High-wear-resistance flame-retardant thermoplastic elastomer and preparation method thereof

Abstract

The invention discloses a high-wear-resistance flame-retardant thermoplastic elastomer and a preparation method thereof, and relates to the technical field of thermoplastic elastomers. The flame-retardant ethylene-octylene copolymer composite material is prepared from the following raw materials in parts by mass: 100 to 120 parts of ethylene-octylene copolymer, 8 to 10 parts of composite flame retardant, 2 to 3 parts of modified boron nitride nanotube, 4 to 5 parts of polytetrafluoroethylene micro powder, 0.5 to 0.6 part of antioxidant 1010 and 0.5 to 0.6 part of light stabilizer 770. The modified boron nitride nanotube is prepared by firstly carrying out graft modification on a boron nitride nanotube through 3-glycidyl ether oxypropyl methyl diethoxy silane and then carrying out graft modification on the boron nitride nanotube through 4-formyl phenylboronic acid pinacol ester. Due to the introduction of the composite flame retardant, the modified boron nitride nanotube, the polytetrafluoroethylene micro powder and the like, the wear resistance, the flame retardance and the aging resistance of the polyolefin thermoplastic elastomer are effectively improved. Therefore, the method has a wider application prospect.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic elastomer technology, specifically to a highly wear-resistant and flame-retardant thermoplastic elastomer and its preparation method. Background Technology

[0002] Thermoplastic elastomers are a class of polymeric materials that combine the elasticity of rubber with the processability of plastics. They can be repeatedly processed and molded without vulcanization, and offer advantages such as environmental friendliness, high efficiency, and low cost. They are widely used in many fields, including automotive parts, appliance housings, medical devices, and packaging materials. Among them, polyolefin thermoplastic elastomers possess excellent weather resistance and chemical stability, and are widely used in areas such as automotive bumpers and sealing strips.

[0003] However, polyolefin thermoplastic elastomers still have the following performance shortcomings in practical applications: First, their wear resistance is poor, with a relatively high coefficient of friction, making them prone to scratches and wear under dynamic friction or heavy-duty wear conditions. Second, their flame retardancy is weak; polyolefins themselves are flammable materials, easily igniting and releasing molten droplets upon contact with fire, and even simple flame-retardant modification can easily lead to a decline in mechanical properties. Third, their resistance to environmental aging is limited; long-term exposure to high temperature and humid environments can easily damage the compatibility between hard and soft segments, leading to problems such as cracking, discoloration, and elasticity loss. Therefore, the wear resistance, flame retardancy, and aging resistance of existing polyolefin thermoplastic elastomers still need to be improved. Summary of the Invention

[0004] The purpose of this invention is to provide a highly wear-resistant and flame-retardant thermoplastic elastomer and its preparation method, thereby solving the following technical problems: Existing polyolefin thermoplastic elastomers still suffer from poor wear resistance, flame retardancy, and aging resistance.

[0005] The objective of this invention can be achieved through the following technical solutions: A highly wear-resistant and flame-retardant thermoplastic elastomer comprises the following raw materials in parts by weight: 100-120 parts of ethylene-octene copolymer, 8-10 parts of composite flame retardant, 2-3 parts of modified boron nitride nanotubes, 4-5 parts of polytetrafluoroethylene micro powder, 0.5-0.6 parts of antioxidant 1010, and 0.5-0.6 parts of light stabilizer 770; The composite flame retardant is prepared from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, triethylamine, butyl acrylate, n-hexane, dithiodiglycolic acid, 4-dimethylaminopyridine, and N,N'-dicyclohexylcarbodiimide. The modified boron nitride nanotubes are prepared by first grafting boron nitride nanotubes with 3-glycidyl etheroxypropylmethyldiethoxysilane, and then grafting them with 4-formylphenylboronic acid pinacol ester.

