV-resistant particles is 0.6~1μm, and the thickness of the functional coating is 20~100μm.

[0010] The method for preparing the above-mentioned UV-resistant lightweight composite material is characterized by comprising the following steps: S1. Dry 60-80 parts of polyethylene and 20-40 parts of polycaprolactone, add 10-15 parts of elastic microsphere low-temperature crack-resistant agent and 0.5-2 parts of additives, and mix at high speed until uniform to obtain a premix. S2. The premixed material is melt-blended and extruded in a twin-screw extruder, and then molded by hot press to obtain a composite board; S3. Mix 5-20 parts of hollow UV-resistant granules, 50-70 parts of waterborne polyurethane resin, 0.1-0.5 parts of leveling agent and 30-50 parts of water at high speed with shearing, spray the mixture onto the surface of the composite board, allow it to level, and cure it at 60-80℃ to obtain a lightweight composite material resistant to UV aging.

[0011] Furthermore, the leveling agent in step S3 is BYK-333.

[0012] Furthermore, the preparation method of the elastic microsphere low-temperature crack-resistant agent includes the following steps: S11. Butadiene monomer and divinylbenzene in a mass ratio of 95:5 to 85:15 are added to an aqueous solution of sodium dodecyl sulfate, and the mixture is emulsified by high-speed shearing to obtain an emulsion; S12. After heating the emulsion to 65~75℃, potassium persulfate aqueous solution is added in batches and reacted for 6~12h. After the reaction solution is cooled, 50% ethanol aqueous solution is added. The precipitate is centrifuged, washed, and dried at low temperature to obtain low cross-linked polybutadiene microgel. S13. Dissolve POE-g-GMA in an organic solvent, disperse the microgel in the solution, and the mass ratio of POE-g-GMA to microgel is 1:5~1:2. React at 80~100℃ for 2~6h. After the reaction, cool and pour into ethanol, filter and wash, and vacuum dry to obtain the intermediate product. S14. Disperse the intermediate product, add tetraethyl orthosilicate and silane coupling agent in a mass ratio of 1:0.2~1:1, adjust the pH to 10 with ammonia, hydrolyze and condense, filter and wash, and vacuum dry to obtain the elastic microsphere low-temperature crack-resistant agent.

[0013] Furthermore, the preparation method of hollow UV-resistant particles includes the following steps: S21. Add 1-3 wt% of an aqueous solution of polydiallyldimethylammonium chloride (PDDA) to the polystyrene microsphere dispersion, stir to adsorb, and filter to obtain polystyrene microspheres with positively charged surfaces; S22. Disperse positively charged polystyrene microspheres in ethanol / water at a volume ratio of 4:1, add ammonia, add tetraethyl orthosilicate (a silicon source precursor), react at 30-40°C, centrifuge and wash, and calcine at 500-600°C for 2-4 hours to obtain hollow silica microspheres. S23. Disperse hollow silica microspheres in water, add zinc acetate dihydrate and urea, wherein the mass ratio of silica, zinc acetate dihydrate and urea is 1: (0.5~2): (1~4), and perform hydrothermal reaction at 90~120℃ for 4~8h. After centrifugation, washing and drying, hollow UV-resistant particles are obtained.

[0014] Furthermore, the additives in step S1 include antioxidants and lubricants.

[0015] Furthermore, the antioxidant is oxidant 1010, and the lubricant is zinc stearate.

[0016] Furthermore, in step S2, the temperature of each section of the twin-screw extruder is 160~220℃, the screw speed is 100~300r / min, and the compression molding is carried out by hot pressing and holding at 170~190℃ and 5~15MPa for 5~15min, followed by holding the pressure and cooling to 40~60℃ before demolding.

[0017] Furthermore, in step S13, the organic solvent is toluene or xylene, and the silane coupling agent is KH-550 or KH-570.

[0018] Beneficial effects: The lightweight composite material resistant to ultraviolet aging and its preparation method of the present invention have the following advantages: The core of the elastic microsphere low-temperature crack-resistant agent in this invention is a polybutadiene microgel, and the outer shell is an organic-inorganic hybrid silicon layer. A tough intermediate layer is provided between the core and the outer shell. The flexible polybutadiene microgel core acts as the main stress concentration point and elastomer, and can absorb a large amount of energy through its own deformation when the material is subjected to low temperature or external impact. The ethylene-octene copolymer grafted glyceryl methacrylate (POE-g-GMA) intermediate layer not only forms chemical bonds with the core and outer shell through the glycidyl methacrylate (GMA) functional groups, enhancing the interfacial bonding force, but its own polyolefin elastomer segments also provide excellent toughness buffering. The organic-inorganic hybrid silicon outer shell ensures the structural integrity of the microspheres during processing and can form good bonding with the polymer matrix. When microcracks occur in the matrix, this core-shell structure can dissipate energy through plastic deformation and other means, improving the crack resistance and impact resistance of the composite material in low-temperature environments.

