Preparation method of high-strength flame-retardant PVC (Polyvinyl Chloride) based on modification of MOS (Metal Oxide Semiconductor) whiskers SiO2-CNT (Carbon Nanotube) composite filler

Abstract

The invention discloses a preparation method of high-strength flame-retardant PVC (Polyvinyl Chloride) based on modification of an MOS (Metal Oxide Semiconductor) whiskers-SiO2-CNT (Carbon Nano Tube) composite filler. The preparation method comprises the following steps: S1, preparing the MOS whiskers-SiO2-CNT composite filler; s2, carrying out functionalization treatment; s3, coating and modifying chlorinated polyethylene; and S4, mixing 100 parts by weight of PVC resin, 14-27 parts by weight of the MOS whiskers SiO2-CNT composite filler and 20-33 parts by weight of an auxiliary agent, and then pouring the mixture into a mixing mill for mixing to obtain the high-strength flame-retardant PVC. The PVC material modified based on the MOS whiskers SiO2-CNT composite filler prepared by the invention has excellent mechanical strength and flame retardant property, and also has very high oxidation resistance and thermal stability at the same time.

Description

TECHNICAL FIELD

[0001] The application relates to the field of high-strength flame-retardant PVC, and in particular to a preparation method of high-strength flame-retardant PVC based on MOS whisker-SiO2-CNT composite fillers. BACKGROUND

[0002] Polyvinyl chloride is a polymer material in which one hydrogen atom in polyethylene is replaced by one chlorine atom, and is an amorphous polymer containing a small amount of crystalline structure. PVC (polyvinyl chloride) has good comprehensive properties such as acid and alkali resistance, electrical insulation, mechanical properties and processing properties, and is widely used in light industry, construction, agriculture, power and daily life. Since the chlorine content in the structure of polyvinyl chloride is high, it has good flame retardant properties, but during the processing of polyvinyl chloride, a large amount of plasticizer is generally added for assistance, and the presence of these plasticizers greatly affects the flame retardant properties and high temperature resistance of polyvinyl chloride, resulting in a significant decrease in the flame retardant properties of polyvinyl chloride products, which requires the addition of flame retardants to improve its flame retardant properties. For example, the preparation method of a flame-retardant high-temperature-resistant PVC material disclosed in patent CN119912765B, the preparation method of a heat-resistant flame-retardant PVC material disclosed in patent CN119101313B, and the like.

[0003] In addition, the heat-oxidative aging resistance of polyvinyl chloride is relatively poor, and it is prone to degradation and aging under thermal-oxidative conditions, and small molecule hydrogen chloride (HCl) is removed, and the generated HCl will further catalyze the degradation of the carbon chain, ultimately leading to a decrease in performance.

[0004] In the previous work, the applicant used a composite modified filler based on graphene-coated hydroxyl magnesium aluminum hydrotalcite LDHs to modify PVC, which significantly improved the flame retardant properties of PVC (CN119286165B, a flame-retardant modified PVC composite material based on graphene-coated hydroxyl magnesium aluminum hydrotalcite LDHs and a preparation method thereof); but it did not conduct relevant research on the anti-aging properties of polyvinyl chloride, and it is necessary to provide more means to improve the flame retardant properties of polyvinyl chloride.

[0005] Therefore, it is necessary to improve the prior art to provide a more reliable solution. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a preparation method of high-strength flame-retardant PVC based on MOS whisker-SiO2-CNT composite fillers, which solves the problems in the prior art.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is: a preparation method of high-strength flame-retardant PVC based on MOS whisker-SiO2-CNT composite fillers, comprising the following steps: S1, preparing MOS whisker-SiO2-CNT composite filler: S1-1, taking mesoporous silica and MgSO4 and adding them into an ethanol aqueous solution, ultrasonic dispersion, to obtain dispersion liquid A; taking carbon nanotubes and MgCl2 and adding them into an ethanol aqueous solution, ultrasonic dispersion, to obtain dispersion liquid B; S1-2, under stirring, adding dispersion liquid A into dispersion liquid B, ultrasonic dispersion, then adding ammonia water dropwise to adjust pH to alkaline, stirring under heating, transferring the obtained mixture into a reaction kettle with a polytetrafluoroethylene liner, reaction at 200-230℃ for 2-6h, cooling, filtration, washing, drying, to obtain MOS whisker-SiO2-CNT composite particles; S2, functionalization treatment: adding MOS whisker-SiO2-CNT composite particles into an antioxidant solution, ultrasonic dispersion, then shaking table oscillation, suction filtration, washing, drying, to obtain functionalized MOS whisker-SiO2-CNT composite particles; S3, chlorinated polyethylene coating modification: S3-1, adding functionalized MOS whisker-SiO2-CNT composite particles into a silane coupling agent solution, stirring, suction filtration, washing, drying, to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, mixing pretreated functionalized MOS whisker-SiO2-CNT composite particles with chlorinated polyethylene at a mass ratio of 1: (1.2-3.5), mixing, to obtain MOS whisker-SiO2-CNT composite filler; S4, mixing 100 parts of PVC resin, 14-27 parts of MOS whisker-SiO2-CNT composite filler and 20-33 parts of auxiliary agent according to weight parts, then pouring into a mixing mill for mixing, to obtain high-strength flame-retardant PVC.

[0008] Preferably, the antioxidant in the antioxidant solution in step S2 is at least one selected from BHT, antioxidant CA, antioxidant 1010 and antioxidant 168, and the mass concentration of the antioxidant is 2-20%.

[0009] Preferably, the silane coupling agent solution in step S3-1 is an ethanol solution of KH-570, and the mass concentration is 5-12%.

[0010] Preferably, step S1 is specifically: S1-1, 0.6-2.4 g mesoporous silica, 0.36-1.44 g MgSO4 is added to an ethanol aqueous solution composed of 15-60 mL ethanol and 60-240 mL deionized water, ultrasonic dispersion for 40-120 min to obtain dispersion A; 1.0-4.0 g carbon nanotubes, 1.43-5.72 g MgCl2 is added to an ethanol aqueous solution composed of 30-120 mL ethanol and 120-480 mL deionized water, ultrasonic dispersion for 45-180 min to obtain dispersion B; S1-2, under stirring at 750-1500 rpm, dispersion A is added to dispersion B, ultrasonic dispersion for 30-12 min, then 5-20 wt% ammonia water is added dropwise to adjust pH to 9-11, stirring at 40-65 ℃, 500-1100 rpm for 45-180 min, the obtained mixture is transferred into a polytetrafluoroethylene lined reaction kettle, reaction at 200-230 ℃ for 2-6 h, cooling, filtration, washing, vacuum drying to obtain MOS whisker-SiO2-CNT composite particles.

[0011] Preferably, step S2 is specifically: 1.5-6 g MOS whisker-SiO2-CNT composite particles are added to 75-300 mL ethanol solution of antioxidant BHT with a concentration of 5-15 wt%, ultrasonic dispersion for 30-90 min, then shaking overnight at 50-70 ℃, suction filtration, the solid is washed with ethanol in turn, vacuum drying to obtain functionalized MOS whisker-SiO2-CNT composite particles.

[0012] Preferably, step S3 is specifically: S3-1, 0.5-2 g functionalized MOS whisker-SiO2-CNT composite particles are added to 20-80 mL ethanol solution of KH-570 with a concentration of 3.5-12 wt%, stirring at 50-70 ℃ for 2-4 h, suction filtration, ethanol washing, vacuum drying to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, the pretreated functionalized MOS whisker-SiO2-CNT composite particles are mixed with chlorinated polyethylene according to a mass ratio of 1: (1.2-3.5), and mixing at 160-180 ℃ for 10-40 min to obtain MOS whisker-SiO2-CNT composite filler.

[0013] Preferably, step S4 is specifically: 100 parts of PVC resin, 14-27 parts of MOS whisker-SiO2-CNT composite filler and 20-33 parts of auxiliary agent are mixed at 300-700 rpm, 70-90 ℃ for 15-60 min, then poured into a mixing machine and mixed at 165-175 ℃ for 10-20 min to obtain high-strength flame-retardant PVC; The auxiliary agent comprises, by weight, 0.8-3 parts of a heat stabilizer, 1.2-4 parts of a lubricant, and 18-26 parts of a plasticizer; The heat stabilizer is a calcium-zinc heat stabilizer. The lubricant is at least one of oxidized polyethylene wax, polyethylene wax, white carbon black, calcium carbonate, calcium stearate, or zinc stearate. The plasticizer is at least one of dioctyl terephthalate, diisooctyl phthalate, diisodecyl phthalate, glycerol trioleate, chlorinated paraffin, and epoxidized soybean oil.

[0014] Preferably, the mesoporous silica in step S1 is prepared by the following method: The cetylpyridinium chloride is added to a mixture of L deionized water and ethanol, stirred, and then ammonia water is added and stirred. Tetraethyl orthosilicate is added dropwise to the resulting mixture, stirred under heating, aged, centrifuged, washed, dried, and calcined to obtain mesoporous silica. The carbon nanotubes in step S1 are pretreated by the following method: the carbon nanotubes are added to a mixed acid composed of 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid, ultrasonically dispersed, then stirred and refluxed under heating, filtered, washed to neutral, and dried to complete the pretreatment.

[0015] Preferably, the mesoporous silica in step S1 is prepared by the following method: 0.34g of cetylpyridinium chloride is weighed and added to a mixture of 60mL of deionized water and 40mL of ethanol, stirred for 5min, then 1.5mL of ammonia water with a concentration of 20wt% is added and stirred for 10min. 4mL of tetraethyl orthosilicate is added dropwise to the resulting mixture, stirred at 40℃ for 3h, stopped stirring, aged at room temperature for 5h, centrifuged, and the solid product is sequentially washed with deionized water and ethanol, dried at 90℃ for 4h, and finally calcined at 550℃ for 4h to obtain mesoporous silica. The carbon nanotubes in step S1 are pretreated by the following method: the carbon nanotubes are added to a mixed acid composed of 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid in a volume ratio of 3:1, the solid-liquid mass ratio is controlled to be 1:90, ultrasonically dispersed for 60min, then stirred and refluxed at 70℃ for 6h, cooled to room temperature, filtered, washed with deionized water to neutral, and dried to complete the pretreatment.