[0006] Preferably, the preparation method of the composite flame retardant is as follows: A1: Add butyl acrylate to anhydrous tetrahydrofuran and stir for 10-15 min to obtain a butyl acrylate solution; A2: Add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triethylamine to anhydrous tetrahydrofuran and stir under a nitrogen atmosphere for 30-40 min. Then, add butyl acrylate solution dropwise at 0-5℃ and stir for 50-60 min. Then, reflux at 66-68℃ for 10-12 h. Remove 80%-85% of tetrahydrofuran by vacuum distillation. Then, add n-hexane and ultrasonically disperse for 20-30 min. Finally, let it stand at -20℃ for 20-24 h to crystallize. Filter and wash the filter cake with cold n-hexane at -20℃ and dry to obtain phosphorus-containing flame retardant. A3: Dithiodiglycolic acid, 4-dimethylaminopyridine, and anhydrous toluene are added to a phosphorus-containing flame retardant and stirred under a nitrogen atmosphere for 30-50 min. Then, N,N'-dicyclohexylcarbodiimide is added and reacted at 0-5℃ for 2.5-3 h. After filtering to remove the precipitate, the reaction is carried out at 20-25℃ for 12-16 h. Then, the temperature is raised to 80-90℃ and filtered. After cooling the filtrate, it is washed and the pH is adjusted to 6.5-7.0. Then, it is allowed to stand for 30-50 min and separated. Finally, the organic phase is dried with anhydrous magnesium sulfate, filtered, and toluene is removed by rotary evaporation under reduced pressure to obtain the composite flame retardant.

[0007] Preferably, the ratio of anhydrous tetrahydrofuran to butyl acrylate in A1 is 100-110 mL: 13.8 g.

[0008] Preferably, the ratio of anhydrous tetrahydrofuran, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, triethylamine, butyl acrylate solution, and n-hexane in A2 is 150 mL: 29.6 g: 0.5 g: 100-110 mL: 200 mL.

[0009] Preferably, the ratio of phosphorus-containing flame retardant, dithiodiglycolic acid, 4-dimethylaminopyridine, anhydrous toluene, and N,N'-dicyclohexylcarbodiimide in A3 is 34.2g:15.3g:0.5g:250-270mL:19.6g.

[0010] Preferably, the modified boron nitride nanotubes are prepared as follows: B1: Add boron nitride nanotubes to anhydrous toluene and sonicate for 2-3 hours. Then, under a nitrogen atmosphere, add 3-glycidyl etheroxypropylmethyldiethoxysilane, deionized water, and glacial acetic acid and reflux at 110°C for 16-18 hours. After cooling, centrifuge, wash the precipitate, and dry to obtain aminated boron nitride nanotubes. B2: Add amino-modified boron nitride nanotubes to anhydrous ethanol and sonicate for 2-3 hours. Then add 4-formylphenylboronic acid pinacol ester and sonicate for 60-70 minutes. Stir at 70-80℃ for 12-14 hours. After cooling to 0℃, add sodium borohydride while stirring and stir at 25-30℃ for 6-7 hours. Centrifuge, wash the precipitate, and dry to obtain modified boron nitride nanotubes.

[0011] Preferably, the ratio of anhydrous toluene, boron nitride nanotubes, 3-glycidyl etheroxypropylmethyldiethoxysilane, deionized water, and glacial acetic acid in B1 is 280-300 mL: 2 g: 6 mL: 0.8 mL: 0.1 g.

[0012] Preferably, the ratio of anhydrous ethanol, amino boron nitride nanotubes, pinacol 4-formylphenylboronic acid ester, and sodium borohydride in B2 is 200-220 mL: 2 g: 5 g: 1 g.

[0013] A method for preparing a highly wear-resistant and flame-retardant thermoplastic elastomer includes the following steps: A composite flame retardant, modified boron nitride nanotubes, polytetrafluoroethylene micro powder, antioxidant 1010, and light stabilizer 770 are added to an ethylene-octene copolymer and premixed at 1000-1200 r / min for 10-15 min. Then, the copolymer is melt-blended in a twin-screw extruder. The extrudate is water-cooled, pelletized, and dried to obtain a highly wear-resistant and flame-retardant thermoplastic elastomer.

[0014] Preferably, during melt blending, the temperature of the twin-screw extruder is 110-120℃ in zone one, 130-135℃ in zone two, 140-145℃ in zone three, 135-140℃ in zone four, 130-135℃ in the die head, and 250-300 r / min.

[0015] The beneficial effects of this invention are: This invention provides a highly wear-resistant and flame-retardant thermoplastic elastomer and its preparation method. This invention simultaneously improves the wear resistance, flame retardancy, water resistance, tensile strength, and aging resistance of polyolefin thermoplastic elastomers through the following method.