[0019] The hollow UV-resistant particles of this invention construct a triple synergistic protection mechanism of physical shielding, optical reflection, and UV absorption, achieving efficient and long-lasting protection for the polymer matrix. The hollow structure of the silica microspheres can effectively refract and diffusely reflect incident ultraviolet light, reducing the energy of ultraviolet light directly acting on the matrix resin. The ZnO nanocrystals grown on its surface are a wide bandgap semiconductor material that can strongly absorb ultraviolet light in the UVA and UVB bands through its own electronic transitions, converting light energy into heat energy for dissipation. In addition, the hollow silica microspheres anchor the ZnO nanocrystals on its surface, effectively preventing the agglomeration of nanoparticles and increasing the effective action area.

[0020] The hollow UV-resistant particles in the functional coating of this invention contain still air that acts as an excellent thermal insulator, effectively blocking heat conduction and thus reducing the overall thermal conductivity of the material. This characteristic enables the material to mitigate internal temperature fluctuations caused by solar radiation or drastic changes in ambient temperature during outdoor applications, thereby improving structural dimensional stability.

[0021] The lightweighting of this invention does not come at the expense of mechanical properties. The elastic microsphere low-temperature crack-resistant agent and hollow UV-resistant particles used are both low-density fillers. While the elastic microsphere low-temperature crack-resistant agent toughens the material, its rigid shell helps maintain the modulus of the material. The hollow silica microspheres themselves have a certain rigidity, which can play a reinforcing role. This allows the material to maintain good rigidity, strength and creep resistance while reducing weight, thus meeting the basic load-bearing requirements of engineering materials. Detailed Implementation

[0022] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: The polystyrene microspheres were purchased from Zhiyi Technology, with a particle size of 300~800nm.

[0023] Example 1

[0024] A method for preparing a lightweight composite material resistant to ultraviolet aging, characterized by comprising the following steps: S1. Dry 60 parts of polyethylene and 40 parts of polycaprolactone, add 10 parts of elastic microsphere low-temperature crack-resistant agent, 0.5 parts of antioxidant 1010 and 0.5 parts of lubricant zinc stearate, mix at high speed to obtain a uniform premix; S2. The premixed material is melt-blended and extruded in a twin-screw extruder. The temperatures of each section are set as follows: Zone 1 165℃, Zone 2 175℃, Zone 3 185℃, Zone 4 195℃, and Die Head 205℃. The screw speed is 200 r / min. After obtaining the composite masterbatch, it is placed in a hot press mold and hot-pressed at 170℃ and 15MPa for 15 minutes. Then, it is held under pressure and cooled to below 50℃ before demolding to obtain the composite board. S3. Mix 20 parts of hollow UV-resistant granules, 50 parts of waterborne polyurethane resin, 0.1 parts of leveling agent BYK-333 and 30 parts of water at high speed under shear and stir. Spray the mixture onto the surface of the composite board, allow it to level, and cure at 60℃ for 30 minutes to obtain a lightweight composite material with a coating thickness of 20μm that resists UV aging.

[0025] The preparation method of the elastic microsphere low-temperature crack-resistant agent is as follows: S11. Add 47.5 g of butadiene monomer and 2.5 g of divinylbenzene to a 1.5 wt% sodium dodecyl sulfate aqueous solution, and emulsify by high-speed shearing for 20 min to obtain an emulsion; S12. After the emulsion is heated to 75℃, 50 mL of 1.5 wt% potassium persulfate aqueous solution is added in batches and the reaction is carried out for 10 h. After the reaction solution is cooled, an equal volume of 50% ethanol aqueous solution is added. The precipitate is centrifuged, washed, and dried at low temperature to obtain low cross-linked polybutadiene microgel. S13. Dissolve 2g of POE-g-GMA in 100mL of toluene, disperse 10g of microgel in the solution, react at 80℃ for 6h, cool after reaction and pour into 500mL of ethanol to precipitate the product, filter, wash and vacuum dry to obtain the intermediate product. S14. Disperse 10g of intermediate product, add 2g of tetraethyl orthosilicate and 2g of silane coupling agent, adjust the pH to 10 with ammonia water, hydrolyze and condense, filter and wash, vacuum dry to obtain a low-temperature crack-resistant agent with elastic microspheres of average particle size of 1.2μm.