[0016] Preferably, the preparation method of the high-strength flame-retardant PVC modified by the MOS whisker-SiO2-CNT composite filler comprises the following steps: S1, preparing MOS whisker-SiO2-CNT composite filler: S1-1, 1.2g mesoporous silica, 0.72g MgSO4 were added into an ethanol aqueous solution composed of 30mL ethanol and 120mL deionized water, and ultrasonic dispersion was carried out for 80min to obtain dispersion liquid A; 2.0g carbon nanotubes, 2.86g MgCl2 were added into an ethanol aqueous solution composed of 60mL ethanol and 240mL deionized water, and ultrasonic dispersion was carried out for 90min to obtain dispersion liquid B; S1-2, under stirring at 1200rpm, dispersion liquid A was added into dispersion liquid B, and ultrasonic dispersion was carried out for 60min, then 10wt% ammonia water was added dropwise to adjust pH to 11, stirring was carried out at 50℃ and 800rpm for 90min, the obtained mixture was transferred into a reaction kettle with a polytetrafluoroethylene liner, reaction was carried out at 210℃ for 3h, cooling was carried out to room temperature, filtration was carried out, deionized water and ethanol were sequentially used for washing, and vacuum drying was carried out at 90℃ for 12h to obtain MOS whisker-SiO2-CNT composite particles; S2, functionalization treatment: 3g MOS whisker-SiO2-CNT composite particles were added into 150mL ethanol solution of antioxidant BHT with a concentration of 10wt%, ultrasonic dispersion was carried out for 45min, then shaking was carried out at 60℃ overnight, suction filtration was carried out, the solid was sequentially washed with ethanol, and vacuum drying was carried out at 60℃ for 12h to obtain functionalized MOS whisker-SiO2-CNT composite particles; S3, chlorinated polyethylene coating modification: S3-1, 1g functionalized MOS whisker-SiO2-CNT composite particles were added into 40mL ethanol solution of KH-570 with a concentration of 7wt%, stirring was carried out at 60℃ for 3h, suction filtration was carried out, ethanol washing was carried out, and vacuum drying was carried out at 70℃ for 6h to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, the pretreated functionalized MOS whisker-SiO2-CNT composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and mixing was carried out at 170℃ for 20min to obtain MOS whisker-SiO2-CNT composite filler; S4, 100 parts of PVC resin, 21 parts of MOS whisker-SiO2-CNT composite filler and 26 parts of auxiliary agent were mixed at 500rpm and 80℃ for 30min, then were poured into a mixing machine, and mixing was carried out at 178℃ for 15min to obtain high-strength flame-retardant PVC; The auxiliary agent comprises: 1.5 parts by weight of heat stabilizer, 2.5 parts by weight of lubricant and 22 parts by weight of plasticizer.

[0017] The application has the following beneficial effects: The PVC material prepared based on the MOS whisker-SiO2-CNT composite filler modification has excellent mechanical strength and flame retardant performance, and also has high oxidation resistance and thermal stability performance. In the present application, by constructing the three inorganic reinforcing fillers into the composite of alkali magnesium sulfate whisker, carbon nanotube and mesoporous silica, the alkali magnesium sulfate whisker serves as an intermediate, so that the three inorganic reinforcing fillers form a variety of composite structures in the system: (1) carbon nanotube-alkali magnesium sulfate whisker-mesoporous silica composite structure, (2) carbon nanotube-alkali magnesium sulfate whisker-carbon nanotube composite structure, (3) mesoporous silica-alkali magnesium sulfate whisker-mesoporous silica composite structure. The alkali magnesium sulfate whisker is interwoven with the carbon nanotube, and the mesoporous silica serves as a connecting node, so that the three inorganic reinforcing fillers form a three-dimensional interpenetrating network structure, which can greatly improve the reinforcing effect of the three inorganic filler components (mesoporous silica, carbon nanotube, alkali magnesium sulfate whisker), at least including the improvement effect on mechanical strength, the improvement effect on thermal stability and the improvement effect on flame retardant performance. In the interpenetrating network structure, the nano mesoporous silica can serve as a network node and a bearing node, the fibrous alkali magnesium sulfate whisker serves as a linear bearing node, and the high aspect ratio carbon nanotube is interwoven with the alkali magnesium sulfate whisker to form a network structure, so that the improvement of the mechanical properties plays a synergistic enhancement effect, greatly improving the overall mechanical strength. At the same time, the nano silica and the carbon nanotube also have a synergistic enhancement effect on the improvement of thermal stability and the improvement of flame retardant performance of the carbon nanotube and the alkali magnesium sulfate whisker.

[0018] In the present application, by constructing the three inorganic reinforcing fillers into the composite of alkali magnesium sulfate whisker, carbon nanotube and mesoporous silica, the alkali magnesium sulfate whisker serves as an intermediate, so that the three inorganic reinforcing fillers form a variety of composite structures in the system: (1) carbon nanotube-alkali magnesium sulfate whisker-mesoporous silica composite structure, (2) carbon nanotube-alkali magnesium sulfate whisker-carbon nanotube composite structure, (3) mesoporous silica-alkali magnesium sulfate whisker-mesoporous silica composite structure. The alkali magnesium sulfate whisker is interwoven with the carbon nanotube, and the mesoporous silica serves as a connecting node, so that the three inorganic reinforcing fillers form a three-dimensional interpenetrating network structure, which can greatly improve the reinforcing effect of the three inorganic filler components (mesoporous silica, carbon nanotube, alkali magnesium sulfate whisker), at least including the improvement effect on mechanical strength, the improvement effect on thermal stability and the improvement effect on flame retardant performance. In the interpenetrating network structure, the nano mesoporous silica can serve as a network node and a bearing node, the fibrous alkali magnesium sulfate whisker serves as a linear bearing node, and the high aspect ratio carbon nanotube is interwoven with the alkali magnesium sulfate whisker to form a network structure, so that the improvement of the mechanical properties plays a synergistic enhancement effect, greatly improving the overall mechanical strength. At the same time, the nano silica and the carbon nanotube also have a synergistic enhancement effect on the improvement of thermal stability and the improvement of flame retardant performance of the carbon nanotube and the alkali magnesium sulfate whisker. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The antioxidant release performance test results of the functionalized MOS whisker-SiO2-CNT composite particles and MOS whisker-SiO2-CNT composite fillers prepared for Example 1; Figure 2 The tensile strength test results of the flame-retardant PVC prepared for Examples 1-4 and Comparative Examples 1-8; Figure 3 The bending strength test results of the flame-retardant PVC prepared for Examples 1-4 and Comparative Examples 1-8; Figure 4Results of tensile strength retention tests of the flame-retardant PVC prepared for Examples 1-4 and Comparative Examples 1-8; Figure 5 Results of limiting oxygen index tests of the flame-retardant PVC prepared for Examples 1-4 and Comparative Examples 1-8; Figure 6 Results of heat distortion temperature tests of the flame-retardant PVC prepared for Examples 1-4 and Comparative Examples 1-8. DETAILED DESCRIPTION

[0020] The application will be further described in conjunction with the examples below, so that those skilled in the art can implement the application according to the description and the examples.

[0021] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0022] The test methods used in the following examples are conventional methods unless otherwise specified. The materials and reagents used in the following examples are commercially available unless otherwise specified. The specific conditions are not specified in the following examples, and are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0023] The application provides a preparation method of high-strength flame-retardant PVC based on MOS whisker-SiO2-CNT composite filler modification, comprising the following steps: S1, preparing MOS whisker-SiO2-CNT composite filler, which is a composite of basic magnesium sulfate whisker, carbon nanotube and mesoporous silica, and the preparation method is as follows: S1-1, 0.6-2.4 g of mesoporous silica, 0.36-1.44 g of MgSO4 are added to an ethanol aqueous solution composed of 15-60 mL of ethanol and 60-240 mL of deionized water, and ultrasonic dispersion is carried out for 40-120 min to obtain dispersion liquid A; 1.0-4.0 g of carbon nanotube and 1.43-5.72 g of MgCl2 are added to an ethanol aqueous solution composed of 30-120 mL of ethanol and 120-480 mL of deionized water, and ultrasonic dispersion is carried out for 45-180 min to obtain dispersion liquid B; S1-2, under stirring at 750-1500 rpm, the dispersion A is added into the dispersion B, ultrasonic dispersion for 30-12 min, then 5-20 wt% ammonia water is added dropwise to adjust the pH to 9-11, stirring at 40-65 °C, 500-1100 rpm for 45-180 min, the obtained mixture is transferred into a reaction kettle with polytetrafluoroethylene lining, reaction at 200-230 °C for 2-6 h, cooling, filtration, washing, vacuum drying to obtain MOS whisker-SiO2-CNT composite particles.

[0024] S2, functionalization treatment: 1.5-6 g MOS whisker-SiO2-CNT composite particles are added into 75-300 mL antioxidant solution with a concentration of 5-15 wt%, ultrasonic dispersion for 30-90 min, then shaking overnight at 50-70 °C, suction filtration, the solid is washed with ethanol in turn, vacuum drying to obtain functionalized MOS whisker-SiO2-CNT composite particles.

[0025] S3, chlorinated polyethylene coating modification: S3-1, 0.5-2 g of functionalized MOS whisker-SiO2-CNT composite particles are added into 20-80 mL of ethanol solution of silane coupling agent solution with a concentration of 3.5-12 wt%, stirring at 50-70 °C for 2-4 h, suction filtration, ethanol washing, vacuum drying to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, the pretreated functionalized MOS whisker-SiO2-CNT composite particles are mixed with chlorinated polyethylene at a mass ratio of 1: (1.2-3.5), and mixing at 160-180 °C for 10-40 min to obtain MOS whisker-SiO2-CNT composite filler.