[0016] (1) The phosphorus heterocyclic structure derived from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in the composite flame retardant of the present invention decomposes at high temperature to generate acidic substances such as phosphoric acid and metaphosphoric acid, which catalyze the dehydration and cross-linking reaction of the ethylene-octene copolymer matrix, thereby promoting the formation of an expanded and dense carbon layer. The dense carbon layer can act as a physical barrier to hinder heat transfer and oxygen diffusion, and can also effectively block heat transfer and the diffusion and exchange of oxygen and combustible gases, thus playing a condensed phase flame retardant role. At the same time, the dithiodiglycolic acid structure introduced in the composite flame retardant will release sulfur-containing free radicals during pyrolysis, which can accurately capture high-energy active free radicals in the flame gas phase, interrupt the combustion chain reaction, and form a gas phase flame retardant effect. The condensed phase carbonization of phosphorus and the gas phase quenching of sulfur form a complementary synergy, which significantly improves the overall flame retardant efficiency of the composite material. In addition, the phosphorus oxygen free radicals generated during the decomposition of the phosphorus flame retardant can also help quench active free radicals in the flame, further enhancing the gas phase flame retardant effect. The composite flame retardant has good compatibility with the ethylene-octene copolymer matrix. After being uniformly dispersed, it can fill the micro gaps in the matrix, improve the surface hardness and scratch resistance of the material, and reduce plastic deformation during the wear process.

[0017] (2) This invention significantly reduces the aggregation tendency of boron nitride nanotubes through amylation and borate ester grafting modification, and improves their dispersion uniformity and interfacial bonding strength in the ethylene-octene copolymer matrix. The modified boron nitride nanotubes are one-dimensional nanotube structures with high hardness and high elastic modulus. As a nano-reinforcing phase dispersed in the matrix, they can effectively resist indentation damage and plastic deformation during friction, and reduce material surface peeling. At the same time, their layered crystal structure gives them excellent self-lubricating properties, and interlayer slippage easily occurs during friction, reducing the interfacial friction coefficient. This effect synergizes with polytetrafluoroethylene micropowder to construct a dual mechanism of polytetrafluoroethylene surface lubrication and friction reduction and boron nitride nanotube matrix wear resistance enhancement, significantly optimizing the wear resistance of the material. During combustion, modified boron nitride nanotubes can construct a rigid nanoskeleton within the char layer formed by the composite flame retardant, enhancing the structural integrity and mechanical strength of the char layer and preventing early cracking and collapse. Simultaneously, the one-dimensional tubular structure of the boron nitride nanotubes physically extends the diffusion path of heat, oxygen, and combustible decomposition products, hindering the spread of flames into the matrix. This, combined with the catalytic char formation and gas-phase quenching of the composite flame retardant, creates a complementary synergy between physical and chemical processes, as well as condensed and gas-phase processes, further improving overall flame retardant performance. Modification with 3-glycidyl etheroxypropylmethyldiethoxysilane not only reduces the surface energy of the boron nitride nanotubes but also introduces hydrophobic alkyl chains that reduce hydrophilic sites on the composite material surface, thereby decreasing the material's ability to adsorb moisture. Well-dispersed and tightly bonded boron nitride nanotubes can effectively transfer and share external loads while hindering the initiation and propagation of microcracks within the matrix, thus improving the tensile strength and elastic modulus of the material and optimizing its resistance to deformation. Modified boron nitride nanotubes do not degrade at high temperatures, thus maintaining the integrity of the matrix structure. They can also hinder the diffusion of heat and oxygen into the matrix, reducing the rate of thermo-oxidative degradation. Furthermore, they can synergize with antioxidant 1010 and light stabilizer 770 to reduce the probability of free radicals contacting the matrix molecular chains, slowing down the degradation process and thus improving aging resistance.

[0018] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

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

[0020] Unless otherwise specified, the following information pertains to some of the raw materials used in the following embodiments and comparative examples of this invention: The ethylene-octene copolymer was purchased from Dongguan Zhangmutou Keruida Plastics Business Department, grade: 8440; the polytetrafluoroethylene micro powder was purchased from Shanghai Kanglang Biotechnology Co., Ltd., item number: KL816159.