[0026] The preparation method of hollow UV-resistant particles includes the following steps: S21. Add an equal volume of 1 wt% PDDA aqueous solution to 200 mL of 2 wt% polystyrene microsphere dispersion, stir and adsorb for 20 min, and filter to obtain polystyrene microspheres with positively charged surfaces. S22. Positively charged polystyrene microspheres were dispersed in 160 mL of ethanol / water with a volume ratio of 4:1, ammonia was added dropwise until the pH was 10, and tetraethyl orthosilicate, a silicon source precursor, was added dropwise. After reacting at 30 °C, the mixture was centrifuged, washed, and calcined at 500 °C for 4 h to obtain hollow silica microspheres. S23. Disperse 1g of hollow silica microspheres in 80mL of water, add 2g of zinc acetate dihydrate and 4g of urea, and perform a hydrothermal reaction at 90℃ for 8h. After centrifugation, washing and drying, hollow UV-resistant particles with an average particle size of 1μm are obtained.

[0027] Example 2

[0028] A method for preparing a lightweight composite material resistant to ultraviolet aging, characterized by comprising the following steps: S1. Dry 80 parts of polyethylene and 20 parts of polycaprolactone, add 15 parts of elastic microsphere low-temperature crack-resistant agent, 1 part of antioxidant 1010 and 1 part of lubricant zinc stearate, mix at high speed to obtain a uniform premix. S2. The premixed material is melt-blended and extruded in a twin-screw extruder. The temperatures of each section are set as follows: Zone 1 165℃, Zone 2 175℃, Zone 3 185℃, Zone 4 195℃, and Die Head 205℃. The screw speed is 200 r / min. After obtaining the composite masterbatch, it is placed in a hot press mold and hot-pressed at 190℃ and 5MPa for 5 minutes. Then, it is held under pressure and cooled to below 60℃ before demolding to obtain the composite board. S3. Mix 5 parts of hollow UV-resistant granules, 70 parts of waterborne polyurethane resin, 0.5 parts of leveling agent BYK-333 and 50 parts of water at high speed under shear and stir. Spray the mixture onto the surface of the composite board, allow it to level, and cure at 80℃ for 30 minutes to obtain a lightweight composite material with a coating thickness of 100μm that resists UV aging.

[0029] The preparation method of the elastic microsphere low-temperature crack-resistant agent is as follows: S11. Add 42.5 g of butadiene monomer and 7.5 g of divinylbenzene to a 1.5 wt% sodium dodecyl sulfate aqueous solution, and emulsify by high-speed shearing for 20 min to obtain an emulsion; S12. After the emulsion is heated to 65℃, 60 mL of 2.5wt% potassium persulfate aqueous solution is added in batches and the reaction is carried out for 10 h. After the reaction solution is cooled, an equal volume of 50% ethanol aqueous solution is added. The precipitate is centrifuged, washed, and dried at low temperature to obtain low cross-linked polybutadiene microgel. S13. Dissolve 5g of POE-g-GMA in 100mL of toluene, disperse 10g of microgel in the solution, react at 100℃ for 2h, cool after reaction and pour into 500mL of ethanol to precipitate the product, filter, wash and vacuum dry to obtain the intermediate product. S14. Disperse 10g of intermediate product, add 3g of tetraethyl orthosilicate and 0.6g of silane coupling agent (mass ratio 1:0.2), adjust pH to 10 with ammonia, hydrolyze and condense, filter and wash, vacuum dry to obtain a low-temperature crack-resistant agent with elastic microspheres of average particle size of 2.5μm.

[0030] The preparation method of hollow UV-resistant particles includes the following steps: S21. Add an equal volume of 3wt% PDDA aqueous solution to 200mL of 2wt% polystyrene microsphere dispersion, stir and adsorb for 20min, and filter to obtain polystyrene microspheres with positively charged surfaces. S22. Positively charged polystyrene microspheres were dispersed in 160 mL of ethanol / water with a volume ratio of 4:1, ammonia was added dropwise until the pH was 10, and tetraethyl orthosilicate, a silicon source precursor, was added dropwise. After reacting at 40 °C, the mixture was centrifuged, washed, and calcined at 600 °C for 2 h to obtain hollow silica microspheres. S23. Disperse 1g of hollow silica microspheres in 80mL of water, add 0.5g of zinc acetate dihydrate and 1g of urea, and perform a hydrothermal reaction at 120℃ for 4h. After centrifugation, washing and drying, hollow UV-resistant particles with an average particle size of 0.6μm are obtained.