[0026] S4, 100 parts of PVC resin, 14-27 parts of MOS whisker-SiO2-CNT composite filler and 20-33 parts of auxiliary agent are mixed at 300-700 rpm, 70-90 °C for 15-60 min, then poured into a mixing machine and mixed at 165-175 °C for 10-20 min to obtain high-strength flame-retardant PVC; wherein, by weight, the auxiliary agent includes: heat stabilizer 0.8-3 parts, lubricant 1.2-4 parts, plasticizer 18-26 parts; The heat stabilizer is calcium-zinc heat stabilizer; The lubricant is at least one of oxidized polyethylene wax, polyethylene wax, white carbon black, calcium carbonate, calcium stearate or zinc stearate; The plasticizer is at least one of dioctyl terephthalate, diisooctyl phthalate, diisodecyl phthalate, triolein, chlorinated paraffin and epoxy soybean oil.

[0027] In a preferred embodiment, the antioxidant in the antioxidant solution in step S2 is selected from at least one of BHT, antioxidant CA, antioxidant 1010 and antioxidant 168, and the mass concentration of the antioxidant is 2-20%.

[0028] In a preferred embodiment, the silane coupling agent solution in step S3-1 is an ethanol solution of KH-570 with a mass concentration of 5-12%.

[0029] The mesoporous silica can be a conventional commercially available product or a self-made product. In a preferred embodiment, the mesoporous silica in step S1 is prepared by the following method: 0.34g of cetylpyridinium chloride was weighed into a mixture of 60mL of deionized water and 40mL of ethanol, stirred for 5min, then 1.5mL of 20wt% ammonia was added, stirred for 10min, 4mL of tetraethyl orthosilicate was added dropwise to the resulting mixture, stirred at 40℃ for 3h, stopped stirring, aged at room temperature for 5h, centrifuged, the solid product was washed with deionized water and ethanol in turn, dried at 90℃ for 4h, and finally calcined at 550℃ for 4h to obtain mesoporous silica.

[0030] In a preferred embodiment, the carbon nanotubes in step S1 are pretreated by the following method: the carbon nanotubes are added to a mixed acid composed of 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid in a volume ratio of 3:1, the solid-liquid mass ratio is controlled to be 1:90, ultrasonic dispersion is performed for 60min, then stirring reflux is performed at 70℃ for 6h, cooled to room temperature, filtered, washed with deionized water until neutral, and dried to complete the pretreatment.

[0031] Invention mechanism: In the present application, by adding MOS whisker-SiO2-CNT composite filler to PVC, the strength, flame retardant performance and anti-aging performance of PVC can be comprehensively improved. The preparation and mechanism of the MOS whisker-SiO2-CNT composite filler are described in detail below to facilitate understanding of the present application.

[0032] I. Preparation mechanism 1. First, mesoporous silica with rich pore structure is prepared by a conventional process, and carbon nanotubes are pretreated with strong acid composed of concentrated sulfuric acid and concentrated nitric acid to enrich the carboxyl functional groups on the surface of the carbon nanotubes, which is beneficial to the subsequent reaction. After that, by one-pot hydrothermal method, carbon nanotubes are used as and mesoporous silica as composite doping components to synthesize basic magnesium sulfate whisker, and then the basic magnesium sulfate whisker, carbon nanotubes and mesoporous silica are crosslinked to form a composite of the basic magnesium sulfate whisker, carbon nanotubes and mesoporous silica, that is, MOS whisker-SiO2-CNT composite particles. In this process, Mg 2+ The carboxyl groups on the carbon nanotubes and the silicon hydroxyl groups on the surface of the mesoporous silica are combined by electrostatic adsorption and / or coordination, and then the basic magnesium sulfate whisker MgSO4·5Mg(OH)2·3H2O is generated in the hydrothermal reaction process. The basic magnesium sulfate whisker can connect the carbon nanotubes and the mesoporous silica as a bridging component, and at the same time, the carbon nanotubes and the mesoporous silica can also be connected by the fibrous basic magnesium sulfate whisker, thereby forming various composite structures in the system: (1) carbon nanotube-basic magnesium sulfate whisker-mesoporous silica composite structure, (2) carbon nanotube-basic magnesium sulfate whisker-carbon nanotube composite structure, and (3) mesoporous silica-basic magnesium sulfate whisker-mesoporous silica composite structure.

[0033] 2. Then, by impregnation method, antioxidants are loaded in the lumen structure of the carbon nanotubes and the mesoporous structure of the mesoporous silica to realize functionalization treatment, and functionalized MOS whisker-SiO2-CNT composite particles are obtained; silane coupling agent KH-570 is used for surface modification treatment of the functionalized MOS whisker-SiO2-CNT composite particles to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles, and finally, chlorinated polyethylene is coated on the surface to obtain MOS whisker-SiO2-CNT composite filler.

[0034] II. Mechanism (1) Nano-silica can improve the tensile strength and toughness of PVC, and at the same time, it can delay the degradation of PVC material under light by absorbing or reflecting ultraviolet rays. In addition, nano-silica can also increase the thermal decomposition temperature of PVC and enhance the heat resistance.

[0035] (2) The addition of carbon nanotubes can improve the mechanical strength and thermal stability of PVC. On the other hand, the high aspect ratio and surface activity of carbon nanotubes can form a dense network to hinder the transfer of heat and oxygen to the substrate, delaying the spread of combustion. Through the action of adsorption and free radical capture, the surface of carbon nanotubes can adsorb free radicals (such as ·OH, ·H) generated during combustion, interrupt the chain reaction, and reduce the combustion rate.

[0036] (3) Basic magnesium sulfate whisker: MgSO4·5Mg(OH)2·3H2O is an excellent inorganic flame retardant, which can absorb a large amount of heat when decomposed at high temperature, reduce the surface temperature of the material, and delay the combustion process; it can release crystal water during the decomposition process, dilute the concentration of combustible gas, and inhibit the spread of flame; its decomposition products (such as MgO) can form a dense carbon layer on the surface of the material, which can isolate oxygen and reduce heat transfer. On the other hand, due to its fibrous structure, it plays a role in filling and strengthening in the system, and can also improve the mechanical strength of polyvinyl chloride.

[0037] (4) In the present application, by constructing mesoporous silica, carbon nanotubes, and basic magnesium sulfate whisker into a composite of basic magnesium sulfate whisker, carbon nanotube, and mesoporous silica, the basic magnesium sulfate whisker acts as an intermediate, allowing the three inorganic reinforcing fillers to form multiple composite structures in the system: (1) carbon nanotube-basic magnesium sulfate whisker-mesoporous silica composite structure, (2) carbon nanotube-basic magnesium sulfate whisker-carbon nanotube composite structure, (3) mesoporous silica-basic magnesium sulfate whisker-mesoporous silica composite structure. The basic magnesium sulfate whisker is interwoven with the carbon nanotube, and the mesoporous silica acts as a connecting node, allowing the three inorganic reinforcing fillers to form a three-dimensional interpenetrating network structure, which can greatly enhance the reinforcing effect of the three inorganic filler components (mesoporous silica, carbon nanotube, and basic magnesium sulfate whisker), including at least: the improvement of mechanical strength, the improvement of thermal stability, and the improvement of flame retardant performance. In this interpenetrating network structure, nano-mesoporous silica can act as a network node and a bearing node, fibrous basic magnesium sulfate whisker as a linear bearing node, and high-aspect-ratio carbon nanotubes interwoven with basic magnesium sulfate whisker to form a network structure, allowing the improvement of mechanical properties to have a synergistic enhancement effect, greatly improving the overall mechanical strength. At the same time, the improvement of thermal stability by nano-silica and carbon nanotubes, and the improvement of flame retardant performance by carbon nanotubes and basic magnesium sulfate whisker also have a synergistic enhancement effect.

[0038] (5) The three inorganic reinforcing fillers, basic magnesium sulfate whisker, carbon nanotube, and mesoporous silica, have poor compatibility with polyvinyl chloride when applied in polyvinyl chloride, which can cause the inorganic reinforcing fillers to be difficult to disperse uniformly, making it difficult to fully exert their reinforcing effect, and even causing negative effects. In the present application, by forming a composite system of basic magnesium sulfate whisker, carbon nanotube, and mesoporous silica, and then coating it with chlorinated polyethylene, which has good compatibility with PVC, the above-mentioned defects of the three inorganic reinforcing fillers can be solved, the compatibility between the three inorganic reinforcing fillers and the remaining polyvinyl chloride can be significantly improved, and the uniform dispersion of the three inorganic reinforcing fillers can be promoted. At the same time, chlorinated polyethylene can also improve the toughness of PVC to a certain extent.

[0039] (6) In the present application, the lumen structure of carbon nanotubes and the mesoporous structure of mesoporous silica are utilized, and further, the slow-release effect of the antioxidants loaded on the carbon nanotubes and mesoporous silica is realized through the cooperation of the polyvinyl chloride coating film (the antioxidants in the lumen structure of carbon nanotubes and the mesopores of mesoporous silica will be slowly released outward, and the polyvinyl chloride coating film has certain pores, and the released antioxidants can slowly overflow outward through these pores), so that long-acting antioxidant function can be provided for polyvinyl chloride, and the phenomena such as local aggregation and migration of antioxidants in polyvinyl chloride can be avoided, so that the premature failure of antioxidant function and the negative impact on the mechanical properties of polyvinyl chloride can be avoided. Further, the slow-release effect also has the effect of "self-adaptive regulation", when the temperature rises, the release rate of antioxidants in the lumen structure of carbon nanotubes and the mesoporous structure of mesoporous silica will increase due to the increase of molecular motion or thermal expansion and contraction, and the pores of the polyvinyl chloride coating film will increase due to thermal expansion and contraction or softening at high temperature, so as to increase the release rate of antioxidants, which can cope with the increased demand for antioxidants at high temperature (polyvinyl chloride is prone to thermal oxidative aging at high temperature, which can cause the polymer molecular chain to break and the mechanical strength to decrease).

