PMMA composite material based on waste car lamp plastic and preparation method thereof

Abstract

This invention belongs to the field of polymer materials technology, and specifically relates to a PMMA composite material based on waste automotive lamp plastic and its preparation method. The raw materials include the following parts by weight: 70-85 parts waste PMMA granules, 8-18 parts modified magnesium hydroxide, 5-15 parts modified hydroxyapatite, 3-8 parts toughening agent, 0.2-0.8 parts antioxidant, 0.1-0.5 parts ultraviolet absorber, and 0.3-0.8 parts lubricant. The modified magnesium hydroxide is modified through organic processing, phosphorus and nitrogen flame retardancy, and grafting with ultraviolet absorbing groups. The modified hydroxyapatite is modified through phytic acid modification, silane bridging, and grafting with ultraviolet absorbing groups. These two materials work synergistically with waste PMMA granules, toughening agents, and other additives to obtain a PMMA composite material with excellent flame retardancy, outstanding resistance to ultraviolet aging, good mechanical properties, and heat resistance through a specific process, achieving high-value recycling of waste automotive lamp plastic.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a PMMA composite material based on waste automotive lamp plastic and its preparation method. Background Technology

[0002] Polymethyl methacrylate (PMMA) is widely used in automotive headlight covers and other components due to its excellent optical transparency, weather resistance, and mechanical strength. With the continuous growth of the number of cars on the road, the generation of large quantities of waste automotive headlight plastics has led to serious resource and environmental problems. Recycling and reusing waste PMMA is an important way to achieve resource recycling and reduce production costs. However, during long-term use, waste PMMA is prone to molecular chain breakage, molecular weight reduction, and surface aging due to the effects of light, heat, and oxygen, resulting in significant deterioration of its mechanical properties, heat resistance, and weather resistance. If it is simply recycled and used directly like virgin material, the resulting material properties often fail to meet the stringent requirements of high-end applications such as automotive headlights for strength, toughness, flame retardancy, and long-term outdoor color stability.

[0003] Chinese Patent Application No. CN202310068353.4 discloses a PMMA composite material and its preparation method. The PMMA composite material comprises, by mass fraction: 70%-90% PMMA, 5%-10% modified hydroxyapatite, and 5%-15% modified montmorillonite. Hydroxyapatite is added to a titanate coupling agent, and after reaction, a chloroform solution is added to obtain a suspension. The suspension is ultrasonically dispersed for 1-2 hours, and after washing, drying, and grinding, modified hydroxyapatite is obtained. The modified montmorillonite is a quaternary ammonium salt modified montmorillonite. However, both hydroxyapatite and montmorillonite are rigid inorganic particles, and no toughening agent is added. When combined with the brittleness of the PMMA matrix, the elongation at break remains at an extremely low level, failing to meet the structural component's requirement for a rigidity-toughness balance. Chinese Patent Application No. CN201811507029.3 discloses a method for preparing a PMMA composite material. This PMMA composite material is made from components comprising the following weight percentages: 50-83% polymethyl methacrylate and polybutylene terephthalate blend, 5-33% nano-aluminum hydroxide or modified nano-aluminum hydroxide, 0.5-3% antioxidant, and 1-25% toughening agent. The PMMA composite material provided by this invention exhibits excellent heat resistance, aging resistance, and acid and alkali resistance, as well as good mechanical properties and excellent light transmittance, making it suitable for precision optical components in fields such as LEDs. However, PMMA is a non-crystalline polymer, while PBT is a crystalline polymer. The two have different polarity and solubility parameters. Simple blending can lead to phase separation, forming macroscopic or microscopic phase regions. This creates weak points at the two-phase interface, which become stress concentration sources under stress. Consequently, the tensile strength and elongation at break of the material fail to meet expectations, and impact energy is particularly difficult to disperse effectively, thus affecting the notched impact strength. It is evident that none of the aforementioned technologies have resolved the fundamental contradiction between rigidity-toughness balance and compatibility, nor have they addressed the functional regeneration of waste PMMA recycled materials.

[0004] Therefore, there is an urgent need to develop a new high-performance recycled PMMA composite material system that can simultaneously improve its mechanical properties, heat resistance, weather resistance and flame retardancy, so as to expand its application prospects in high-end fields such as automobiles and electronics. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a PMMA composite material based on waste automotive lamp plastic and its preparation method. By using modified magnesium hydroxide and modified hydroxyapatite as synergistic fillers, and combining them with a reasonable ratio of toughening agents, antioxidants, ultraviolet absorbers, and lubricants, waste automotive lamp PMMA particles are efficiently mixed and melt-blended and granulated using a twin-screw extruder before injection molding, resulting in a recycled PMMA composite material with excellent mechanical properties, high flame retardancy, good heat resistance, and outstanding weather resistance.

[0006] The technical solution of the present invention to solve the above problems is as follows: A PMMA composite material based on waste automotive lamp plastic comprises the following raw materials in parts by weight: 70-85 parts waste PMMA granules, 8-18 parts modified magnesium hydroxide, 5-15 parts modified hydroxyapatite, 3-8 parts toughening agent, 0.2-0.8 parts antioxidant, 0.1-0.5 parts ultraviolet absorber, and 0.3-0.8 parts lubricant; The modified magnesium hydroxide is prepared as follows: Step A: Add magnesium hydroxide to deionized water and ultrasonically disperse for 40-50 min. Adjust the pH of the suspension to 7-8, add titanate coupling agent, react at 70-80℃ for 1.5-2 h, cool to room temperature, and obtain organic modified magnesium hydroxide after post-treatment. Step B: When stirring the organically modified magnesium hydroxide, spray an ethanol suspension of ammonium polyphosphate and melamine cyanurate. After stirring for 15-20 minutes, cure at 105-115℃ for 3-3.5 hours to obtain flame-retardant modified magnesium hydroxide. Step C: Add flame-retardant modified magnesium hydroxide to anhydrous ethanol and ultrasonically disperse for 35-40 min. Then add 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone and azobisisobutyronitrile in sequence. React at 60-70℃ under an inert atmosphere for 2-2.5 h. Cool to room temperature and obtain modified magnesium hydroxide after post-treatment.