[0031] Example 3

[0032] A method for preparing a lightweight composite material resistant to ultraviolet aging, characterized by comprising the following steps: S1. Dry 70 parts of polyethylene and 30 parts of polycaprolactone, add 12 parts of elastic microsphere low-temperature crack-resistant agent, 0.5 parts of antioxidant 1010 and 0.5 parts of lubricant zinc stearate, mix at high speed to obtain a uniform premix; S2. The premixed material is melt-blended and extruded in a twin-screw extruder. The temperatures of each section are set as follows: Zone 1 165℃, Zone 2 175℃, Zone 3 185℃, Zone 4 195℃, and Die Head 205℃. The screw speed is 200 r / min. After obtaining the composite masterbatch, it is placed in a hot press mold and hot-pressed at 180℃ and 10MPa for 10 minutes. Then, it is held under pressure and cooled to below 50℃ before demolding to obtain the composite board. S3. Mix 15 parts of hollow UV-resistant granules, 60 parts of waterborne polyurethane resin, 0.3 parts of leveling agent BYK-333 and 40 parts of water at high speed under shear and stir. Spray the mixture onto the surface of the composite board, allow it to stand and level, and cure at 70℃ for 30 minutes to obtain a lightweight composite material with a coating thickness of 50μm that resists UV aging.

[0033] The preparation method of the elastic microsphere low-temperature crack-resistant agent is as follows: S11. Add 45g of butadiene monomer and 5g of divinylbenzene to a 1.5wt% sodium dodecyl sulfate aqueous solution, and emulsify by high-speed shearing for 20min to obtain an emulsion; S12. After the emulsion is heated to 70℃, 50 mL of 2wt% potassium persulfate aqueous solution is added in batches and the reaction is carried out for 10 h. After the reaction solution is cooled, an equal volume of 50% ethanol aqueous solution is added. The precipitate is centrifuged, washed, and dried at low temperature to obtain low cross-linked polybutadiene microgel. S13. Dissolve 3.3g POE-g-GMA in 100mL toluene, disperse 10g microgel in the solution, react at 90℃ for 4h, cool after reaction and pour into 500mL ethanol to precipitate the product, filter, wash and vacuum dry to obtain intermediate product; S14. Disperse 10g of intermediate product, add 2g of tetraethyl orthosilicate and 1g of silane coupling agent, adjust the pH to 10 with ammonia water, hydrolyze and condense, filter and wash, vacuum dry to obtain a low-temperature crack-resistant agent with elastic microspheres of average particle size of 1.5μm.

[0034] The preparation method of hollow UV-resistant particles includes the following steps: S21. Add an equal volume of 2wt% PDDA aqueous solution to 200mL of 3wt% polystyrene microsphere dispersion, stir and adsorb for 20min, and filter to obtain polystyrene microspheres with positively charged surfaces. S22. Positively charged polystyrene microspheres were dispersed in 160 mL of ethanol / water with a volume ratio of 4:1, ammonia was added dropwise until the pH was 10, and tetraethyl orthosilicate, a silicon source precursor, was added dropwise. After reacting at 35 °C, the mixture was centrifuged, washed, and calcined at 550 °C for 3 h to obtain hollow silica microspheres. S23. Disperse 1g of hollow silica microspheres in 80mL of water, add 1.2g of zinc acetate dihydrate and 2.5g of urea, and perform a hydrothermal reaction at 110℃ for 6h. After centrifugation, washing and drying, hollow UV-resistant particles with an average particle size of 0.8μm are obtained.