[0040] The above is the overall concept of the present application, and the following provides detailed examples and comparative examples based thereon to further illustrate the present application.

[0041] Cetylpyridinium chloride, Nantong Runfeng Petroleum Chemical Co., Ltd.; Tetraethyl orthosilicate, Nanjing Chemical Reagent Co., Ltd.; Carbon nanotubes, multi-walled carbon nanotubes, diameter 60-100 nm, length 5-20 μm, Guangzhou Hongwu Material Technology Co., Ltd.; Antioxidant BHT, Jiangsu Xinluda Polymer Material Co., Ltd.; KH-570, Nanjing Xuanhao New Material Technology Co., Ltd.; PVC resin, grade 191#, Jiangsu Runfeng Synthetic Technology Co., Ltd.; Calcium-zinc heat stabilizer, SY-109 calcium-zinc stabilizer, Jiashan Sanyi New Material Co., Ltd.; Oxidized polyethylene wax, Haian Petroleum Chemical Plant of Jiangsu Province; Di-octyl terephthalate, Nanjing Chemical Reagent Co., Ltd.

[0042] Example 1 A preparation method of high-strength flame-retardant PVC modified based on MOS whisker-SiO2-CNT composite filler, comprising the following steps: S1, preparing MOS whisker-SiO2-CNT composite filler: S1-0, preparing mesoporous silica in advance: Take 0.34 g of cetylpyridine chloride into a mixture of 60 mL of deionized water and 40 mL of ethanol, stir for 5 min, then add 1.5 mL of 20 wt% ammonia water, stir for 10 min, add 4 mL of tetraethyl orthosilicate to the resulting mixture, stir at 40℃ for 3h, stop stirring, and let stand at room temperature for 5h, centrifuge, and wash the solid product with deionized water and ethanol, dry at 90℃ for 4h, and finally calcine at 550℃ for 4h to obtain mesoporous silica; The carbon nanotubes were pretreated by the following method: the carbon nanotubes were added to a mixed acid of 98 wt% concentrated sulfuric acid and 65 wt% concentrated nitric acid in a volume ratio of 3:1, the solid-liquid mass ratio was controlled to be 1:90, ultrasonic dispersion was performed for 60 min, then stirring reflux was performed at 70℃ for 6h, cooled to room temperature, filtered, washed with deionized water until neutral, and dried to complete the pretreatment.

[0043] S1-1, 1.2 g of mesoporous silica and 0.72 g of MgSO4 were added to an ethanol aqueous solution composed of 30 mL of ethanol and 120 mL of deionized water, ultrasonic dispersion was performed for 80 min to obtain dispersion liquid A; 2.0 g of carbon nanotubes and 2.86 g of MgCl2 were added to an ethanol aqueous solution composed of 60 mL of ethanol and 240 mL of deionized water, ultrasonic dispersion was performed for 90 min to obtain dispersion liquid B; S1-2, under stirring at 1200 rpm, dispersion liquid A was added to dispersion liquid B, ultrasonic dispersion was performed for 60 min, then 10 wt% ammonia water was added dropwise to adjust the pH to 11, stirring was performed at 50℃ and 800 rpm for 90 min, the resulting mixture was transferred into a polytetrafluoroethylene-lined reaction kettle, reaction was performed at 210℃ for 3h, cooled to room temperature, filtered, washed with deionized water and ethanol, and vacuum dried at 90℃ for 12h to obtain MOS whisker-SiO2-CNT composite particles; S2, functionalization treatment: 3 g of MOS whisker-SiO2-CNT composite particles were added to 150 mL of an ethanol solution of antioxidant BHT with a concentration of 10 wt%, ultrasonic dispersion was performed for 45 min, then shaking was performed at 60℃ overnight, suction filtration was performed, the solid was washed with ethanol, and vacuum drying was performed at 60℃ for 12h to obtain functionalized MOS whisker-SiO2-CNT composite particles; S3, chlorinated polyethylene coating modification: S3-1, 1 g of functionalized MOS whisker-SiO2-CNT composite particles were added to 40 mL of an ethanol solution of KH-570 with a concentration of 7 wt%, stirring was performed at 60℃ for 3h, suction filtration was performed, ethanol washing was performed, and vacuum drying was performed at 70℃ for 6h to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, mixing the pretreated functionalized MOS whisker-SiO2-CNT composite particles with chlorinated polyethylene at a mass ratio of 1:2.5, mixing at 170℃ for 20min, to obtain MOS whisker-SiO2-CNT composite filler; S4, mixing 100 parts of PVC resin, 21 parts of MOS whisker-SiO2-CNT composite filler and 26 parts of auxiliary agent (calcium-zinc heat stabilizer 1.5 parts, oxidized polyethylene wax 2.5 parts, dioctyl terephthalate 22 parts) by weight at 500rpm and 80℃ for 30min, then pouring into a mixer and mixing at 178℃ for 15min, to obtain high-strength flame-retardant PVC.

[0044] Example 2, a method for preparing high-strength flame-retardant PVC based on MOS whisker-SiO2-CNT composite filler modification, comprising the following steps: S1, preparing MOS whisker-SiO2-CNT composite filler: S1-0, preparing mesoporous silica in advance: Take 0.34g of chlorinated hexadecylpyridine and add it to a mixture of 60mL of deionized water and 40mL of ethanol, stir for 5min, then add 1.5mL of 20wt% ammonia, stir for 10min, add 4mL of tetraethyl orthosilicate to the resulting mixture, stir at 40℃ for 3h, stop stirring, let it stand at room temperature for 5h, centrifuge, wash the solid product with deionized water and ethanol, dry at 90℃ for 4h, and finally calcine at 600℃ for 3.5h, to obtain mesoporous silica; The carbon nanotubes are pretreated by the following method: add carbon nanotubes to a mixed acid composed of 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid at a volume ratio of 3:1, control the solid-liquid mass ratio to be 1:90, ultrasonic dispersion for 60min, then stir and reflux at 80℃ for 5h, cool to room temperature, filter, wash with deionized water until neutral, and dry, to complete the pretreatment.

[0045] S1-1, take 1.2g of mesoporous silica and 0.72g of MgSO4, add them to an ethanol aqueous solution composed of 30mL of ethanol and 120mL of deionized water, ultrasonic dispersion for 80min, to obtain dispersion A; take 2.0g of carbon nanotubes and 2.86g of MgCl2, add them to an ethanol aqueous solution composed of 60mL of ethanol and 240mL of deionized water, ultrasonic dispersion for 90min, to obtain dispersion B; S1-2, under stirring at 1200 rpm, the dispersion A was added into the dispersion B, ultrasonic dispersion for 60 min, then 10 wt% ammonia water was added dropwise to adjust the pH to 11, stirring at 50℃, 800 rpm for 90 min, the obtained mixture was transferred into a reaction kettle with polytetrafluoroethylene lining, reacted at 210℃ for 3 h, cooled to room temperature, filtered, washed with deionized water and ethanol in turn, and vacuum dried at 90℃ for 12 h to obtain MOS whisker-SiO2-CNT composite particles; S2, functionalization treatment: 3 g of MOS whisker-SiO2-CNT composite particles were added into 150 mL of 10 wt% ethanol solution of antioxidant BHT, ultrasonic dispersed for 45 min, then shaken overnight at 55℃, suction filtered, and the solid was washed with ethanol in turn, and vacuum dried at 60℃ for 12 h to obtain functionalized MOS whisker-SiO2-CNT composite particles; S3, chlorinated polyethylene coating modification: S3-1, 1 g of functionalized MOS whisker-SiO2-CNT composite particles were added into 40 mL of 7 wt% ethanol solution of KH-570, stirred at 60℃ for 3 h, suction filtered, washed with ethanol, and vacuum dried at 70℃ for 6 h to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, the pretreated functionalized MOS whisker-SiO2-CNT composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and kneaded at 170℃ for 20 min to obtain MOS whisker-SiO2-CNT composite filler; S4, 100 parts of PVC resin, 21 parts of MOS whisker-SiO2-CNT composite filler, and 26 parts of auxiliary agent (calcium-zinc heat stabilizer 1.5 parts, oxidized polyethylene wax 2.5 parts, dioctyl terephthalate 22 parts) were mixed at 500 rpm and 75℃ for 35 min, then poured into a kneader and kneaded at 178℃ for 15 min to obtain high-strength flame-retardant PVC.

[0046] Example 3 The difference between this example and Example 1 is only in step S4. In this example, step S4 is specifically: 100 parts of PVC resin, 19.5 parts of MOS whisker-SiO2-CNT composite filler, and 16 parts of auxiliary agent (calcium-zinc heat stabilizer 1.8 parts, oxidized polyethylene wax 3 parts, dioctyl terephthalate 13 parts) were mixed at 500 rpm and 75℃ for 35 min, then poured into a kneader and kneaded at 178℃ for 15 min to obtain high-strength flame-retardant PVC.