[0021] Example 1: A method for preparing a highly wear-resistant and flame-retardant thermoplastic elastomer is as follows: S1: Add 13.8g of butyl acrylate to 100mL of anhydrous tetrahydrofuran and stir for 10min to obtain a butyl acrylate solution; S2: 29.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 0.5 g of triethylamine were added to 150 mL of anhydrous tetrahydrofuran and stirred for 30 min under a nitrogen atmosphere. Then, 100 mL of butyl acrylate solution was added dropwise at 0 °C at 2 mL / min and stirred for 50 min. The mixture was then refluxed at 66 °C for 10 h. 80% of the tetrahydrofuran was removed by vacuum distillation at 40 °C and 0.09 MPa. 200 mL of n-hexane was then added and ultrasonically dispersed for 20 min. Finally, the mixture was allowed to stand at -20 °C for 20 h to crystallize. The mixture was then filtered and the filter cake was washed twice with cold n-hexane at -20 °C. The mixture was then vacuum dried at 40 °C for 24 h to obtain a phosphorus-containing flame retardant. S3: 15.3g of dithiodiglycolic acid, 0.5g of 4-dimethylaminopyridine, and 250mL of anhydrous toluene were added to 34.2g of phosphorus-containing flame retardant and stirred for 30min under a nitrogen atmosphere. Then, 19.6g of N,N'-dicyclohexylcarbodiimide was slowly added and reacted at 0-5℃ for 2.5h. After filtering to remove the precipitate, the mixture was reacted at 20℃ for 12h. The temperature was then raised to 80℃ and filtered while hot. After the filtrate was cooled to room temperature, it was washed twice with saturated sodium chloride aqueous solution and then twice with deionized water. The pH of the organic phase was adjusted to 6.5 with 0.1mol / L hydrochloric acid, and the mixture was allowed to stand for 30min and separated. Finally, the organic phase was dried with 5% anhydrous magnesium sulfate for 4h, filtered, and the toluene was removed by rotary evaporation under reduced pressure at 60℃ and 0.09MPa to obtain the composite flame retardant. S4: 2 g of boron nitride nanotubes were added to 280 mL of anhydrous toluene and ultrasonically dispersed for 2 h. Then, under a nitrogen atmosphere, 6 mL of 3-glycidyl etheroxypropylmethyldiethoxysilane, 0.8 mL of deionized water, and 0.1 g of glacial acetic acid were added and refluxed at 110 °C for 16 h. After cooling, the mixture was centrifuged and the precipitate was washed three times each with toluene, ethanol, and deionized water. Finally, the precipitate was vacuum dried at 80 °C for 10 h to obtain amino-modified boron nitride nanotubes. S5: Add 2g of amino boron nitride nanotubes to 200mL of anhydrous ethanol and sonicate for 2h. Then add 5g of 4-formylphenylboronic acid pinacol ester and sonicate for 60min. Stir at 70℃ for 12h. After cooling to 0℃, add 1g of sodium borohydride in 5 portions (10min intervals each) while stirring and stir at 25℃ for 6h. Centrifuge to separate the precipitate and wash it 3 times each with ethanol and deionized water. Finally, vacuum dry at 60℃ for 20h to obtain modified boron nitride nanotubes. S6: Add 8g of composite flame retardant, 2g of modified boron nitride nanotubes, 4g of polytetrafluoroethylene micro powder, 0.5g of antioxidant 1010, and 0.5g of light stabilizer 770 to 100g of ethylene-octene copolymer and premix at 1000r / min for 10min. Then, melt blend in a twin-screw extruder at zone 1 temperature of 110℃, zone 2 temperature of 130℃, zone 3 temperature of 140℃, zone 4 temperature of 135℃, die head temperature of 130℃, and screw speed of 250r / min. After water cooling and pelletizing, the extrudate is dried at 80℃ for 4h to obtain a highly wear-resistant and flame-retardant thermoplastic elastomer.