[0035] Example 4

[0036] A method for preparing a lightweight composite material resistant to ultraviolet aging, characterized by comprising the following steps: S1. Dry 70 parts of polyethylene and 30 parts of polycaprolactone, add 12 parts of elastic microsphere low-temperature crack-resistant agent, 0.5 parts of antioxidant 1010 and 0.5 parts of lubricant zinc stearate, mix at high speed to obtain a uniform premix; S2. The premixed material is melt-blended and extruded in a twin-screw extruder. The temperatures of each section are set as follows: Zone 1 165℃, Zone 2 175℃, Zone 3 185℃, Zone 4 195℃, and Die Head 205℃. The screw speed is 200 r / min. After obtaining the composite masterbatch, it is placed in a hot press mold and hot-pressed at 180℃ and 10MPa for 10 minutes. Then, it is held under pressure and cooled to below 50℃ before demolding to obtain the composite board. S3. Mix 15 parts of hollow UV-resistant granules, 60 parts of waterborne polyurethane resin, 0.3 parts of leveling agent BYK-333 and 40 parts of water at high speed under shear and stir. Spray the mixture onto the surface of the composite board, allow it to stand and level, and cure at 70℃ for 30 minutes to obtain a lightweight composite material with a coating thickness of 50μm that resists UV aging.

[0037] The preparation method of the elastic microsphere low-temperature crack-resistant agent is as follows: S11. Add 45g of butadiene monomer and 5g of divinylbenzene to a 1.5wt% sodium dodecyl sulfate aqueous solution, and emulsify by high-speed shearing for 20min to obtain an emulsion; S12. After the emulsion is heated to 70℃, 50 mL of 2wt% potassium persulfate aqueous solution is added in batches and the reaction is carried out for 10 h. After the reaction solution is cooled, an equal volume of 50% ethanol aqueous solution is added. The precipitate is centrifuged, washed, and dried at low temperature to obtain low cross-linked polybutadiene microgel. S13. Dissolve 3.3g POE-g-GMA in 100mL toluene, disperse 10g microgel in the solution, react at 90℃ for 4h, cool after reaction and pour into 500mL ethanol to precipitate the product, filter, wash and vacuum dry to obtain intermediate product; S14. Disperse 10g of intermediate product, add 2g of tetraethyl orthosilicate and 1g of silane coupling agent, adjust the pH to 10 with ammonia water, hydrolyze and condense, filter and wash, vacuum dry to obtain a low-temperature crack-resistant agent with elastic microspheres of average particle size of 1.5μm.

[0038] The preparation method of hollow UV-resistant particles includes the following steps: S21. Add an equal volume of 2wt% PDDA aqueous solution to 200mL of 3wt% polystyrene microsphere dispersion, stir and adsorb for 20min, and filter to obtain polystyrene microspheres with positively charged surfaces. S22. Positively charged polystyrene microspheres were dispersed in 160 mL of ethanol / water with a volume ratio of 4:1, ammonia was added dropwise until the pH was 10, and tetraethyl orthosilicate, a silicon source precursor, was added dropwise. After reacting at 35 °C, the mixture was centrifuged, washed, and calcined at 550 °C for 3 h to obtain hollow silica microspheres. S23. Disperse 1g of hollow silica microspheres in 80mL of water, add 2g of zinc acetate dihydrate and 1g of urea, and perform a hydrothermal reaction at 110℃ for 6h. After centrifugation, washing and drying, hollow UV-resistant particles with an average particle size of 0.9μm are obtained.

[0039] Example 5

[0040] A method for preparing a lightweight composite material resistant to ultraviolet aging, characterized by comprising the following steps: S1. Dry 70 parts of polyethylene and 30 parts of polycaprolactone, add 12 parts of elastic microsphere low-temperature crack-resistant agent, 0.5 parts of antioxidant 1010 and 0.5 parts of lubricant zinc stearate, mix at high speed to obtain a uniform premix; S2. The premixed material is melt-blended and extruded in a twin-screw extruder. The temperatures of each section are set as follows: Zone 1 165℃, Zone 2 175℃, Zone 3 185℃, Zone 4 195℃, and Die Head 205℃. The screw speed is 200 r / min. After obtaining the composite masterbatch, it is placed in a hot press mold and hot-pressed at 180℃ and 10MPa for 10 minutes. Then, it is held under pressure and cooled to below 50℃ before demolding to obtain the composite board. S3. Mix 15 parts of hollow UV-resistant granules, 60 parts of waterborne polyurethane resin, 0.3 parts of leveling agent BYK-333 and 40 parts of water at high speed under shear and stir. Spray the mixture onto the surface of the composite board, allow it to stand and level, and cure at 70℃ for 30 minutes to obtain a lightweight composite material with a coating thickness of 50μm that resists UV aging.

