Composite board and preparation method thereof

Abstract

The invention provides a composite board and a preparation method thereof. The composite board sequentially comprises an inner layer containing polyvinyl chloride resin and a thermoplastic elastomer, a middle layer containing an ethylene-vinyl acetate copolymer and an outer layer containing a polyvinyl chloride resin foaming material from inside to outside. The composite board disclosed by the invention can meet the performance requirements in multiple aspects of low-temperature impact resistance, mechanical strength, aging resistance and the like.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a composite board and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC) is a polymer formed by the free radical polymerization of vinyl chloride monomer under the initiation of peroxides, azo compounds, or under the action of light and heat. PVC is a white powder, non-toxic and odorless, with low water absorption and air permeability. It is insoluble in water, gasoline, alcohol, and vinyl chloride, but soluble in ketones, esters, and chlorinated hydrocarbon solvents. PVC possesses advantages such as flame retardancy, chemical resistance, high mechanical strength, and good electrical insulation. PVC is widely used in electrical wire and cable insulation materials, artificial leather, floor tiles, toys, shoes, bottles, records, foam materials, sealing materials, and fibers.

[0003] Polyvinyl chloride (PVC), as a commonly used synthetic plastic, possesses excellent electrical insulation and corrosion resistance. However, it is prone to embrittlement at low temperatures, with its low-temperature resistance limited to around -15℃ to -20℃, and its impact resistance is poor. To meet the high requirements for cable sheath materials in cold regions and under special working conditions, low-temperature modifiers are commonly used to modify PVC. However, it is difficult to simultaneously meet the requirements for low-temperature impact resistance, mechanical strength, and aging resistance. Furthermore, the adhesives and plasticizers used in the modification process present cost and environmental pollution issues. Summary of the Invention

[0004] This invention provides a composite board and its preparation method, which takes into account multiple performance requirements such as low-temperature impact resistance, mechanical strength and aging resistance.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] The present invention provides a composite board, which, from the inside out, comprises an inner layer containing polyvinyl chloride resin and thermoplastic elastomer, an intermediate layer containing ethylene-vinyl acetate copolymer, and an outer layer containing polyvinyl chloride resin.

[0007] In this invention, polyvinyl chloride (PVC) resin is used as the base layer to ensure the mechanical strength and electrical insulation properties of the composite board. The thermoplastic elastomer (TPE) introduced into the inner layer can synergistically interact with the PVC resin molecular chains through an interpenetrating and compatible structure mainly composed of physical entanglement with flexible polymers, thereby improving chain segment mobility, lowering the glass transition temperature (Tg), and improving the low-temperature toughness of the composite board. Secondly, the fine cellular structure of the PVC resin foam material can effectively disperse impact energy, playing a role in heat insulation and buffering at low temperatures; in environments with large temperature variations, the cellular structure can delay heat conduction and reduce stress concentration. Furthermore, using molten ethylene-vinyl acetate copolymer (EVA) as a binder can achieve a strong bond between the inner and outer layers, improving the interfacial bonding strength and overall toughness of the composite board. At the same time, the interlayer compatibility between EVA and thermoplastic elastomer (TPE) is enhanced through van der Waals forces and certain polar interactions, further improving the low-temperature impact resistance.

[0008] Optionally, in the inner layer, the mass ratio of polyvinyl chloride resin to thermoplastic elastomer is 80-90:15-35, preferably 85-90:18-35.

[0009] Optionally, the inner layer further includes a first plasticizer, a first stabilizer, modified silica, and processing aids.

[0010] Optionally, the first plasticizer is selected from dioctyl phthalate or epoxidized soybean oil or a combination thereof. The mass ratio of the first plasticizer to the thermoplastic elastomer is 5-15:15-35, preferably 8-15:15-35.

[0011] In this invention, dioctyl phthalate (DOP) and epoxidized soybean oil (ESO) are used as plasticizers. They can intercalate between the molecular chains of polyvinyl chloride (PVC), increasing the intersegmental spacing, weakening the intermolecular forces, and thus reducing the mutual restraint between molecular chains, making the PVC molecular chains easier to slide relative to each other. As a result, it can maintain high flexibility and ductility even at low temperatures.

[0012] Optionally, the first stabilizer is selected from calcium-zinc stabilizers or lead salt stabilizers or a combination of both. The mass ratio of the first stabilizer to the thermoplastic elastomer is 2-8:15-35, preferably 3-8:15-35.

[0013] Optionally, the modified silica is selected from silane coupling agent modified silica. The mass ratio of the modified silica to the thermoplastic elastomer is 3-10:15-35, preferably 4-10:15-35.

[0014] In this invention, silane coupling agent modified silica can act as a cell nucleating agent, reducing the risk of cell coalescence and forming a finer, more uniform cell structure, thereby improving the impact resistance and thermal stability of the composite board.

[0015] Optionally, the processing aid is selected from at least one of ACR processing aid, butyl stearate, and glyceryl stearate. The mass ratio of the processing aid to the thermoplastic elastomer is 0.5-5:15-35, preferably 1-5:15-35.