[0007] Further, the mass ratio of magnesium hydroxide, titanate coupling agent, and deionized water in step A is 10:0.5-0.8:110-130.

[0008] Further, in step B, the mass ratio of the organically modified magnesium hydroxide, ammonium polyphosphate, and melamine cyanurate is 5:8-12:5-8. In the ethanol suspension of ammonium polyphosphate and melamine cyanurate, the solvent is anhydrous ethanol, and the solute is ammonium polyphosphate and melamine cyanurate, wherein the mass ratio of solute to solvent is 1:0.95-1.05.

[0009] Further, in step C, the mass ratio of flame-retardant modified magnesium hydroxide, anhydrous ethanol, 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone, and azobisisobutyronitrile is 10:105-115:0.2-0.6:0.1-0.3.

[0010] Furthermore, the modified hydroxyapatite is prepared as follows: Step a: Disperse hydroxyapatite in deionized water, sonicate for 30-40 min, add phytic acid, adjust pH to 5.3-5.7, react at room temperature for 23-25 ​​h, and obtain phytic acid modified hydroxyapatite after post-treatment; Step b: Disperse phytic acid-modified hydroxyapatite in a mixed solvent, add KH-560, adjust the pH to 4.0-5.0, react at 55-65℃ for 4-5 hours, and obtain silane-bridged hydroxyapatite after post-treatment. Step c: Disperse silane-bridged hydroxyapatite in anhydrous toluene and sonicate for 30-40 min. Add 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and dibutyltin dilaurate. React under an inert atmosphere at 65-75℃ for 3-4 h. After post-treatment, modified hydroxyapatite is obtained.

[0011] Further, the mass ratio of hydroxyapatite, deionized water, and phytic acid in step a is 10:95-105:1.3-1.7.

[0012] Further, the mixed solvent in step b is composed of anhydrous ethanol and deionized water in a volume ratio of 8.5-9.5:1, and the mass ratio of phytic acid-modified hydroxyapatite, KH-560, and the mixed solvent is 10:0.95-1.05:145-155.

[0013] Further, in step c, the mass ratio of silane-bridged hydroxyapatite, anhydrous toluene, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and dibutyltin dilaurate is 10:95-105:0.4-0.8:0.005-0.015.

[0014] Furthermore, the toughening agent is one or more of ethylene-vinyl acetate copolymer, ethylene-acrylate-methyl glycidyl ester terpolymer, and methyl methacrylate; the antioxidant is one or more of antioxidant 300, antioxidant 168, antioxidant 618, and antioxidant 1010; the ultraviolet absorber is one or more of benzotriazole, 2-(2-hydroxy-5-benzyl)benzotriazole, and 2-hydroxy-4-octyloxybenzophenone; and the lubricant is one or more of oleamide, pentaerythritol stearate, and polyethylene wax.

[0015] The above-mentioned method for preparing PMMA composite material based on waste automotive lamp plastic includes the following steps: first, waste PMMA particles, modified magnesium hydroxide, modified hydroxyapatite, toughening agent, antioxidant, ultraviolet absorber and lubricant are mixed evenly, then melt-blended and granulated in a screw extruder, and finally dried and injection molded to obtain PMMA composite material based on waste automotive lamp plastic.

[0016] The present invention has the following beneficial effects: In this invention, modified magnesium hydroxide and modified hydroxyapatite are modified in three steps to form a highly synergistic composite functional network within a PMMA matrix. Modified magnesium hydroxide not only improves interfacial compatibility with a titanate coupling agent but also loads ammonium polyphosphate and melamine cyanurate to construct a flame-retardant system and further grafts 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone to enhance the weather resistance of the PMMA composite. Modified hydroxyapatite introduces phosphate groups and active hydroxyl groups through phytic acid, then strengthens interfacial bonding through silane bridging and covalently anchors 2-(2'-hydroxy-5'-methylphenyl)benzotriazole. Modified magnesium hydroxide and modified hydroxyapatite synergistically exert flame-retardant, UV-resistant, and reinforcing effects within the material: on the one hand, modified magnesium hydroxide's endothermic water release and modified hydroxyapatite promote the formation of a dense carbon layer, significantly increasing the oxygen index; on the other hand, the complementary coverage of two types of UV absorbers with different absorption bands effectively inhibits photo-oxidative degradation, greatly improving the weather resistance of the composite. Modified magnesium hydroxide and modified hydroxyapatite form a complementary functional network in the PMMA matrix, which not only synergistically improves the flame retardancy and weather resistance of the composite material, but also effectively transfers and disperses stress through their uniformly dispersed nanoscale structure and good interfacial bonding with the matrix, thus positively enhancing the tensile strength, impact toughness and heat resistance of the material.