[0041] The preparation method of the elastic microsphere low-temperature crack-resistant agent is as follows: S11. Add 45g of butadiene monomer and 5g of divinylbenzene to a 1.5wt% sodium dodecyl sulfate aqueous solution, and emulsify by high-speed shearing for 20min to obtain an emulsion; S12. After the emulsion is heated to 70℃, 50 mL of 2wt% potassium persulfate aqueous solution is added in batches and the reaction is carried out for 10 h. After the reaction solution is cooled, an equal volume of 50% ethanol aqueous solution is added. The precipitate is centrifuged, washed, and dried at low temperature to obtain low cross-linked polybutadiene microgel. S13. Dissolve 3.3g POE-g-GMA in 100mL toluene, disperse 10g microgel in the solution, react at 90℃ for 4h, cool after reaction and pour into 500mL ethanol to precipitate the product, filter, wash and vacuum dry to obtain intermediate product; S14. Disperse the intermediate product 10, add 2g of tetraethyl orthosilicate and 1g of silane coupling agent, adjust the pH to 10 with ammonia, hydrolyze and condense, filter and wash, and vacuum dry to obtain a low-temperature crack-resistant agent with elastic microspheres of average particle size of 1.5μm.

[0042] The preparation method of hollow UV-resistant particles includes the following steps: S21. Add an equal volume of 2wt% PDDA aqueous solution to 200mL of 3wt% polystyrene microsphere dispersion, stir and adsorb for 20min, and filter to obtain polystyrene microspheres with positively charged surfaces. S22. Positively charged polystyrene microspheres were dispersed in 160 mL of ethanol / water with a volume ratio of 4:1, ammonia was added dropwise until the pH was 10, and tetraethyl orthosilicate, a silicon source precursor, was added dropwise. After reacting at 35 °C, the mixture was centrifuged, washed, and calcined at 550 °C for 3 h to obtain hollow silica microspheres. S23. Disperse 1g of hollow silica microspheres in 80mL of water, add 1.2g of zinc acetate dihydrate and 2.5g of urea, and perform a hydrothermal reaction at 110℃ for 6h. After centrifugation, washing and drying, hollow UV-resistant particles with an average particle size of 0.8μm are obtained.

[0043] Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that no low-temperature crack-resistant agent for elastic microspheres was added during the preparation of the composite material in this comparative example, and the other parameters are the same as in Example 3.

[0044] Comparative Example 2 The difference between Comparative Example 2 and Example 3 is that the composite material of this comparative example is not coated with an anti-UV particle coating during preparation, and the other parameters are the same as those in Example 3.

[0045] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that: in this comparative example, ordinary nitrile rubber particles of the same size are used to replace the low-temperature crack-resistant agent of elastic microspheres in Example 3, and the remaining steps are the same as in Example 3.

[0046] Comparative Example 4 The difference between Comparative Example 4 and Example 3 is that in the preparation of elastic microspheres, step S13 is skipped in this comparative example, and the hybrid silicon shell is directly wrapped on the polybutadiene microgel. The remaining steps are the same as in Example 3.

[0047] Comparative Example 5 The difference between Comparative Example 5 and Example 3 is that: in this comparative example, an equal amount of nano ZnO powder is used to replace the hollow UV-resistant particles in Example 3, and the remaining steps are the same as in Example 3.

[0048] Comparative Example 6 The difference between Comparative Example 6 and Example 3 is that: in this comparative example, an equal amount of SiO2 particles are used to replace the hollow UV-resistant particles in Example 3, and the remaining steps are the same as in Example 3.

[0049] Comparative Example 7 The difference between Comparative Example 7 and Example 3 is that in the preparation of hollow UV-resistant particles, step S23 is skipped in this comparative example, and hollow silica microspheres are only prepared for functional coating. The remaining steps are the same as in Example 3.

[0050] Comparative Example 8 The difference between Comparative Example 8 and Example 3 is that only 80 parts of polyethylene were used for the base layer, without the addition of PCL, and the remaining steps were the same as in Example 3.

[0051] Comparative Example 9 The difference between Comparative Example 9 and Example 3 is that, based on the formulation of Example 3, the amount of elastic microspheres and hollow UV-resistant particles added in this comparative example is increased to 40 parts.

[0052] Comparative Example 10 Comparative Example 10 is a general-purpose PE board material on the market that has not undergone special weather-resistant modification.