[0022] Example 2: A method for preparing a highly wear-resistant and flame-retardant thermoplastic elastomer is as follows: S1: Add 13.8 g of butyl acrylate to 105 mL of anhydrous tetrahydrofuran and stir for 13 min to obtain a butyl acrylate solution; S2: 29.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 0.5 g of triethylamine were added to 150 mL of anhydrous tetrahydrofuran and stirred for 35 min under a nitrogen atmosphere. Then, 105 mL of butyl acrylate solution was added dropwise at 3 °C at 2 mL / min and stirred for 55 min. The mixture was then refluxed at 67 °C for 11 h. 83% of the tetrahydrofuran was removed by vacuum distillation at 40 °C and 0.09 MPa. 200 mL of n-hexane was then added and ultrasonically dispersed for 25 min. Finally, the mixture was allowed to stand at -20 °C for 22 h to crystallize. The mixture was then filtered and the filter cake was washed three times with cold n-hexane at -20 °C. The mixture was then vacuum dried at 40 °C for 24 h to obtain a phosphorus-containing flame retardant. S3: Add 15.3g of dithiodiglycolic acid, 0.5g of 4-dimethylaminopyridine, and 260mL of anhydrous toluene to 34.2g of phosphorus-containing flame retardant and stir for 40min under a nitrogen atmosphere. Then slowly add 19.6g of N,N'-dicyclohexylcarbodiimide and react at 3℃ for 2.5-3h. After filtering to remove the precipitate, react at 23℃ for 14h. Then heat to 85℃ and filter while hot. After cooling the filtrate to room temperature, wash twice with saturated sodium chloride aqueous solution and then wash three times with deionized water. Adjust the pH of the organic phase to 6.8 with 0.1mol / L hydrochloric acid, let stand for 40min and separate the liquids. Finally, dry the organic phase with 6% anhydrous magnesium sulfate for 5h, filter, and remove toluene by rotary evaporation under reduced pressure at 60℃ and 0.09MPa to obtain the composite flame retardant. S4: 2 g of boron nitride nanotubes were added to 290 mL of anhydrous toluene and ultrasonically dispersed for 2.5 h. Then, under a nitrogen atmosphere, 6 mL of 3-glycidyl etheroxypropylmethyldiethoxysilane, 0.8 mL of deionized water, and 0.1 g of glacial acetic acid were added and refluxed at 110 °C for 17 h. After cooling, the mixture was centrifuged and the precipitate was washed three times each with toluene, ethanol, and deionized water. Finally, the precipitate was vacuum dried at 80 °C for 11 h to obtain amino-modified boron nitride nanotubes. S5: 2g of amino boron nitride nanotubes were added to 210mL of anhydrous ethanol and ultrasonically dispersed for 2.5h. Then, 5g of 4-formylphenylboronic acid pinacol ester was added and ultrasonically dispersed for 65min. After stirring at 75℃ for 13h, the mixture was cooled to 0℃ and 1g of sodium borohydride was added in 5 portions (10min intervals each) while stirring. The mixture was stirred at 28℃ for 6.5h. The precipitate was separated by centrifugation and washed 4 times each with ethanol and deionized water. Finally, the precipitate was vacuum dried at 60℃ for 22h to obtain modified boron nitride nanotubes. S6: Add 9g of composite flame retardant, 2.5g of modified boron nitride nanotubes, 4.5g of polytetrafluoroethylene micro powder, 0.55g of antioxidant 1010, and 0.55g of light stabilizer 770 to 110g of ethylene-octene copolymer and premix at 1100r / min for 13min. Then, melt blend in a twin-screw extruder at zone 1 temperature of 115℃, zone 2 temperature of 133℃, zone 3 temperature of 143℃, zone 4 temperature of 138℃, die head temperature of 133℃, and screw speed of 280r / min. After water cooling and pelletizing, the extrudate is dried at 80℃ for 5h to obtain a highly wear-resistant and flame-retardant thermoplastic elastomer.