[0017] Waste PMMA particles serve as the matrix, and based on modified magnesium hydroxide and modified hydroxyapatite, they synergistically combine with toughening agents, antioxidants, UV absorbers, and lubricants to achieve a balanced and optimized overall performance. The toughening agent forms a flexible dispersed phase within the matrix, complementing the rigidity of the modified magnesium hydroxide and modified hydroxyapatite. This avoids increased brittleness caused by inorganic fillers and, by absorbing impact energy and preventing crack propagation, synergistically improves elongation at break and notched impact strength, giving the composite material both rigidity and resistance to brittle fracture. The antioxidant, along with the hydrophobic modification layer of the modified magnesium hydroxide and modified hydroxyapatite and the UV absorber, synergistically inhibits thermo-oxidative aging and UV-induced secondary oxidation reactions, reducing the contact between moisture, oxygen, and the matrix, further delaying the aging process and improving the weather resistance of the PMMA composite material. The lubricant, in conjunction with the other components, improves processing fluidity, ensuring smooth melt blending and injection molding processes without compromising the material's mechanical and functional properties. The synergistic effect of each raw material effectively compensates for the performance defects caused by the breakage of the molecular chain of waste PMMA. While realizing the high-value recycling of waste resources, it also optimizes the tensile properties, impact resistance, high temperature resistance, weather resistance and flame retardancy of composite materials in an integrated manner, thus realizing the high-value recycling of waste automotive lamp plastics. Attached Figure Description

[0018] Figure 1 The graph shows the weather resistance test results of PMMA composite materials based on waste automotive lamp plastics prepared in Examples 1-4 and Comparative Examples 1-4 of this invention. Figure 2 The figures show the flame retardant performance test results of PMMA composite materials based on waste automotive lamp plastics prepared in Examples 1-4 and Comparative Examples 1-4 of this invention. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Waste PMMA granules are derived from discarded automotive headlight covers, and after crushing, washing, and drying, the particle size is 2-5mm, and the effective ingredient content is 90%; magnesium hydroxide has an effective ingredient content of 99.9%, a particle size of 30-50nm, and an agglomeration index ≤3. (Shanghai Yingcheng New Materials Co., Ltd.); hydroxyapatite has an effective ingredient content of 99%, a particle size of 200nm, and a density of 3.076. (Temp: 18℃), Hubei Shuaiyan Ligao Biomedical Co., Ltd.; Ammonium polyphosphate, 99% effective ingredient content, particle size 325 mesh, Henan Xinzhiyuan Chemical Products Co., Ltd.; Melamine cyanurate, 99% effective ingredient content, density 1.7. Suzhou Qihang Biotechnology Co., Ltd.; Ethylene-vinyl acetate copolymer relative density 0.92-0.98 Average molecular weight 2000, Dongguan Kaiyuan Plastic Raw Materials Co., Ltd.; DuPont, manufacturer of ethylene-acrylate-methylglycidyl terpolymer, Dongguan Shenghao Plastic Raw Materials Co., Ltd.; Polyethylene wax particle size 1000 mesh, density 0.99 Guangzhou Xinxi Metallurgical Chemical Co., Ltd.; Phytic acid is a colorless or slightly yellow viscous liquid with a phytic acid content of 50.1%, Shanghai Quanyan Biotechnology Co., Ltd.

[0021] Example 1 A PMMA composite material based on waste automotive lamp plastic comprises the following raw materials in parts by weight: 70 parts waste PMMA granules, 8 parts modified magnesium hydroxide, 5 parts modified hydroxyapatite, 3 parts toughening agent, 0.2 parts antioxidant, 0.1 parts ultraviolet absorber, and 0.3 parts lubricant. The modified magnesium hydroxide is prepared as follows: Step A: Add magnesium hydroxide to deionized water and ultrasonically disperse for 45 min at a power of 300 W and a frequency of 40 kHz. Adjust the pH of the suspension to 7-8 with 0.1 M sodium hydroxide solution. Add titanate coupling agent and stir at 75 °C for 1.8 h. After naturally cooling to room temperature, centrifuge at 8000 r / min for 15 min. Wash the precipitate three times with deionized water and vacuum dry at 75 °C for 5 h to obtain organically modified magnesium hydroxide. The mass ratio of magnesium hydroxide, titanate coupling agent and deionized water is 10:0.6:120. Step B: Organically modified magnesium hydroxide is sprayed with an ethanol suspension of ammonium polyphosphate and melamine cyanurate while stirring at a high speed of 1200 rpm. After stirring at high speed for 17 min, it is cured at 110℃ for 3.2 h to obtain flame-retardant modified magnesium hydroxide. The mass ratio of organically modified magnesium hydroxide, ammonium polyphosphate, and melamine cyanurate is 5:10:6. The solvent in the ethanol suspension of ammonium polyphosphate and melamine cyanurate is anhydrous ethanol, and the solutes are ammonium polyphosphate and melamine cyanurate, with a mass ratio of solute to solvent of 1:1. Step C: Add flame-retardant modified magnesium hydroxide to anhydrous ethanol and ultrasonically disperse for 38 min at a power of 300 W and a frequency of 40 kHz. Then add 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone and azobisisobutyronitrile in sequence. React at 65 °C under nitrogen atmosphere for 2.3 h. After naturally cooling to room temperature, filter. Wash the filter cake twice with anhydrous ethanol, vacuum dry at 70 °C for 4 h, and pulverize to 300 nm to obtain modified magnesium hydroxide. The mass ratio of flame-retardant modified magnesium hydroxide, anhydrous ethanol, 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone and azobisisobutyronitrile is 10:110:0.4:0.2.