[0047] Example 4 A method for preparing high-strength flame-retardant PVC based on MOS whisker-SiO2-CNT composite filler modification, comprising the following steps: S1, Preparation of MOS whisker-SiO2-CNT composite filler: S1-0, Mesoporous silica is prepared in advance: 0.34 g of cetylpyridinium chloride was weighed into a mixture of 60 mL of deionized water and 40 mL of ethanol, stirred for 5 min, then 1.5 mL of 20 wt% ammonia water was added, stirred for 10 min, 4 mL of tetraethyl orthosilicate was added dropwise to the resulting mixture, stirred at 40°C for 3 h, stopped stirring, aged at room temperature for 5 h, centrifuged, and the solid product was washed with deionized water and ethanol in turn, dried at 90°C for 4 h, and finally calcined at 550°C for 4 h to obtain mesoporous silica; The carbon nanotubes are pretreated by the following method: the carbon nanotubes are added to a mixed acid of 98 wt% concentrated sulfuric acid and 65 wt% concentrated nitric acid in a volume ratio of 3:1, the solid-liquid mass ratio is controlled to be 1:90, ultrasonic dispersion is performed for 60 min, then stirring reflux is performed at 70°C for 6 h, cooled to room temperature, filtered, washed with deionized water until neutral, and dried to complete the pretreatment.

[0048] S1-1, 1.35 g of mesoporous silica and 0.72 g of MgSO4 were added to an ethanol aqueous solution composed of 30 mL of ethanol and 120 mL of deionized water, ultrasonic dispersion was performed for 80 min to obtain dispersion liquid A; 1.9 g of carbon nanotubes and 2.86 g of MgCl2 were added to an ethanol aqueous solution composed of 60 mL of ethanol and 240 mL of deionized water, ultrasonic dispersion was performed for 90 min to obtain dispersion liquid B; S1-2, under the stirring of 1200 rpm, dispersion liquid A was added to dispersion liquid B, ultrasonic dispersion was performed for 60 min, then 10 wt% ammonia water was added dropwise to adjust the pH to 11, stirring was performed at 50°C and 800 rpm for 90 min, the resulting mixture was transferred into a polytetrafluoroethylene-lined reaction kettle, reaction was performed at 210°C for 3 h, cooled to room temperature, filtered, washed with deionized water and ethanol in turn, and vacuum dried at 90°C for 12 h to obtain MOS whisker-SiO2-CNT composite particles; S2, functionalization treatment: 3 g of MOS whisker-SiO2-CNT composite particles were added to 150 mL of an ethanol solution of antioxidant BHT with a concentration of 10 wt%, ultrasonic dispersion was performed for 45 min, then shaking was performed at 60°C overnight, suction filtration was performed, the solid was washed with ethanol in turn, and vacuum drying was performed at 60°C for 12 h to obtain functionalized MOS whisker-SiO2-CNT composite particles; S3, chlorinated polyethylene coating modification: S3-1, 1 g of functionalized MOS whisker-SiO2-CNT composite particles was added into 40 mL of ethanol solution of KH-570 with a concentration of 7 wt%, stirred at 60°C for 3 h, suction filtered, washed with ethanol, and vacuum dried at 70°C for 6 h to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, the pretreated functionalized MOS whisker-SiO2-CNT composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.3, and then mixed at 170°C for 20 min to obtain MOS whisker-SiO2-CNT composite filler; S4, 100 parts of PVC resin, 21 parts of MOS whisker-SiO2-CNT composite filler, and 26 parts of auxiliary agent (calcium-zinc heat stabilizer 1.5 parts, oxidized polyethylene wax 2.5 parts, dioctyl terephthalate 22 parts) were mixed at 500 rpm and 80°C for 30 min, and then poured into a mixer and mixed at 178°C for 15 min to obtain high-strength flame-retardant PVC.

[0049] Comparative Example 1 The difference between this example and Example 1 is only that the MOS whisker-SiO2-CNT composite filler is replaced by the functionalized MOS whisker-SiO2-CNT composite particles prepared in step S2 of Example 1.

[0050] Comparative Example 2 A method for preparing high-strength flame-retardant PVC, comprising the following steps: S1, preparing MOS whisker-SiO2 composite particles: S1-0, mesoporous silica was prepared in advance, and the steps were the same as in Example 1; S1-1, 1.2 g of mesoporous silica and 0.72 g of MgSO4 were added into an ethanol aqueous solution composed of 30 mL of ethanol and 120 mL of deionized water, and ultrasonic dispersion was performed for 80 min to obtain dispersion liquid A; 2.86 g of MgCl2 was added into an ethanol aqueous solution composed of 60 mL of ethanol and 240 mL of deionized water, and ultrasonic dispersion was performed for 90 min to obtain dispersion liquid B; S1-2, under stirring at 1200 rpm, dispersion liquid A was added into dispersion liquid B, ultrasonic dispersion was performed for 60 min, then 10 wt% of ammonia water was added dropwise to adjust the pH to 11, stirring was performed at 50°C and 800 rpm for 90 min, the obtained mixture was transferred into a polytetrafluoroethylene-lined reaction kettle, reaction was performed at 210°C for 3 h, the temperature was cooled to room temperature, filtration was performed, deionized water and ethanol were sequentially used for washing, and vacuum drying was performed at 90°C for 12 h to obtain MOS whisker-SiO2 composite particles; S2, functionalization treatment: S3-2, the pretreated functional MOS whisker-SiO2 composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and mixed at 170°C for 20 min to obtain MOS whisker-SiO2 composite filler; S3, chlorinated polyethylene coating modification: S3-1, 1 g of functional MOS whisker-SiO2 composite particles was added to 40 mL of 7 wt% KH-570 ethanol solution, stirred at 60°C for 3 h, filtered, washed with ethanol, and dried at 70°C under vacuum for 6 h to obtain pretreated functional MOS whisker-SiO2 composite particles; S3-2, the pretreated functional MOS whisker-SiO2 composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and mixed at 170°C for 20 min to obtain MOS whisker-SiO2 composite filler; S4, 100 parts of PVC resin, 21 parts of MOS whisker-SiO2 composite filler, and 26 parts of auxiliary agent (calcium-zinc heat stabilizer 1.5 parts, oxidized polyethylene wax 2.5 parts, dioctyl terephthalate 22 parts) were mixed at 500 rpm and 80°C for 30 min, then poured into a mixer and mixed at 178°C for 15 min to obtain high-strength flame-retardant PVC.

[0051] Comparative Example 3 A method for preparing a high-strength flame-retardant PVC, comprising the following steps: S1, preparation of MOS whisker-CNT composite particles: S1-0, the carbon nanotubes were pretreated by the following method: carbon nanotubes were added to a mixed acid composed of 98 wt% concentrated sulfuric acid and 65 wt% concentrated nitric acid at a volume ratio of 3:1, the solid-liquid mass ratio was controlled at 1:90, ultrasonic dispersion was performed for 60 min, then stirring reflux was performed at 70°C for 6 h, cooled to room temperature, filtered, washed with deionized water until neutral, and dried to complete the pretreatment.

[0052] S1-1, 0.72 g of MgSO4 was added to 30 mL of ethanol and 120 mL of deionized water to form an ethanol aqueous solution, ultrasonic dispersion was performed for 80 min to obtain dispersion A; 2.0 g of carbon nanotubes and 2.86 g of MgCl2 were added to 60 mL of ethanol and 240 mL of deionized water to form an ethanol aqueous solution, ultrasonic dispersion was performed for 90 min to obtain dispersion B; S1-2, under stirring at 1200 rpm, the dispersion A was added into the dispersion B, ultrasonic dispersion for 60 min, then 10 wt% ammonia water was added dropwise to adjust the pH to 11, stirring at 50℃, 800 rpm for 90 min, the obtained mixture was transferred into a reaction kettle with polytetrafluoroethylene lining, and reacted at 210℃ for 3 h, cooled to room temperature, filtered, washed with deionized water and ethanol in turn, and vacuum dried at 90℃ for 12 h to obtain MOS whisker-CNT composite particles; S2, functionalization treatment: 3 g of MOS whisker-CNT composite particles were added into 150 mL of an ethanol solution of 10 wt% antioxidant BHT, ultrasonic dispersion for 45 min, then shaken overnight at 60℃, suction filtered, and the solid was washed with ethanol in turn, and vacuum dried at 60℃ for 12 h to obtain functionalized MOS whisker-CNT composite particles; S3, chlorinated polyethylene coating modification: S3-1, 1 g of functionalized MOS whisker-CNT composite particles were added into 40 mL of an ethanol solution of 7 wt% KH-570, stirred at 60℃ for 3 h, suction filtered, washed with ethanol, and vacuum dried at 70℃ for 6 h to obtain pretreated functionalized MOS whisker-CNT composite particles; S3-2, the pretreated functionalized MOS whisker-CNT composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and kneaded at 170℃ for 20 min to obtain MOS whisker-CNT composite filler; S4, 100 parts of PVC resin, 21 parts of MOS whisker-CNT composite filler, and 26 parts of auxiliary agent (1.5 parts of calcium-zinc heat stabilizer, 2.5 parts of oxidized polyethylene wax, and 22 parts of dioctyl terephthalate) were mixed at 500 rpm and 80℃ for 30 min, then poured into a kneader and kneaded at 178℃ for 15 min to obtain high-strength flame-retardant PVC.

[0053] Comparative Example 4, a method for preparing high-strength flame-retardant PVC, comprising the following steps: S1, mesoporous silica was prepared, the steps were the same as in Example 1; S2, the carbon nanotubes were pretreated by the following method: the carbon nanotubes were added into a mixed acid composed of 98 wt% concentrated sulfuric acid and 65 wt% concentrated nitric acid at a volume ratio of 3:1, the solid-liquid mass ratio was controlled to be 1:90, ultrasonic dispersion was performed for 60 min, then stirring reflux was performed at 70℃ for 6 h, cooled to room temperature, filtered, washed with deionized water until neutral, and dried to complete the pretreatment.