[0023] Example 3: A method for preparing a highly wear-resistant and flame-retardant thermoplastic elastomer is as follows: S1: Add 13.8g of butyl acrylate to 110mL of anhydrous tetrahydrofuran and stir for 15min to obtain a butyl acrylate solution; S2: 29.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 0.5 g of triethylamine were added to 150 mL of anhydrous tetrahydrofuran and stirred for 40 min under a nitrogen atmosphere. Then, 110 mL of butyl acrylate solution was added dropwise at 2 mL / min at 5 °C and stirred for 60 min. The mixture was then refluxed at 68 °C for 12 h. 85% of the tetrahydrofuran was removed by vacuum distillation at 40 °C and 0.09 MPa. 200 mL of n-hexane was then added and ultrasonically dispersed for 30 min. Finally, the mixture was allowed to stand at -20 °C for 24 h to crystallize. The mixture was then filtered and the filter cake was washed three times with cold n-hexane at -20 °C. The mixture was then vacuum dried at 40 °C for 24 h to obtain a phosphorus-containing flame retardant. S3: 15.3g of dithiodiglycolic acid, 0.5g of 4-dimethylaminopyridine, and 270mL of anhydrous toluene were added to 34.2g of phosphorus-containing flame retardant and stirred for 50min under a nitrogen atmosphere. Then, 19.6g of N,N'-dicyclohexylcarbodiimide was slowly added and reacted at 5℃ for 3h. After filtering to remove the precipitate, the mixture was reacted at 25℃ for 16h. The temperature was then raised to 90℃ and filtered while hot. After the filtrate was cooled to room temperature, it was washed twice with saturated sodium chloride aqueous solution and then four times with deionized water. The pH of the organic phase was adjusted to 7.0 with 0.1mol / L hydrochloric acid, and the mixture was allowed to stand for 50min and separated. Finally, the organic phase was dried with 8% anhydrous magnesium sulfate for 6h, filtered, and the toluene was removed by rotary evaporation under reduced pressure at 60℃ and 0.09MPa to obtain the composite flame retardant. S4: Add 2g of boron nitride nanotubes to 300mL of anhydrous toluene and sonicate for 3h. Then, under a nitrogen atmosphere, add 6mL of 3-glycidyl etheroxypropylmethyldiethoxysilane, 0.8mL of deionized water, and 0.1g of glacial acetic acid and reflux at 110℃ for 18h. After cooling, centrifuge to separate the precipitate. Then wash the precipitate three times each with toluene, ethanol, and deionized water. Finally, vacuum dry at 80℃ for 12h to obtain amino-modified boron nitride nanotubes. S5: Add 2g of amino boron nitride nanotubes to 220mL of anhydrous ethanol and sonicate for 3h. Then add 5g of 4-formylphenylboronic acid pinacol ester and sonicate for 70min. Then stir at 80℃ for 14h. After cooling to 0℃, add 1g of sodium borohydride in 5 portions (10min intervals each) while stirring and stir at 30℃ for 7h. Centrifuge to separate and wash the precipitate 5 times each with ethanol and deionized water. Finally, vacuum dry at 60℃ for 24h to obtain modified boron nitride nanotubes. S6: Add 10g of composite flame retardant, 3g of modified boron nitride nanotubes, 5g of polytetrafluoroethylene micro powder, 0.6g of antioxidant 1010, and 0.6g of light stabilizer 770 to 120g of ethylene-octene copolymer and premix at 1200r / min for 15min. Then, melt blend in a twin-screw extruder at zone 1 temperature of 120℃, zone 2 temperature of 135℃, zone 3 temperature of 145℃, zone 4 temperature of 140℃, die head temperature of 135℃, and screw speed of 300r / min. After water cooling and pelletizing, the extrudate is dried at 80℃ for 6h to obtain a highly wear-resistant and flame-retardant thermoplastic elastomer.

[0024] Comparative Example 1: Compared with Example 1, this comparative example only did not add "composite flame retardant" in the preparation process of S6. All other steps and parameters were the same, and will not be repeated here. The final result was a highly wear-resistant and flame-retardant thermoplastic elastomer.

[0025] Comparative Example 2: Compared with Example 1, this comparative example only omits the addition of "modified boron nitride nanotubes" in the preparation process of S6. All other steps and parameters are the same, and will not be repeated here. The final product is a highly wear-resistant and flame-retardant thermoplastic elastomer.

[0026] Performance testing: Abrasion resistance testing: Referring to GB / T 3960-2016 standard, the high wear-resistant and flame-retardant thermoplastic elastomers prepared in Examples 1-3 and Comparative Examples 1-2 of this invention were made into specimens with a size of 30mm×7mm×6mm, and the wear mass (mg) after 1000 revolutions at 100 rpm under a 5N load was measured. The measurement results are shown in Table 1.

[0027] Flame retardancy testing: Referring to GB / T 2408-2021 standard, the high wear-resistant and flame-retardant thermoplastic elastomers prepared in Examples 1-3 and Comparative Examples 1-2 of this invention were made into specimens with a thickness of 3.2 mm and the vertical burning flame retardancy rating (grade) was determined. The test results are shown in Table 1.