[0022] The modified hydroxyapatite is prepared as follows: Step a: Disperse hydroxyapatite in deionized water and ultrasonically disperse for 35 min at a power of 300 W and a frequency of 40 kHz. Add phytic acid and adjust the pH to 5.3-5.7 with 8% dilute ammonia. Stir at 800 rpm for 24 h at room temperature. After the reaction is completed, centrifuge at 8000 r / min for 15 min and freeze-dry for 24 h to obtain phytic acid modified hydroxyapatite. The mass ratio of hydroxyapatite, deionized water and phytic acid is 10:100:1.5. Step b: Disperse phytic acid-modified hydroxyapatite in a mixed solvent, add KH-560, adjust the pH to 4.0-5.0 with 1M acetic acid solution, stir and react at 60℃ for 4.5h. After the reaction is complete, centrifuge at 8000r / min for 15min, wash 3 times with anhydrous ethanol, and vacuum dry at 80℃ for 6h to obtain silane-bridged hydroxyapatite. The mixed solvent consists of anhydrous ethanol and deionized water in a volume ratio of 9:1, and the mass ratio of phytic acid-modified hydroxyapatite, KH-560 and mixed solvent is 10:1:150. Step c: Disperse silane-bridged hydroxyapatite in anhydrous toluene and ultrasonically disperse for 35 min at 300 W and 40 kHz. Add 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and dibutyltin dilaurate and react at 70 °C for 3.5 h under nitrogen atmosphere. After the reaction is complete, centrifuge at 8000 r / min for 15 min, wash twice with toluene, vacuum dry at 70 °C for 12 h, and pulverize to 500 nm to obtain modified hydroxyapatite. The mass ratio of silane-bridged hydroxyapatite, anhydrous toluene, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and dibutyltin dilaurate is 10:100:0.6:0.01.

[0023] The toughening agent is ethylene-vinyl acetate copolymer; the antioxidant is antioxidant 300; the ultraviolet absorber is benzotriazole; and the lubricant is oleamide.

[0024] The above-mentioned method for preparing PMMA composite materials based on waste automotive lamp plastics includes the following steps: First, waste PMMA particles, modified magnesium hydroxide, and modified hydroxyapatite are mixed at 200 rpm for 3 minutes; then, toughening agent, antioxidant, UV absorber, and lubricant are added and mixed at 800 rpm for 10 minutes; then, the mixture is melt-blended and granulated in a twin-screw extruder, wherein the screw speed during melt blending is 300 rpm, the screw diameter is 40 mm, the length-to-diameter ratio (L / D) is ≥40:1, and the screw temperature is set as follows: Zone 1 175-180℃, Zone 2 190-195℃, Zone 3 200- The temperature ranges from 205℃ in zone four to 205-210℃ in zone five, and from 200-205℃ in zone five. The die head temperature is 195-200℃. During granulation, the extruded strip is cooled in a water bath at 25-30℃ and then cut into uniform cylindrical pellets of 3-4mm in length by a pelletizer. Finally, the pellets are dried at 85℃ for 4 hours and then injection molded using a standard plastic injection molding machine. The barrel temperature from back to front is 195℃, 200℃, and 205℃, the die temperature is 60-70℃, the injection pressure is 70-80MPa, the holding pressure is 50-60MPa, and the cooling time is 30s. This yields a PMMA composite material based on waste automotive headlight plastic.

[0025] Example 2 A PMMA composite material based on waste automotive lamp plastic comprises the following raw materials in parts by weight: 85 parts waste PMMA granules, 18 parts modified magnesium hydroxide, 15 parts modified hydroxyapatite, 8 parts toughening agent, 0.8 parts antioxidant, 0.5 parts ultraviolet absorber, and 0.8 parts lubricant. The preparation methods for the modified magnesium hydroxide and the modified hydroxyapatite are the same as in Example 1.

[0026] The toughening agent is an ethylene-acrylate-methyl glycidyl ester terpolymer; the antioxidant is antioxidant 168; the ultraviolet absorber is benzotriazole; and the lubricant is pentaerythritol stearate.

[0027] The preparation method of the PMMA composite material based on waste automotive lamp plastic described above is the same as in Example 1.

[0028] Example 3 A PMMA composite material based on waste automotive lamp plastic comprises the following raw materials in parts by weight: 80 parts waste PMMA granules, 13 parts modified magnesium hydroxide, 10 parts modified hydroxyapatite, 5 parts toughening agent, 0.5 parts antioxidant, 0.3 parts ultraviolet absorber, and 0.6 parts lubricant. The preparation methods for the modified magnesium hydroxide and the modified hydroxyapatite are the same as in Example 1.

[0029] The toughening agent is methyl methacrylate; the antioxidant is antioxidant 1010; the ultraviolet absorber is 2-(2-hydroxy-5-benzyl)benzotriazole; and the lubricant is polyethylene wax.

[0030] The preparation method of the PMMA composite material based on waste automotive lamp plastic described above is the same as in Example 1.