[0054] S3, MOS whisker preparation: S3-1, 0.72 g of MgSO4 was added to an ethanol aqueous solution composed of 30 mL of ethanol and 120 mL of deionized water, and ultrasonic dispersion was performed for 80 min to obtain dispersion liquid A; 2.86 g of MgCl2 was added to an ethanol aqueous solution composed of 60 mL of ethanol and 240 mL of deionized water, and ultrasonic dispersion was performed for 90 min to obtain dispersion liquid B; S3-2, under stirring at 1200 rpm, dispersion liquid A was added to dispersion liquid B, and ultrasonic dispersion was performed for 60 min, then 10 wt% ammonia water was added dropwise to adjust the pH to 11, and stirring was performed at 50℃ and 800 rpm for 90 min, the obtained mixture was transferred into a polytetrafluoroethylene-lined reaction kettle, and reaction was performed at 210℃ for 3 h, and then the mixture was cooled to room temperature, filtered, washed with deionized water and ethanol in sequence, and vacuum dried at 90℃ for 12 h to obtain MOS whiskers; S4, chlorinated polyethylene coating modification: S4-1, 0.2 g of mesoporous silica, 0.33 g of pretreated carbon nanotubes, and 0.47 g of MOS whiskers were added to 40 mL of an ethanol solution of KH-570 with a concentration of 7 wt%, and stirring was performed at 60℃ for 3 h, then suction filtration was performed, and ethanol washing and vacuum drying at 70℃ for 6 h were performed to obtain a pretreated particle composite; S4-2, the pretreated particle composite was mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and mixing was performed at 170℃ for 20 min to obtain a composite filler; S4, 100 parts of PVC resin, 19 parts of composite filler, 2 parts of antioxidant BHT, and 26 parts of auxiliary agent (1.5 parts of calcium-zinc heat stabilizer, 2.5 parts of oxidized polyethylene wax, and 22 parts of dioctyl terephthalate) were mixed at 500 rpm and 80℃ for 30 min, and then the mixture was poured into a mixing machine and mixed at 178℃ for 15 min to obtain high-strength flame-retardant PVC.

[0055] Comparative Example 5 A method for preparing high-strength flame-retardant PVC, comprising the following steps: S1, preparation of MOS whisker-CNT composite particles: S1-0, the carbon nanotubes were pretreated by the following method: the carbon nanotubes were added to a mixed acid composed of 98 wt% concentrated sulfuric acid and 65 wt% concentrated nitric acid at a volume ratio of 3:1, the solid-liquid mass ratio was controlled to be 1:90, ultrasonic dispersion was performed for 60 min, then stirring and reflux were performed at 70℃ for 6 h, the mixture was cooled to room temperature, filtered, washed with deionized water until neutral, and dried to complete the pretreatment.

[0056] S1-1, 0.72 g of MgSO4 was added to an ethanol aqueous solution composed of 30 mL of ethanol and 120 mL of deionized water, and ultrasonic dispersion was performed for 80 min to obtain a dispersion A; 2.0 g of carbon nanotubes and 2.86 g of MgCl2 were added to an ethanol aqueous solution composed of 60 mL of ethanol and 240 mL of deionized water, and ultrasonic dispersion was performed for 90 min to obtain a dispersion B; S1-2, under stirring at 1200 rpm, the dispersion A was added to the dispersion B, and ultrasonic dispersion was performed for 60 min, then 10 wt% ammonia water was added dropwise to adjust the pH to 11, and stirring was performed at 50℃ and 800 rpm for 90 min, the obtained mixture was transferred into a reaction kettle with a polytetrafluoroethylene liner, and reaction was performed at 210℃ for 3 h, and then the mixture was cooled to room temperature, filtered, washed with deionized water and ethanol in sequence, and vacuum dried at 90℃ for 12 h to obtain MOS whisker-CNT composite particles; S2, mesoporous silica was prepared as follows: 0.34 g of cetylpyridinium chloride was weighed and added to a mixture of 60 mL of deionized water and 40 mL of ethanol, and stirred for 5 min, then 1.5 mL of 20 wt% ammonia water was added, and stirred for 10 min, 4 mL of tetraethyl orthosilicate was added dropwise to the obtained mixture, and stirred at 40℃ for 3 h, the stirring was stopped, and the mixture was aged at room temperature for 5 h, centrifuged, and the solid product was washed with deionized water and ethanol in sequence, and dried at 90℃ for 4 h, and finally calcined at 550℃ for 4 h to obtain mesoporous silica; S3, functionalized mesoporous silica was prepared as follows: 3 g of mesoporous silica was added to 150 mL of an ethanol solution of antioxidant BHT with a concentration of 10 wt%, and ultrasonic dispersion was performed for 45 min, then shaken overnight at 60℃, and then suction filtered, and the solid was washed with ethanol in sequence, and vacuum dried at 60℃ for 12 h to obtain functionalized mesoporous silica; S4, chlorinated polyethylene coating modification: S4-1, 0.8 g of MOS whisker-CNT composite particles and 0.2 g of functionalized mesoporous silica were added to 40 mL of an ethanol solution of KH-570 with a concentration of 7 wt%, and stirred at 60℃ for 3 h, suction filtered, and washed with ethanol, and vacuum dried at 70℃ for 6 h to obtain pretreated composite particles; S4-2, the pretreated composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and then mixed at 170℃ for 20 min to obtain a composite filler; S45, 100 parts of PVC resin, 21 parts of composite filler, and 26 parts of auxiliary agent (1.5 parts of calcium-zinc heat stabilizer, 2.5 parts of oxidized polyethylene wax, and 22 parts of dioctyl terephthalate) were mixed at 500 rpm and 80℃ for 30 min, and then poured into a mixing machine and mixed at 178℃ for 15 min to obtain high-strength flame-retardant PVC.

[0057] Preparation method of a high-strength flame-retardant PVC, comprising the following steps: S1, preparation of MOS whisker-SiO2 composite particles: S1-0, mesoporous silica is prepared in advance: 0.34 g of cetylpyridinium chloride was weighed into a mixture of 60 mL of deionized water and 40 mL of ethanol, stirred for 5 min, then 1.5 mL of 20 wt% ammonia was added, stirred for 10 min, 4 mL of tetraethyl orthosilicate was added dropwise to the resulting mixture, stirred at 40°C for 3 h, stopped stirring, aged at room temperature for 5 h, centrifuged, the solid product was washed with deionized water and ethanol in turn, dried at 90°C for 4 h, and finally calcined at 550°C for 4 h to obtain mesoporous silica; S1-1, 1.2 g of mesoporous silica and 0.72 g of MgSO4 were added to an ethanol aqueous solution composed of 30 mL of ethanol and 120 mL of deionized water, and ultrasonic dispersion was performed for 80 min to obtain dispersion liquid A; 2.86 g of MgCl2 was added to an ethanol aqueous solution composed of 60 mL of ethanol and 240 mL of deionized water, and ultrasonic dispersion was performed for 90 min to obtain dispersion liquid B; S1-2, under stirring at 1200 rpm, dispersion liquid A was added to dispersion liquid B, ultrasonic dispersion was performed for 60 min, then 10 wt% ammonia was added dropwise to adjust the pH to 11, stirring was performed at 50°C and 800 rpm for 90 min, the resulting mixture was transferred into a polytetrafluoroethylene-lined reaction kettle, reaction was performed at 210°C for 3 h, cooled to room temperature, filtered, washed with deionized water and ethanol in turn, and vacuum dried at 90°C for 12 h to obtain MOS whisker-SiO2 composite particles; S2, functionalization treatment: 3 g of MOS whisker-SiO2 composite particles were added to 150 mL of an ethanol solution of 10 wt% antioxidant BHT, ultrasonic dispersion was performed for 45 min, then shaking was performed at 60°C overnight, suction filtration was performed, the solid was washed with ethanol in turn, and vacuum drying was performed at 60°C for 12 h to obtain functionalized MOS whisker-SiO2 composite particles; S3, chlorinated polyethylene coating modification: S3-0, the carbon nanotubes were pretreated by the following method: the carbon nanotubes were added to a mixed acid composed of 98 wt% concentrated sulfuric acid and 65 wt% concentrated nitric acid at a volume ratio of 3:1, the solid-liquid mass ratio was controlled to be 1:90, ultrasonic dispersion was performed for 60 min, then stirring reflux was performed at 70°C for 6 h, cooled to room temperature, filtered, washed with deionized water until neutral, and dried to complete the pretreatment.

[0058] S3-1, 0.67 g of functionalized MOS whisker-SiO2 composite particles and 0.33 g of pretreated carbon nanotubes were added to 40 mL of an ethanol solution of KH-570 with a concentration of 7 wt%, stirred at 60°C for 3 h, filtered, washed with ethanol, and vacuum dried at 70°C for 6 h to obtain pretreated composite particles; S3-2, the pretreated T composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and then mixed at 170°C for 20 min to obtain a composite filler; S4, 100 parts of PVC resin, 21 parts of composite filler, and 26 parts of auxiliary agent (1.5 parts of calcium-zinc heat stabilizer, 2.5 parts of oxidized polyethylene wax, and 22 parts of dioctyl terephthalate) were mixed at 500 rpm and 80°C for 30 min, and then poured into a mixer and mixed at 178°C for 15 min to obtain a high-strength flame-retardant PVC.

[0059] Comparative Example 7, a method for preparing a high-strength flame-retardant PVC, comprising the following steps: S1, MgO-SiO2-CNT composite particles were prepared: S1-0, mesoporous silica was prepared in advance, and the steps were the same as in Example 1; The carbon nanotubes were pretreated by the following method: the carbon nanotubes were added to a mixed acid composed of 98 wt% concentrated sulfuric acid and 65 wt% concentrated nitric acid at a volume ratio of 3:1, the solid-liquid mass ratio was controlled to be 1:90, ultrasonic dispersion was performed for 60 min, then stirring and reflux were performed at 70°C for 6 h, the temperature was cooled to room temperature, filtration was performed, deionized water was used for washing until neutral, and drying was performed, to complete the pretreatment.