[0053] Testing: Mechanical property testing was conducted according to GB / T 1040.2-2022. The specimen specifications were: total length ≥ 150 mm, gauge length 50.0 mm ± 0.5 mm, width 10.0 mm ± 0.2 mm, and preferred thickness 4.0 mm. The specimen was vertically clamped in the fixture of a universal testing machine and subjected to a uniform tensile load of 50 mm / min until fracture. Tensile strength, elongation at break, and tensile modulus were recorded and calculated. Low-temperature crack resistance and cold resistance testing were conducted according to GB / T 1843-2008 at -30℃. UV aging resistance testing was conducted according to GB / T 16422.3-2022, using a UVB-313 lamp with an irradiance of 0.76 W / m². 2 The total aging time was 500 hours. After aging, the tensile strength was tested and the strength retention rate was calculated. The color change (ΔE) was measured using a colorimeter.

[0054] Table 1 Mechanical property tests and density

[0055] Referring to Table 1, the embodiments of the present invention illustrate the balance achieved between high toughness and lightweight. This is because the PE / PCL matrix provides basic mechanical strength and toughness, while the core-shell structured elastic microsphere low-temperature crack-resistant agent acts as a stress concentration point. Through the deformation of its polybutadiene core, the toughness buffer of the POE-g-GMA intermediate layer, and the rigid support of the hybrid silicon shell, it achieves efficient energy dissipation, thereby improving the material's low-temperature impact resistance. The introduction of hollow UV-resistant particles provides UV protection, and their low-density characteristics and inherent rigidity contribute to the material's lightweight nature while maintaining good mechanical properties. Comparative Example 1, without the addition of the elastic microsphere low-temperature crack-resistant agent, shows a sharp decrease in impact strength and elongation at break. Comparative Example 3, using ordinary nitrile rubber particles instead, demonstrates that simple elastomer particles have poor compatibility with the matrix and weak interfacial bonding. The lack of an effective energy dissipation mechanism in Comparative Example 4, which lacked the POE-g-GMA interlayer during microsphere preparation, resulted in a decline in performance, demonstrating the importance of POE-g-GMA in enhancing the interfacial bonding between the core and the rigid shell. The absence of this layer weakens stress transfer efficiency and reduces the toughening effect. Comparative Example 8, which did not add the PCL flexible component, resulted in a decrease in material toughness, indicating that the introduction of PCL is crucial for improving the brittleness of the PE matrix and enhancing its plastic deformation capacity. Comparative Example 9, which increased the addition amount of both functional fillers to 40 parts, resulted in a comprehensive deterioration of tensile strength, elongation at break, and impact strength. This is because excessive filler disrupts the continuity of the polymer matrix, forming stress defect points. It may also lead to agglomeration due to dispersion difficulties, thus becoming a weak link in the material. This demonstrates the necessity of "appropriate" filler for achieving optimal performance.

[0056] Table 2 UV aging resistance test

[0057] Referring to Table 2, after 500 hours of accelerated UV aging, Example 3 exhibited superior UV aging resistance, with significantly better tensile strength retention and color change than the comparative example. This is mainly due to the triple synergistic protection mechanism of physical shielding, optical reflection, and UV absorption constructed by the hollow anti-UV particles in the functional coating: the hollow SiO2 microspheres effectively reflect and scatter ultraviolet light; the ZnO nanocrystals grown on their surface, as wide-bandgap semiconductors, strongly absorb UVA and UVB ultraviolet light and convert it into heat energy; at the same time, the hollow structure anchors the ZnO nanocrystals, preventing their aggregation and increasing the effective working area. In Comparative Example 2, the lack of an anti-UV coating resulted in severe performance degradation. The polymer matrix, lacking coating protection, was directly exposed to ultraviolet light, leading to chain breakage and cross-linking, resulting in loss of mechanical properties and severe yellowing. In Comparative Example 5, pure ZnO powder was used, but the nanoparticles easily agglomerated, reducing the effective contact area. Furthermore, the agglomerates could become stress defect points, leading to a decrease in mechanical properties and significant color changes. Comparative Example 6 demonstrates that hollow structures have a significant advantage over solid particles in enhancing light reflection / scattering. Comparative Example 7 confirms that relying solely on the physical shielding and reflection of hollow SiO2 lacks the UV absorption capacity of ZnO, making it impossible to achieve comprehensive and efficient UV blocking. Comparative Example 10 shows that the commercially available unmodified PE board exhibited the most severe aging, highlighting the significant durability advantage of the material of this invention under harsh UV environments.

[0058] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A lightweight composite material resistant to ultraviolet aging, characterized in that: The composite material includes a base layer and a functional coating. The base layer comprises a polymer matrix and an elastic microsphere low-temperature crack-resistant agent, and the functional coating comprises an aqueous resin and hollow UV-resistant particles.