[0031] Example 4 A PMMA composite material based on waste automotive lamp plastic comprises the following raw materials in parts by weight: 80 parts waste PMMA granules, 13 parts modified magnesium hydroxide, 10 parts modified hydroxyapatite, 5 parts toughening agent, 0.5 parts antioxidant, 0.3 parts ultraviolet absorber, and 0.6 parts lubricant. The modified magnesium hydroxide is prepared as follows: Step A: Add magnesium hydroxide to deionized water and ultrasonically disperse for 50 min at 300 W and 40 kHz. Adjust the pH of the suspension to 7-8 with 0.1 M sodium hydroxide solution. Add titanate coupling agent and stir at 80 °C for 2 h. After naturally cooling to room temperature, centrifuge at 8000 r / min for 15 min. Wash the precipitate three times with deionized water and vacuum dry at 75 °C for 5 h to obtain organically modified magnesium hydroxide. The mass ratio of magnesium hydroxide, titanate coupling agent and deionized water is 10:0.8:130. Step B: Organically modified magnesium hydroxide is sprayed with an ethanol suspension of ammonium polyphosphate and melamine cyanurate while stirring at a high speed of 1200 rpm. After continuing to stir at high speed for 20 min, it is cured at 115℃ for 3.5 h to obtain flame-retardant modified magnesium hydroxide. The mass ratio of organically modified magnesium hydroxide, ammonium polyphosphate, and melamine cyanurate is 5:12:8. The solvent in the ethanol suspension of ammonium polyphosphate and melamine cyanurate is anhydrous ethanol, and the solutes are ammonium polyphosphate and melamine cyanurate, with a mass ratio of solute to solvent of 1:1.05. Step C: Add flame-retardant modified magnesium hydroxide to anhydrous ethanol and ultrasonically disperse for 40 min at a power of 300 W and a frequency of 40 kHz. Then add 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone and azobisisobutyronitrile in sequence. React at 70 °C for 2.5 h under a nitrogen atmosphere. After naturally cooling to room temperature, filter the mixture. Wash the filter cake twice with anhydrous ethanol and vacuum dry at 70 °C for 4 h. Crush the mixture to 300 nm to obtain modified magnesium hydroxide. The mass ratio of flame-retardant modified magnesium hydroxide, anhydrous ethanol, 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone, and azobisisobutyronitrile is 10:115:0.6:0.3.

[0032] The modified hydroxyapatite is prepared as follows: Step a: Disperse hydroxyapatite in deionized water and ultrasonically disperse it for 40 min at a power of 300 W and a frequency of 40 kHz. Add phytic acid and adjust the pH to 5.3-5.7 with 8% dilute ammonia. Stir at 800 rpm for 25 h at room temperature. After the reaction is completed, centrifuge at 8000 r / min for 15 min and freeze dry for 24 h to obtain phytic acid modified hydroxyapatite. The mass ratio of hydroxyapatite, deionized water and phytic acid is 10:105:1.7. Step b: Disperse phytic acid-modified hydroxyapatite in a mixed solvent, add KH-560, adjust the pH to 4.0-5.0 with 1M acetic acid solution, stir and react at 65℃ for 5h, after the reaction is complete, centrifuge at 8000r / min for 15min, wash 3 times with anhydrous ethanol, and vacuum dry at 80℃ for 6h to obtain silane-bridged hydroxyapatite. The mixed solvent consists of anhydrous ethanol and deionized water in a volume ratio of 9.5:1, and the mass ratio of phytic acid-modified hydroxyapatite, KH-560 and mixed solvent is 10:1.05:155. Step c: Disperse silane-bridged hydroxyapatite in anhydrous toluene and ultrasonically disperse for 40 min at 300 W and 40 kHz. Add 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and dibutyltin dilaurate. React at 75 °C under nitrogen atmosphere for 4 h. After the reaction is complete, centrifuge at 8000 r / min for 15 min, wash twice with toluene, vacuum dry at 70 °C for 12 h, and pulverize to 500 nm to obtain modified hydroxyapatite. The mass ratio of silane-bridged hydroxyapatite, anhydrous toluene, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and dibutyltin dilaurate is 10:105:0.8:0.015.

[0033] The toughening agent is methyl methacrylate; the antioxidant is antioxidant 1010; the ultraviolet absorber is 2-hydroxy-4-octyloxybenzophenone; and the lubricant is polyethylene wax.

[0034] The preparation method of the PMMA composite material based on waste automotive lamp plastic described above is the same as in Example 1.

[0035] Comparative Example 1 A PMMA composite material based on waste automotive lamp plastic comprises the following raw materials in parts by weight: 50 parts waste PMMA granules, 5 parts modified magnesium hydroxide, 3 parts modified hydroxyapatite, 1 part toughening agent, 0.5 parts antioxidant, 0.3 parts ultraviolet absorber, and 0.6 parts lubricant. The modified magnesium hydroxide is prepared as follows: Step A: Add magnesium hydroxide to deionized water and ultrasonically disperse it for 50 min at a power of 300 W and a frequency of 40 kHz. Add titanate coupling agent and stir the reaction at 80 °C for 2 h. After naturally cooling to room temperature, centrifuge at 8000 r / min for 15 min. Wash the precipitate three times with deionized water and vacuum dry it at 75 °C for 5 h to obtain organic modified magnesium hydroxide. The mass ratio of magnesium hydroxide, titanate coupling agent and deionized water is 10:0.1:130. Step B: Organically modified magnesium hydroxide is sprayed with an ethanol suspension of ammonium polyphosphate and melamine cyanurate while stirring at 300 rpm. After stirring for 20 min, it is cured at 115℃ for 3.5 h to obtain flame-retardant modified magnesium hydroxide. The mass ratio of organically modified magnesium hydroxide, ammonium polyphosphate, and melamine cyanurate is 5:5:8. The solvent in the ethanol suspension of ammonium polyphosphate and melamine cyanurate is anhydrous ethanol, and the solutes are ammonium polyphosphate and melamine cyanurate, with a mass ratio of solute to solvent of 1:0.5. Step C: Add flame-retardant modified magnesium hydroxide to anhydrous ethanol and ultrasonically disperse for 40 min at a power of 300 W and a frequency of 40 kHz. Then add 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone and azobisisobutyronitrile in sequence. React at 70 °C for 2.5 h. After naturally cooling to room temperature, filter. Wash the filter cake twice with anhydrous ethanol and vacuum dry at 70 °C for 4 h. Pulverize to 300 nm to obtain modified magnesium hydroxide. The mass ratio of flame-retardant modified magnesium hydroxide, anhydrous ethanol, 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone and azobisisobutyronitrile is 10:115:0.1:0.3.