[0060] S1-1, 1.2 g of mesoporous silica was added to an ethanol aqueous solution composed of 30 mL of ethanol and 120 mL of deionized water, and ultrasonic dispersion was performed for 80 min to obtain dispersion liquid A; 2.0 g of carbon nanotubes and 1.0 g of MgCl2 were added to an ethanol aqueous solution composed of 60 mL of ethanol and 240 mL of deionized water, and ultrasonic dispersion was performed for 90 min to obtain dispersion liquid B; S1-2, under stirring at 1200 rpm, dispersion liquid A was added to dispersion liquid B, ultrasonic dispersion was performed for 60 min, then 10 wt% ammonia water was added dropwise to adjust the pH to 11, stirring was performed at 50°C and 800 rpm for 90 min, the obtained mixture was transferred into a polytetrafluoroethylene-lined reaction kettle, reaction was performed at 210°C for 3 h, the temperature was cooled to room temperature, filtration was performed, deionized water and ethanol were used for washing in sequence, and vacuum drying was performed at 90°C for 12 h to obtain MgO-SiO2-CNT composite particles; S2, functionalization treatment: Functionalized MgO-SiO2-CNT composite particles were prepared by adding 3 g of MgO-SiO2-CNT composite particles to 150 mL of an ethanol solution of antioxidant BHT with a concentration of 10 wt%, ultrasonic dispersion for 45 min, then shaking overnight at 60°C, suction filtration, washing the solid with ethanol, and vacuum drying at 60°C for 12 h; S3, chlorinated polyethylene coating modification: S3-1, 1 g of functionalized MgO-SiO2-CNT composite particles was added to 40 mL of an ethanol solution of KH-570 with a concentration of 7 wt%, stirred at 60°C for 3 h, suction filtered, washed with ethanol, and vacuum dried at 70°C for 6 h to obtain pretreated functionalized MgO-SiO2-CNT composite particles; S3-2, the pretreated functionalized MgO-SiO2-CNT composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and mixed at 170°C for 20 min to obtain MgO-SiO2-CNT composite filler; S4, 100 parts of PVC resin, 21 parts of MgO-SiO2-CNT composite filler, and 26 parts of auxiliary agent (calcium-zinc heat stabilizer 1.5 parts, oxidized polyethylene wax 2.5 parts, dioctyl terephthalate 22 parts) were mixed at 500 rpm and 80°C for 30 min, then poured into a mixer and mixed at 178°C for 15 min to obtain high-strength flame-retardant PVC.

[0061] Comparative Example 8 The difference between this example and Comparative Example 7 is only in step S4, which is specifically: S4, 100 parts of PVC resin, 18.2 parts of MgO-SiO2-CNT composite filler, 2.8 parts of MOS whisker, and 26 parts of auxiliary agent (calcium-zinc heat stabilizer 1.5 parts, oxidized polyethylene wax 2.5 parts, dioctyl terephthalate 22 parts) were mixed at 500 rpm and 80°C for 30 min, then poured into a mixer and mixed at 178°C for 15 min to obtain high-strength flame-retardant PVC; The preparation method of the MOS whisker is the same as that of Comparative Example 4.

[0062] Comparative Example 9 A method for preparing high-strength flame-retardant PVC based on MOS whisker-SiO2-CNT composite filler modification, comprising the following steps: S1, preparing MOS whisker-SiO2-CNT composite filler, the steps are the same as those of Example 1; S2, chlorinated polyethylene coating modification: S2-1, 1 g MOS whisker-SiO2-CNT composite particles were added into 40 mL ethanol solution of KH-570 with a concentration of 7 wt%, stirred at 60 °C for 3 h, suction filtered, washed with ethanol, and vacuum dried at 70 °C for 6 h to obtain pretreated MOS whisker-SiO2-CNT composite particles; S2-2, the pretreated MOS whisker-SiO2-CNT composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and mixed at 170 °C for 20 min to obtain MOS whisker-SiO2-CNT composite filler; S3, 100 parts of PVC resin, 19 parts of MOS whisker-SiO2-CNT composite filler, 2 parts of antioxidant BHT, and 26 parts of additives (1.5 parts of calcium-zinc heat stabilizer, 2.5 parts of oxidized polyethylene wax, and 22 parts of dioctyl terephthalate) were mixed at 500 rpm and 80 °C for 30 min, then poured into a mixer and mixed at 178 °C for 15 min to obtain high-strength flame-retardant PVC.

[0063] Performance test I. Test the antioxidant release performance: Normal temperature group and high temperature group were set respectively: 5 g of sample was wrapped with a filter bag and placed in a glass dish, and the following operation was performed every 12 h: (1) Normal temperature group: add 60 mL of ethanol, seal and soak at 25 °C for 45 min, then rinse with ethanol for 3 times, take out, collect the rinse and soak liquid, combine, measure the total volume of the liquid, and detect the concentration of antioxidant BHT (determined by gas chromatography) to obtain the release amount; Functionalized MOS whisker-SiO2-CNT composite particles prepared in Example 1 (denoted as 1# sample) and MOS whisker-SiO2-CNT composite filler (denoted as 2# sample) were tested respectively.

[0064] (2) High temperature group: add 50 mL of ethanol, seal and soak at 90 °C for 60 min, then rinse with ethanol for 3 times, take out, collect the rinse and soak liquid, combine, measure the total volume of the liquid, and detect the concentration of antioxidant BHT (determined by gas chromatography) to obtain the release amount; MOS whisker-SiO2-CNT composite filler prepared in Example 1 (denoted as 3# sample) was tested.

[0065] The release curve was plotted with the cumulative release percentage as the vertical coordinate and the treatment time as the horizontal coordinate. Cumulative release percentage = Q tQ represents the cumulative release amount within t time, Q0 represents the total loading amount of antioxidant BHT (the calculation method is: the total mass of antioxidant BHT added in ethanol in step S2 of example 1 - the mass of antioxidant BHT remaining in ethanol after impregnation).

[0066] The test results are shown in Table 1. Figure 1 As can be seen from Table 1, the functionalized MOS whisker-SiO2-CNT composite particles prepared in example 1 (denoted as 1# sample) and the MOS whisker-SiO2-CNT composite filler (denoted as 2# sample) can both achieve slow release of antioxidant BHT, and the release rate of the latter is lower than that of the former; further, the test results of 3# sample can show that with the increase of temperature, the release rate of MOS whisker-SiO2-CNT composite filler for antioxidant BHT increases.

[0067] II. The flame-retardant PVC prepared in the examples and comparative examples was hot-pressed at 185℃ and 12MPa for 3min, and then cold-pressed at 15MPa for 3min on a flat vulcanizing machine, and then cut into a specified size to prepare test samples for subsequent performance testing: (1) Tensile strength: tested according to standard GB / T1040.1-2018; (2) Bending strength: tested according to standard GB / T 9341—2008; (3) Heat aging performance: heat aging was performed according to standard GBT7141-2008-Plastics Heat Aging Test Method, double 85 aging for 200h (85℃, RH=85%), and then the tensile strength and bending strength were tested again according to the above method, and the tensile strength retention rate was calculated: (tensile strength before aging / tensile strength after aging) x 100%.

[0068] (4) Limiting oxygen index (LOI): tested according to standard GB / T 2406—80; (5) Heat distortion temperature test: tested according to standard GB / T 1634. 3—2004.

[0069] The test results are shown in Table 1. Table 1 According to the test results, it can be concluded that: The PVC prepared in examples 1-4 has excellent mechanical strength and flame-retardant performance, and also has high antioxidant capacity and thermal stability, while the comparative examples 1-9 have different degrees of decline.

[0070] In the comparative example 1, the MOS whisker-SiO2-CNT composite filler is not coated with chlorinated polyethylene, so it is difficult to disperse uniformly in PVC, which seriously affects the reinforcing performance.

[0071] The composite filler in the comparative example 2 does not contain carbon nanotubes, which significantly reduces the mechanical strength and also loses the cavity structure of carbon nanotubes to load antioxidants, resulting in a significant decrease in anti-aging performance. The composite filler in the comparative example 3 does not contain porous silica, which reduces the anti-aging performance and mechanical strength. The results of the comparative examples 4-6 show that the three inorganic filler components (mesoporous silica, carbon nanotubes, and basic magnesium sulfate whiskers) in the MOS whisker-SiO2-CNT composite filler form a three-dimensional interpenetrating network structure, which can synergistically enhance the mechanical strength and flame retardant performance.

[0072] The composite filler in the comparative example 7 uses MgO instead of MOS whiskers, which is significantly worse than the MOS whisker-SiO2-CNT composite filler in improving mechanical properties and flame retardant properties. In the comparative example 8, MOS whiskers and MgO-SiO2-CNT composite fillers are added separately to the PVC raw material system, but the improvement effect is worse than that of the example 1, which is attributed to the failure to form the interpenetrating network structure in the example 1. In the comparative example 9, the antioxidant is directly added to the PVC, which does not have a slow-release performance, significantly weakening the anti-aging ability.

[0073] Although the embodiments of the present application have been disclosed as above, they are not limited to the application listed in the specification and embodiments, and can be fully applied to various fields suitable for the present application, and additional modifications can be easily realized by those skilled in the art, so the present application is not limited to specific details without departing from the general concept defined by the claims and equivalent scope.