2. The lightweight composite material resistant to ultraviolet aging according to claim 1, characterized in that: The core of the elastic microsphere low-temperature crack-resistant agent is polybutadiene microgel, the outer shell is an organic-inorganic hybrid silicon layer, and a tough intermediate layer is provided between the core and the outer shell. The hollow UV-resistant particles are hollow silica microspheres with ZnO nanocrystals on the surface.

3. The lightweight composite material resistant to ultraviolet aging according to claim 1, characterized in that: The average particle size of the elastic microsphere low-temperature crack-resistant agent is 1.2~2.5μm, and the average particle size of the hollow UV-resistant particles is 0.6~1μm.

4. The method for preparing the UV-resistant lightweight composite material according to claim 1, characterized in that, Includes the following steps: S1. Dry 60-80 parts of polyethylene and 20-40 parts of polycaprolactone, add 10-15 parts of elastic microsphere low-temperature crack-resistant agent and 0.5-2 parts of additives, and mix at high speed until uniform to obtain a premix. S2. The premixed material is melt-blended and extruded in a twin-screw extruder, and then molded by hot press to obtain a composite board; S3. Mix 5-20 parts of hollow UV-resistant granules, 50-70 parts of waterborne polyurethane resin, 0.1-0.5 parts of leveling agent and 30-50 parts of water at high speed with shearing, spray the mixture onto the surface of the composite board, allow it to level, and cure it at 60-80℃ to obtain a lightweight composite material resistant to UV aging.

5. The method for preparing the UV-resistant lightweight composite material according to claim 4, characterized in that, The preparation method of the elastic microsphere low-temperature crack-resistant agent includes the following steps: S11. Butadiene monomer and divinylbenzene in a mass ratio of 95:5 to 85:15 are added to an aqueous solution of sodium dodecyl sulfate, and the mixture is emulsified by high-speed shearing to obtain an emulsion; S12. After heating the emulsion to 65~75℃, potassium persulfate aqueous solution is added in batches and reacted for 6~12h. After the reaction solution is cooled, 50% ethanol aqueous solution is added. The precipitate is centrifuged, washed, and dried at low temperature to obtain low cross-linked polybutadiene microgel. S13. Dissolve POE-g-GMA in an organic solvent, disperse the microgel in the solution, and the mass ratio of POE-g-GMA to microgel is 1:5~1:

2. React at 80~100℃ for 2~6h. After the reaction, cool and pour into ethanol, filter and wash, and vacuum dry to obtain the intermediate product. S14. Disperse the intermediate product, add tetraethyl orthosilicate and silane coupling agent in a mass ratio of 1:0.2~1:1, adjust the pH to 10 with ammonia, hydrolyze and condense, filter and wash, and vacuum dry to obtain the elastic microsphere low-temperature crack-resistant agent.

6. The method for preparing the UV-resistant lightweight composite material according to claim 4, characterized in that, The preparation method of the hollow UV-resistant particles includes the following steps: S21. Add 1-3 wt% PDDA aqueous solution to the polystyrene microsphere dispersion, stir to adsorb, and filter to obtain polystyrene microspheres with positively charged surfaces; S22. Disperse positively charged polystyrene microspheres in ethanol / water at a volume ratio of 4:1, adjust the pH to 10 with ammonia, add tetraethyl orthosilicate as a silicon source precursor, centrifuge and wash after reaction, and calcine at 500~600℃ for 2~4h to obtain hollow silica microspheres. S23. Disperse hollow silica microspheres in water, add zinc acetate dihydrate and urea, wherein the mass ratio of silica, zinc acetate dihydrate and urea is 1:(0.5~2):(1~4), and perform hydrothermal reaction at 90~120℃ for 4~8h. After centrifugation, washing and drying, hollow UV-resistant particles are obtained.

7. The method for preparing the UV-resistant lightweight composite material according to claim 1, characterized in that: The additives in step S1 include antioxidants and lubricants.

8. The method for preparing the UV-resistant lightweight composite material according to claim 1, characterized in that: In step S2, the temperature of each section of the twin-screw extruder is 160~220℃, the screw speed is 100~300r / min, and the compression molding is carried out by hot pressing and holding at 170~190℃ and 5~15MPa for 5~15min, followed by holding the pressure and cooling to 40~60℃ before demolding.

9. The method for preparing the UV-resistant lightweight composite material according to claim 5, characterized in that: In step S13, the organic solvent is toluene or xylene, and the silane coupling agent is KH-550 or KH-570.

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