[0036] The modified hydroxyapatite is prepared as follows: Step a: Disperse hydroxyapatite in deionized water and ultrasonically disperse it for 40 min at a power of 300 W and a frequency of 40 kHz. Add phytic acid and stir at 800 rpm for 25 h at room temperature. After the reaction is completed, centrifuge at 8000 r / min for 15 min and freeze dry for 24 h to obtain phytic acid modified hydroxyapatite. The mass ratio of hydroxyapatite, deionized water and phytic acid is 10:105:1. Step b: Disperse phytic acid-modified hydroxyapatite in a mixed solvent, add KH-560, adjust the pH to 4.0-5.0 with 1M acetic acid solution, stir and react at room temperature for 5 hours. After the reaction is complete, centrifuge at 8000 r / min for 15 min, wash three times with anhydrous ethanol, and vacuum dry at 80℃ for 6 hours to obtain silane-bridged hydroxyapatite. The mixed solvent consists of anhydrous ethanol and deionized water in a volume ratio of 9.5:1, and the mass ratio of phytic acid-modified hydroxyapatite, KH-560, and mixed solvent is 10:0.5:155. Step c: Disperse silane-bridged hydroxyapatite in anhydrous toluene and ultrasonically disperse for 40 min at 300 W and 40 kHz. Add 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and dibutyltin dilaurate and react at room temperature for 4 h. After the reaction is complete, centrifuge at 8000 r / min for 15 min, wash twice with toluene, vacuum dry at 70 °C for 12 h, and pulverize to 500 nm to obtain modified hydroxyapatite. The mass ratio of silane-bridged hydroxyapatite, anhydrous toluene, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and dibutyltin dilaurate is 10:105:0.1:0.001.

[0037] The toughening agent is methyl methacrylate; the antioxidant is antioxidant 1010; the ultraviolet absorber is 2-hydroxy-4-octyloxybenzophenone; and the lubricant is polyethylene wax.

[0038] The preparation method of the PMMA composite material based on waste automotive lamp plastic described above is the same as in Example 1.

[0039] Comparative Example 2 A PMMA composite material based on waste automotive lamp plastic, wherein commercially available magnesium hydroxide is used instead of modified magnesium hydroxide, and all other aspects are the same as in Example 1.

[0040] Comparative Example 3 A PMMA composite material based on waste automotive lamp plastic, wherein commercially available hydroxyapatite is used instead of modified hydroxyapatite, and all other aspects are the same as in Example 1.

[0041] Comparative Example 4 A PMMA composite material based on waste automotive lamp plastic is provided, wherein commercially available magnesium hydroxide is used instead of modified magnesium hydroxide, and commercially available hydroxyapatite is used instead of modified hydroxyapatite, and the rest are the same as in Example 1.

[0042] First, the PMMA composite materials based on waste automotive lamp plastics from Examples 1-4 and Comparative Examples 1-4 were injection molded and then cut into strips of the dimensions required by the following test methods. The following performance tests were then conducted, and the test results are shown in Table 1. Figure 1-2 As shown.

[0043] Tensile property test: The tensile strength and elongation at break of the specimen were tested according to the requirements of ISO 527-2 2025. The specimen size was 135×10×4mm and the tensile speed was 50mm / min.

[0044] Impact resistance test: The notched impact strength of the specimen in a simply supported beam was tested according to the requirements of ISO 179-1 2023. The specimen size was 80×10×4mm, with a type A notch.

[0045] Heat resistance test: The Vicat softening temperature of the test specimens was tested according to the requirements of GB / T 1633-2000 "Determination of Vicat softening temperature (VST) of flexible plastics".

[0046] Weather resistance test: According to GB / T 16422.3-2022 "Laboratory Light Source Exposure Test Method for Plastics Part 3: Fluorescent Ultraviolet Lamps", 6.6 Exposure Condition A Method 2 cycles, after 10 exposure cycles, compare the color of the sample before and after the exposure cycle to obtain the total color difference value △E. The larger the value of △E, the greater the color change and the worse the weather resistance of the product.

[0047] Flame retardant performance test: The oxygen index value of the specimen was tested according to the requirements of GB / T 2406.2-2009 "Determination of burning behavior of plastics by oxygen index method - Part 2: Room temperature test".

[0048] Table 1 Performance Test Results From Table 1 and Figure 1-2It can be seen that the PMMA composite materials based on waste automotive lamp plastics prepared in Examples 1-4 have better overall performance than the composite materials prepared in Comparative Examples 1-4. They have better tensile strength and elongation at break, significantly improved notched impact strength, higher Vicat softening temperature, better weather resistance, and further improved oxygen index. They have achieved synergistic optimization of mechanical, heat resistance, weather resistance and flame retardant properties. Therefore, it can be shown that the raw material ratios and preparation process parameters proposed in this invention are optimal.