Claims

1. A method for preparing high-strength flame-retardant PVC based on MOS whisker-SiO2-CNT composite filler modification, characterized in that, The method comprises the following steps: S1, preparing MOS whisker-SiO2-CNT composite filler: S1-1, taking mesoporous silica and MgSO4 and adding them into an ethanol aqueous solution, and ultrasonic dispersion to obtain a dispersion liquid A; taking carbon nanotubes and MgCl2 and adding them into an ethanol aqueous solution, and ultrasonic dispersion to obtain a dispersion liquid B; S1-2, under stirring, the dispersion liquid A is added into the dispersion liquid B, ultrasonic dispersion is performed, then ammonia water is added dropwise to adjust the pH to alkaline, stirring is performed under heating, the obtained mixture is transferred into a reaction kettle with a polytetrafluoroethylene liner, reaction is performed at 200-230 DEG C for 2-6 h, cooling is performed, filtration is performed, washing is performed, and drying is performed to obtain MOS whisker-SiO2-CNT composite particles; S2, functionalization treatment: The MOS whisker-SiO2-CNT composite particles are added into an antioxidant solution, ultrasonic dispersion is performed, then a shaker is shaken, suction filtration is performed, washing is performed, and drying is performed to obtain functionalized MOS whisker-SiO2-CNT composite particles; S3, chlorinated polyethylene coating modification: S3-1, the functionalized MOS whisker-SiO2-CNT composite particles are added into a silane coupling agent solution, stirring is performed, suction filtration is performed, washing is performed, and drying is performed to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, the pretreated functionalized MOS whisker-SiO2-CNT composite particles are mixed with chlorinated polyethylene at a mass ratio of 1: (1.2-3.5), and mixing is performed to obtain MOS whisker-SiO2-CNT composite filler; S4, 100 parts of PVC resin, 14-27 parts of MOS whisker-SiO2-CNT composite filler and 20-33 parts of auxiliary agent are mixed according to weight parts, then the mixture is poured into a mixing machine for mixing to obtain high-strength flame-retardant PVC.

2. The method for preparing high-strength flame-retardant PVC modified by MOS whisker-SiO2-CNT composite filler according to claim 1, characterized in that, The antioxidant in the antioxidant solution in step S2 is selected from at least one of BHT, antioxidant CA, antioxidant 1010 and antioxidant 168, and the mass concentration of the antioxidant is 2-20%.

3. The method for preparing high-strength flame-retardant PVC modified by MOS whisker-SiO2-CNT composite filler according to claim 1, characterized in that, The silane coupling agent solution in step S3-1 is an ethanol solution of KH-570, and the mass concentration is 5-12%.

4. The method for preparing high-strength flame-retardant PVC modified by MOS whisker-SiO2-CNT composite filler according to claim 1, characterized in that, Step S1 is specifically: S1-1, 0.6-2.4 g of mesoporous silica and 0.36-1.44 g of MgSO4 are added into an ethanol aqueous solution composed of 15-60 mL of ethanol and 60-240 mL of deionized water, and ultrasonic dispersion is performed for 40-120 min to obtain a dispersion liquid A; 1.0-4.0 g of carbon nanotubes and 1.43-5.72 g of MgCl2 are added into an ethanol aqueous solution composed of 30-120 mL of ethanol and 120-480 mL of deionized water, and ultrasonic dispersion is performed for 45-180 min to obtain a dispersion liquid B; S1-2, under stirring at 750-1500 rpm, the dispersion A is added into the dispersion B, ultrasonic dispersion for 30-12 min, then 5-20 wt% ammonia water is added dropwise to adjust pH to 9-11, stirring at 40-65 ℃, 500-1100 rpm for 45-180 min, the obtained mixture is transferred into a reaction kettle with a polytetrafluoroethylene liner, and reacted at 200-230 ℃ for 2-6 h, cooled, filtered, washed, and vacuum dried to obtain MOS whisker-SiO2-CNT composite particles.

5. The method for preparing high-strength flame-retardant PVC modified by MOS whisker-SiO2-CNT composite filler according to claim 1, characterized in that, Step S2 is specifically: 1.5-6 g MOS whisker-SiO2-CNT composite particles are added into 75-300 mL of an ethanol solution of antioxidant BHT with a concentration of 5-15 wt%, ultrasonic dispersion for 30-90 min, then shaken overnight at 50-70 ℃, suction filtered, the solid is washed with ethanol, and vacuum dried to obtain functionalized MOS whisker-SiO2-CNT composite particles.

6. The method for preparing high-strength flame-retardant PVC modified by MOS whisker-SiO2-CNT composite filler according to claim 1, characterized in that, Step S3 is specifically: S3-1, 0.5-2 g of the functionalized MOS whisker-SiO2-CNT composite particles are added into 20-80 mL of an ethanol solution of KH-570 with a concentration of 3.5-12 wt%, stirred at 50-70 ℃ for 2-4 h, suction filtered, washed with ethanol, and vacuum dried to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, the pretreated functionalized MOS whisker-SiO2-CNT composite particles are mixed with chlorinated polyethylene at a mass ratio of 1: (1.2-3.5), and mixed at 160-180 ℃ for 10-40 min to obtain MOS whisker-SiO2-CNT composite filler.

7. The method for preparing high-strength flame-retardant PVC modified by MOS whisker-SiO2-CNT composite filler according to claim 1, characterized in that, Step S4 is specifically: 100 parts of PVC resin, 14-27 parts of MOS whisker-SiO2-CNT composite filler, and 20-33 parts of additives are mixed at 300-700 rpm and 70-90 ℃ for 15-60 min, then poured into a mixing machine and mixed at 165-175 ℃ for 10-20 min to obtain high-strength flame-retardant PVC; wherein, according to weight parts, the additives include: 0.8-3 parts of heat stabilizer, 1.2-4 parts of lubricant, and 18-26 parts of plasticizer; the heat stabilizer is a calcium-zinc heat stabilizer; the lubricant is at least one of oxidized polyethylene wax, polyethylene wax, white carbon black, calcium carbonate, calcium stearate, or zinc stearate; the plasticizer is at least one of dioctyl terephthalate, diisooctyl phthalate, diisodecyl phthalate, glycerol trioleate, chlorinated paraffin, and epoxidized soybean oil.

8. The method for preparing high-strength flame-retardant PVC based on MOS whisker-SiO2-CNT composite filler modification according to any one of claims 1-7, characterized in that, The mesoporous silica in step S1 is prepared by the following method: hexadecylpyridinium chloride is added into a mixed solution of L deionized water and ethanol, stirred, ammonia water is added, stirred, and tetraethyl orthosilicate is added dropwise into the obtained mixture, stirred under heating, aged, centrifuged, washed, dried, and calcined to obtain mesoporous silica; The carbon nanotubes in step S1 are pretreated by the following method: carbon nanotubes are added to a mixed acid composed of 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid, ultrasonic dispersion, then stirring and refluxing under heating, filtering, washing to neutral, drying, completing the pretreatment.

9. The method for preparing high-strength flame-retardant PVC modified by MOS whisker-SiO2-CNT composite filler according to claim 8, characterized in that, The mesoporous silica in step S1 is prepared by the following method: 0.34g of cetylpyridinium chloride is weighed into a mixture of 60mL of deionized water and 40mL of ethanol, stirred for 5min, then 1.5mL of 20wt% ammonia water is added, stirred for 10min, 4mL of tetraethyl orthosilicate is added dropwise to the resulting mixture, stirred at 40℃ for 3h, stop stirring, room temperature for 5h, centrifugation, the solid product is washed with deionized water and ethanol in turn, dried at 90℃ for 4h, and finally calcined at 550℃ for 4h to obtain mesoporous silica; The carbon nanotubes in step S1 are pretreated by the following method: carbon nanotubes are added to a mixed acid composed of 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid, ultrasonic dispersion, then stirring and refluxing under heating, filtering, washing to neutral, drying, completing the pretreatment.

10. The method of preparing high strength flame retardant PVC based on MOS whisker-Si02-CNT composite filler modified according to claim 1, characterized in that, Comprising the following steps: S1, preparation of MOS whisker-SiO2-CNT composite filler: S1-1, 1.2g of mesoporous silica, 0.72g of MgSO4 is added to an ethanol aqueous solution composed of 30mL of ethanol and 120mL of deionized water, ultrasonic dispersion for 80min to obtain dispersion A; 2.0g of carbon nanotubes, 2.86g of MgCl2 is added to an ethanol aqueous solution composed of 60mL of ethanol and 240mL of deionized water, ultrasonic dispersion for 90min to obtain dispersion B; S1-2, under the stirring of 1200rpm, dispersion A is added to dispersion B, ultrasonic dispersion for 60min, then 10wt% ammonia water is added dropwise to adjust the pH to 11, stirring at 50℃ and 800rpm for 90min, the resulting mixture is transferred into a polytetrafluoroethylene lined reaction kettle, reacted at 210℃ for 3h, cooled to room temperature, filtered, washed with deionized water and ethanol in turn, vacuum dried at 90℃ for 12h to obtain MOS whisker-SiO2-CNT composite particles; S2, functionalization treatment: 3g of MOS whisker-SiO2-CNT composite particles is added to 150mL of 10wt% BHT ethanol solution, ultrasonic dispersion for 45min, then shaking overnight at 60℃, suction filtration, the solid is washed with ethanol in turn, vacuum dried at 60℃ for 12h to obtain functionalized MOS whisker-SiO2-CNT composite particles; S3, chlorinated polyethylene coating modification: S3-1, 1 g of functionalized MOS whisker-SiO2-CNT composite particles was added to 40 mL of ethanol solution of KH-570 with a concentration of 7 wt%, stirred at 60°C for 3 h, suction filtered, washed with ethanol, and vacuum dried at 70°C for 6 h to obtain pretreated functionalized MOS whisker-SiO2-CNT composite particles; S3-2, the pretreated functionalized MOS whisker-SiO2-CNT composite particles were mixed with chlorinated polyethylene at a mass ratio of 1:2.5, and then mixed at 170°C for 20 min to obtain MOS whisker-SiO2-CNT composite filler; S4, 100 parts of PVC resin, 21 parts of MOS whisker-SiO2-CNT composite filler and 26 parts of auxiliary were mixed at 500 rpm and 80°C for 30 min, and then poured into a mixing machine and mixed at 178°C for 15 min to obtain high-strength flame-retardant PVC; wherein the auxiliary includes: heat stabilizer 1.5 parts by weight, lubricant 2.5 parts by weight, plasticizer 22 parts by weight.

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