[0028] Water resistance testing: Referring to GB / T 1034-2008 standard, the water absorption rate (%) of the high wear-resistant and flame-retardant thermoplastic elastomers prepared in Examples 1-3 and Comparative Examples 1-2 of this invention was determined after immersion in deionized water at 25°C for 24 hours. The test results are shown in Table 1.

[0029] Determination of tensile strength: Referring to GB / T 528-2009 standard, the high wear-resistant and flame-retardant thermoplastic elastomers prepared in Examples 1-3 and Comparative Examples 1-2 of this invention were made into dumbbell-shaped specimens with a thickness of 6 mm, and the tensile strength (MPa) at a tensile rate of 500 mm / min was measured. The test results are shown in Table 1.

[0030] Determination of aging resistance: Referring to GB / T 3512-2014 standard, the tensile strength retention rate (%) of the high wear-resistant and flame-retardant thermoplastic elastomers prepared in Examples 1-3 and Comparative Examples 1-2 of this invention after being treated at 100℃ for 168h and cooled was determined. The test results are shown in Table 1.

[0031] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-2

[0032] Data Analysis: As can be seen from Table 1, the thermoplastic elastomer prepared in the embodiments of the present invention has excellent wear resistance, flame retardancy, water resistance, tensile strength and aging resistance.

[0033] In Comparative Example 1, no composite flame retardant was added during the preparation of the thermoplastic elastomer, and in Comparative Example 2, no modified boron nitride nanotubes were added. The flame retardancy of Comparative Example 1 was significantly reduced, indicating that the addition of the composite flame retardant in this invention can effectively improve the flame retardant effect. The wear resistance, flame retardancy, water resistance, tensile strength, and aging resistance of Comparative Example 2 were also significantly reduced, indicating that the addition of modified boron nitride nanotubes in this invention can effectively resist indentation damage and plastic deformation during friction, reduce material surface spalling, lower the interfacial friction coefficient, and improve material wear resistance; enhance the structural integrity and mechanical strength of the char layer during combustion, prolong the diffusion path of heat, oxygen, and combustible decomposition products, and improve flame retardancy; reduce hydrophilic sites on the surface of the composite material, improving water resistance; effectively transfer and share external loads, hinder the initiation and propagation of microcracks inside the matrix, and improve tensile strength; hinder the diffusion of heat and oxygen into the matrix, reduce the rate of thermo-oxidative degradation reaction, slow down the degradation process, and improve aging resistance.

[0034] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A highly wear-resistant and flame-retardant thermoplastic elastomer, characterized in that, The raw materials include the following parts by weight: 100-120 parts of ethylene-octene copolymer, 8-10 parts of composite flame retardant, 2-3 parts of modified boron nitride nanotubes, 4-5 parts of polytetrafluoroethylene micro powder, 0.5-0.6 parts of antioxidant 1010, and 0.5-0.6 parts of light stabilizer 770; The composite flame retardant is prepared from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, triethylamine, butyl acrylate, n-hexane, dithiodiglycolic acid, 4-dimethylaminopyridine, and N,N'-dicyclohexylcarbodiimide. The modified boron nitride nanotubes are prepared by first grafting boron nitride nanotubes with 3-glycidyl etheroxypropylmethyldiethoxysilane, and then grafting them with 4-formylphenylboronic acid pinacol ester.

2. The highly wear-resistant and flame-retardant thermoplastic elastomer according to claim 1, characterized in that, The preparation method of the composite flame retardant is as follows: A1: Add butyl acrylate to anhydrous tetrahydrofuran and stir for 10-15 min to obtain a butyl acrylate solution; A2: Add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triethylamine to anhydrous tetrahydrofuran and stir under a nitrogen atmosphere for 30-40 min. Then, add butyl acrylate solution dropwise at 0-5℃ and stir for 50-60 min. Then, reflux at 66-68℃ for 10-12 h. Remove 80%-85% of tetrahydrofuran by vacuum distillation. Then, add n-hexane and ultrasonically disperse for 20-30 min. Finally, let it stand at -20℃ for 20-24 h to crystallize. Filter and wash the filter cake with cold n-hexane at -20℃ and dry to obtain phosphorus-containing flame retardant. A3: Dithiodiglycolic acid, 4-dimethylaminopyridine, and anhydrous toluene are added to a phosphorus-containing flame retardant and stirred under a nitrogen atmosphere for 30-50 min. Then, N,N'-dicyclohexylcarbodiimide is added and reacted at 0-5℃ for 2.5-3 h. After filtering to remove the precipitate, the reaction is carried out at 20-25℃ for 12-16 h. Then, the temperature is raised to 80-90℃ and filtered. After cooling the filtrate, it is washed and the pH is adjusted to 6.5-7.