[0049] From Table 1 and Figure 1-2 As can be seen, compared with Examples 1-4, the PMMA composite material based on waste automotive lamp plastic prepared in Comparative Example 2 showed a decrease in tensile properties, impact resistance, heat resistance, weather resistance, and flame retardancy. This is because magnesium hydroxide replaced modified magnesium hydroxide. In step A of the example, magnesium hydroxide was organically modified by titanate coupling agent. Its main function is to significantly improve the dispersibility and compatibility of magnesium hydroxide in the PMMA matrix by introducing hydrophobic organic groups. This modification step has a positive impact on the tensile properties and impact resistance of the composite material because better dispersibility reduces interface defects and enhances stress transfer efficiency, thereby helping to improve tensile strength and elongation at break. At the same time, it reduces the brittleness caused by particle agglomeration and improves notched impact strength. In addition, the surface energy of the organically modified magnesium hydroxide is reduced, which reduces the flow resistance during processing and indirectly supports the stability of high-temperature resistance. In step B of the embodiment, an ammonium polyphosphate (APP) and melamine cyanurate (MCA) flame-retardant system is coated onto the surface of organically modified magnesium hydroxide, constructing a highly efficient, multi-layered synergistic flame-retardant protective layer. This protective layer significantly improves the flame-retardant safety and heat resistance of the composite material. When heated or burning, the internal magnesium hydroxide decomposes, absorbs heat, and releases water vapor, diluting combustible gases and oxygen. Simultaneously, the outer APP and MCA react rapidly, catalyzing the matrix to form char and releasing inert gases, creating an expanded, dense, and robust char layer. This char layer effectively isolates heat and oxygen transfer, thus synergistically exerting a strong flame-retardant effect and significantly improving the oxygen index of the material. Furthermore, this coating layer further restricts the thermal movement of polymer segments, increasing the heat distortion temperature of the composite material. In step C of the embodiment, ultraviolet-absorbing functional groups are covalently bonded to the surface of the flame-retardant-coated magnesium hydroxide through a free radical grafting reaction, providing the composite material with durable, stable, and non-migrating internal ultraviolet protection. The grafted UV-absorbing molecules can effectively absorb and convert high-energy UV light, preventing direct UV attack on the PMMA molecular chain and thus preventing photo-oxidative degradation, thereby greatly improving the material's weather resistance. Simultaneously, because the UV-absorbing groups are fixed by covalent bonds, the drawbacks of small-molecule additives such as easy migration and precipitation are avoided, resulting in more durable UV protection.

[0050] From Table 1 and Figure 1-2It can be seen that, compared with Examples 1-4, the PMMA composite material based on waste automotive lamp plastic prepared in Comparative Example 3 showed a decrease in tensile properties, impact resistance, heat resistance, weather resistance, and flame retardancy. This is because hydroxyapatite replaced modified hydroxyapatite. In step a of the example, phosphate groups and active hydroxyl groups were introduced into the surface of inorganic particles through anchoring modification with phytic acid, which constructed an additional phosphorus-based flame retardant source for the material and simultaneously created reaction sites for subsequent chemical grafting. Phytic acid molecules rely on their multiple phosphate groups to form strong coordination bonds with calcium ions on the surface of the hydroxyapatite lattice, which not only fixes the phosphorus element on the particle surface in the form of stable chemical bonds, but also carries a large number of hydroxyl groups to provide an active endpoint for condensation reaction of silane coupling agents. This structural reshaping has a dual optimization effect on the flame retardant properties and interfacial bonding ability of PMMA composite materials. The introduction of phosphorus can form a synergistic effect with the phosphorus-nitrogen flame retardant system of modified magnesium hydroxide during combustion, promoting the formation of a denser expanded char layer. In step b of this embodiment, KH-560 silane coupling agent is used to bridge phytic acid-modified hydroxyapatite, constructing a phosphorus-nitrogen-silicon ternary synergistic flame-retardant system and solving the problem of poor compatibility between the inorganic phase of hydroxyapatite and the organic phase of PMMA. The silanol groups generated by the hydrolysis of the silane coupling agent in an acidic ethanol-water system undergo a condensation reaction with the phytic acid hydroxy groups introduced in the first step, grafting nitrogen- and silicon-containing organic segments onto the particle surface in a covalent bond form. This structural transformation significantly optimizes the mechanical strength, heat resistance, and impact toughness of the PMMA composite material. The introduction of silicon can be converted into a silica ceramic framework at high temperatures to enhance the structural stability of the carbon layer, while nitrogen provides the gas-phase flame-retardant active ingredient, and the flexible structure of the silane segments effectively alleviates interfacial stress concentration. In step c of this embodiment, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole is introduced as an ultraviolet absorber onto the silane-bridged hydroxyapatite surface, endowing the material with excellent weather resistance. The UV absorber is firmly fixed to the filler surface by covalent bonds, making it difficult to migrate or precipitate. This design also effectively blocks UVA radiation, preventing the polymer backbone from degrading due to UV irradiation and significantly reducing the color difference value after aging. In addition, the presence of the UV absorber inhibits the oxidation reaction inside the material, further delaying the aging process and maintaining the overall performance of the material. Meanwhile, hydroxyapatite itself has high thermal stability, and the moisture and other gases released during combustion also help improve the flame retardant properties of the material.

[0051] From Table 1 and Figure 1-2It can be seen that, compared with Examples 1-4, the PMMA composite material based on waste automotive lamp plastic prepared in Comparative Example 4 performed the worst in terms of tensile properties, impact resistance, heat resistance, weather resistance, and flame retardancy. This is because magnesium hydroxide replaced modified magnesium hydroxide, and hydroxyapatite replaced modified hydroxyapatite. Modified magnesium hydroxide mainly serves as a flame retardant and UV shielding skeleton. After surface grafting with APP and MCA, it can form an expanding flame retardant layer during combustion, effectively insulating heat and oxygen. At the same time, the UV-absorbing groups grafted on the surface provide resistance to UV aging. Modified hydroxyapatite serves as an interface bridge and functional enhancer. Its surface phytic acid and silane layers significantly improve compatibility with the PMMA matrix, reduce interface defects, and also improve the thermal stability and weather resistance of the material. The core of their synergistic effect lies in constructing a multi-dimensional reinforcing network. In terms of flame retardancy, the endothermic decomposition of magnesium hydroxide combined with the dense carbon layer formed by hydroxyapatite produces a gas-phase-condensed-phase synergistic flame retardant effect, significantly improving flame retardant performance. In terms of mechanical properties, both are uniformly dispersed in the matrix, working together to enhance and toughen the material, which helps to improve tensile strength and impact toughness. In terms of durability, the different ultraviolet absorbing groups grafted onto the surfaces of both materials can synergistically shield ultraviolet rays, delay the photoaging of the material, reduce color difference changes, and jointly support the thermal stability of the material.

[0052] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PMMA composite material based on waste automotive lamp plastic, characterized in that, The raw materials include the following parts by weight: 70-85 parts waste PMMA granules, 8-18 parts modified magnesium hydroxide, 5-15 parts modified hydroxyapatite, 3-8 parts toughening agent, 0.2-0.8 parts antioxidant, 0.1-0.5 parts ultraviolet absorber, and 0.3-0.8 parts lubricant; The modified magnesium hydroxide is prepared as follows: Step A: Add magnesium hydroxide to deionized water and ultrasonically disperse for 40-50 min. Adjust the pH of the suspension to 7-8, add titanate coupling agent, react at 70-80℃ for 1.5-2 h, cool to room temperature, and obtain organic modified magnesium hydroxide after post-treatment. Step B: When stirring the organically modified magnesium hydroxide, spray an ethanol suspension of ammonium polyphosphate and melamine cyanurate. After stirring for 15-20 minutes, cure at 105-115℃ for 3-3.5 hours to obtain flame-retardant modified magnesium hydroxide. Step C: Add flame-retardant modified magnesium hydroxide to anhydrous ethanol and ultrasonically disperse for 35-40 min. Then add 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone and azobisisobutyronitrile in sequence. React at 60-70℃ under an inert atmosphere for 2-2.5 h. Cool to room temperature and obtain modified magnesium hydroxide after post-treatment.

2. The PMMA composite material based on waste automotive lamp plastic according to claim 1, characterized in that, The mass ratio of magnesium hydroxide, titanate coupling agent, and deionized water in step A is 10:0.5-0.8:110-130.

3. The PMMA composite material based on waste automotive lamp plastic according to claim 1, characterized in that, In step B, the mass ratio of the organically modified magnesium hydroxide, ammonium polyphosphate, and melamine cyanurate is 5:8-12:5-8. The solvent in the ethanol suspension of ammonium polyphosphate and melamine cyanurate is anhydrous ethanol, and the solutes are ammonium polyphosphate and melamine cyanurate, wherein the mass ratio of solute to solvent is 1:0.95-1.

05.

4. The PMMA composite material based on waste automotive lamp plastic according to claim 1, characterized in that, The mass ratio of the flame-retardant modified magnesium hydroxide, anhydrous ethanol, 2-hydroxy-4-(2-acryloyloxyethoxy)benzophenone, and azobisisobutyronitrile in step C is 10:105-115:0.2-0.6:0.1-0.

3.

5. The PMMA composite material based on waste automotive lamp plastic according to claim 1, characterized in that, The modified hydroxyapatite is prepared as follows: Step a: Disperse hydroxyapatite in deionized water, sonicate for 30-40 min, add phytic acid, adjust pH to 5.3-5.7, react at room temperature for 23-25 ​​h, and obtain phytic acid modified hydroxyapatite after post-treatment; Step b: Disperse phytic acid-modified hydroxyapatite in a mixed solvent, add KH-560, adjust the pH to 4.0-5.0, react at 55-65℃ for 4-5 hours, and obtain silane-bridged hydroxyapatite after post-treatment. Step c: Disperse silane-bridged hydroxyapatite in anhydrous toluene and sonicate for 30-40 min. Add 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and dibutyltin dilaurate. React under an inert atmosphere at 65-75℃ for 3-4 h. After post-treatment, modified hydroxyapatite is obtained.

6. The PMMA composite material based on waste automotive lamp plastic according to claim 5, characterized in that, The mass ratio of hydroxyapatite, deionized water, and phytic acid in step a is 10:95-105:1.3-1.

7.

7. The PMMA composite material based on waste automotive lamp plastic according to claim 5, characterized in that, The mixed solvent in step b consists of anhydrous ethanol and deionized water in a volume ratio of 8.5-9.5:1, and the mass ratio of phytic acid-modified hydroxyapatite, KH-560, and the mixed solvent is 10:0.95-1.05:145-155.

8. The PMMA composite material based on waste automotive lamp plastic according to claim 5, characterized in that, In step c, the mass ratio of silane-bridged hydroxyapatite, anhydrous toluene, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and dibutyltin dilaurate is 10:95-105:0.4-0.8:0.005-0.

015.

9. The PMMA composite material based on waste automotive lamp plastic according to claim 1, characterized in that, The toughening agent is one or more of ethylene-vinyl acetate copolymer, ethylene-acrylate-methyl glycidyl ester terpolymer, and methyl methacrylate; the antioxidant is one or more of antioxidant 300, antioxidant 168, antioxidant 618, and antioxidant 1010; the ultraviolet absorber is one or more of benzotriazole, 2-(2-hydroxy-5-benzyl)benzotriazole, and 2-hydroxy-4-octyloxybenzophenone; and the lubricant is one or more of oleamide, pentaerythritol stearate, and polyethylene wax.

10. The method for preparing PMMA composite material based on waste automotive lamp plastic as described in any one of claims 1-9, characterized in that, Includes the following steps: First, waste PMMA granules, modified magnesium hydroxide, modified hydroxyapatite, toughening agent, antioxidant, ultraviolet absorber and lubricant are mixed evenly. Then, they are melt-blended and granulated in a screw extruder. Finally, they are dried and injection molded to obtain PMMA composite material based on waste automotive lamp plastic.

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