0. Then, it is allowed to stand for 30-50 min and separated. Finally, the organic phase is dried with anhydrous magnesium sulfate, filtered, and toluene is removed by rotary evaporation under reduced pressure to obtain the composite flame retardant.

3. The highly wear-resistant and flame-retardant thermoplastic elastomer according to claim 2, characterized in that, The ratio of anhydrous tetrahydrofuran to butyl acrylate described in A1 is 100-110 mL: 13.8 g.

4. The highly wear-resistant and flame-retardant thermoplastic elastomer according to claim 2, characterized in that, The ratio of anhydrous tetrahydrofuran, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, triethylamine, butyl acrylate solution, and n-hexane in A2 is 150 mL: 29.6 g: 0.5 g: 100-110 mL: 200 mL.

5. The highly wear-resistant and flame-retardant thermoplastic elastomer according to claim 2, characterized in that, The ratio of phosphorus-containing flame retardant, dithiodiglycolic acid, 4-dimethylaminopyridine, anhydrous toluene, and N,N'-dicyclohexylcarbodiimide described in A3 is 34.2g:15.3g:0.5g:250-270mL:19.6g.

6. The highly wear-resistant and flame-retardant thermoplastic elastomer according to claim 1, characterized in that, The modified boron nitride nanotubes are prepared as follows: B1: Add boron nitride nanotubes to anhydrous toluene and sonicate for 2-3 hours. Then, under a nitrogen atmosphere, add 3-glycidyl etheroxypropylmethyldiethoxysilane, deionized water, and glacial acetic acid and reflux at 110°C for 16-18 hours. After cooling, centrifuge, wash the precipitate, and dry to obtain aminated boron nitride nanotubes. B2: Add amino-modified boron nitride nanotubes to anhydrous ethanol and sonicate for 2-3 hours. Then add 4-formylphenylboronic acid pinacol ester and sonicate for 60-70 minutes. Stir at 70-80℃ for 12-14 hours. After cooling to 0℃, add sodium borohydride while stirring and stir at 25-30℃ for 6-7 hours. Centrifuge, wash the precipitate, and dry to obtain modified boron nitride nanotubes.

7. The highly wear-resistant and flame-retardant thermoplastic elastomer according to claim 6, characterized in that, The ratio of anhydrous toluene, boron nitride nanotubes, 3-glycidyl etheroxypropylmethyldiethoxysilane, deionized water, and glacial acetic acid in B1 is 280-300 mL: 2 g: 6 mL: 0.8 mL: 0.1 g.

8. The highly wear-resistant and flame-retardant thermoplastic elastomer according to claim 6, characterized in that, The ratio of anhydrous ethanol, amino-modified boron nitride nanotubes, pinacol 4-formylphenylboronic acid, and sodium borohydride in B2 is 200-220 mL: 2 g: 5 g: 1 g.

9. A method for preparing a highly wear-resistant and flame-retardant thermoplastic elastomer according to any one of claims 1-8, characterized in that, Includes the following steps: A composite flame retardant, modified boron nitride nanotubes, polytetrafluoroethylene micro powder, antioxidant 1010, and light stabilizer 770 are added to an ethylene-octene copolymer and premixed at 1000-1200 r / min for 10-15 min. Then, the copolymer is melt-blended in a twin-screw extruder. The extrudate is water-cooled, pelletized, and dried to obtain a highly wear-resistant and flame-retardant thermoplastic elastomer.

10. The method for preparing the highly wear-resistant and flame-retardant thermoplastic elastomer according to claim 9, characterized in that, During melt blending, the temperature of the twin-screw extruder is 110-120℃ in zone one, 130-135℃ in zone two, 140-145℃ in zone three, 135-140℃ in zone four, 130-135℃ in the die head, and the screw speed is 250-300 r / min.

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