[0016] Optionally, the intermediate layer further includes a peroxide crosslinking agent. The mass ratio of the peroxide crosslinking agent to the ethylene-vinyl acetate copolymer (EVA) is 0.1-3:100, preferably 0.5-1:100.

[0017] In this invention, under high temperature conditions, the peroxide crosslinking agent can thermally decompose to generate free radicals, which then undergo free radical crosslinking within the EVA layer and form limited grafting at the interface, thereby improving interfacial bonding and aging resistance, forming a crosslinked network structure, and improving the thermal stability and UV aging resistance of the composite board.

[0018] Optionally, the outer layer further includes a foaming agent, a second plasticizer, and a second stabilizer.

[0019] Optionally, the foaming agent is selected from azodicarbonyl foaming agents. The mass ratio of the foaming agent to the polyvinyl chloride resin is 5-8:60-70, preferably 6-8:60-70.

[0020] Optionally, the second plasticizer is selected from dioctyl phthalate or epoxidized soybean oil, or a combination of both. The mass ratio of the second plasticizer to the polyvinyl chloride resin is 20-30:60-70, preferably 25-30:60-70. The second stabilizer includes barium 2-ethylhexanoate, zinc ethylhexanoate, phosphite, 2,6-di-tert-butyl-p-cresol, bisphenol A antioxidant, ultraviolet absorber, liquid paraffin, and alcohol defoamer. By mass, the second stabilizer includes 6-7 parts of barium 2-ethylhexanoate, 0.5-1 part of zinc ethylhexanoate, 15-20 parts of phosphite, 0.5-2 parts of 2,6-di-tert-butyl-p-cresol, 0.5-2 parts of bisphenol A antioxidant, 1-3 parts of ultraviolet absorber, 2-5 parts of liquid paraffin, and 0.5-1 part of alcohol defoamer.

[0021] The present invention also provides a method for preparing the composite board as described above, comprising the following steps:

[0022] S1. Mix the polyvinyl chloride resin and the thermoplastic elastomer to obtain a mixture, melt-blend and extrude the mixture, cool and pelletize it to obtain inner layer composite particles; shape the inner layer composite particles by flat extrusion or calendering process, cool it to obtain inner layer sheet;

[0023] S2. The polyvinyl chloride resin is injection molded to obtain the outer layer sheet;

[0024] S3. The ethylene-vinyl acetate copolymer is coated on the surface of the inner layer sheet and the surface of the outer layer sheet respectively. The inner layer sheet and the outer layer sheet are bonded together by the ethylene-vinyl acetate copolymer in the molten state to obtain the composite sheet. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the composite material of the present invention;

[0026] Figure 2 The images shown are electron microscope (EM) images of each layer of the composite material prepared in Example 3, where a is the EEM image of the inner layer, b is the EEM image of the middle layer, and c is the EEM image of the outer layer.

[0027] The attached figures are labeled as follows:

[0028] 1-Outer layer, 2-Middle layer, 3-Inner layer. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0030] like Figure 1 As shown, this application provides a composite board, which, along the direction from the inside to the outside, sequentially includes an inner layer 3 containing polyvinyl chloride resin and thermoplastic elastomer, an intermediate layer 2 containing ethylene-vinyl acetate copolymer, and an outer layer 1 containing polyvinyl chloride resin foam.

[0031] In the inner layer, the mass ratio of polyvinyl chloride resin to thermoplastic elastomer is 80-90:15-35; the inner layer also includes a first plasticizer, a first stabilizer, modified silica and processing aids; the mass ratio of the first plasticizer to thermoplastic elastomer is 5-15:15-35, and the modified silica is selected from silane coupling agent modified silica;

[0032] The intermediate layer also includes a peroxide crosslinking agent;

[0033] By weight, the second stabilizer comprises 6-7 parts of barium 2-ethylhexanoate, 0.5-1 parts of zinc ethylhexanoate, 15-20 parts of phosphite, 0.5-2 parts of 2,6-di-tert-butyl-p-cresol, 0.5-2 parts of bisphenol A antioxidant, 1-3 parts of ultraviolet absorber, 2-5 parts of liquid paraffin, and 0.5-1 parts of alcohol defoamer.

[0034] The present invention also provides a method for preparing the composite board as described above, comprising the following steps:

[0035] S1. Mix polyvinyl chloride resin and the thermoplastic elastomer to obtain a mixture, melt-blend and extrude the mixture, cool and pelletize it to obtain inner layer composite particles; shape the inner layer composite particles by flat extrusion or calendering process, cool it to obtain inner layer sheet;

[0036] S2. Injection mold the polyvinyl chloride resin foam to obtain the outer sheet material;

[0037] S3. Ethylene-vinyl acetate copolymer is coated on the surface of the inner layer board and the surface of the outer layer board respectively. The inner layer board and the outer layer board are bonded together by the ethylene-vinyl acetate copolymer in the molten state to obtain a composite board.

[0038] Among them, 1 is the outer layer, 2 is the middle layer, and 3 is the inner layer.

[0039] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0040] Example 1

[0041] S1.1 Disperse 5g of silica powder in 100mL of anhydrous ethanol and sonicate for 30min to obtain a uniform suspension; under stirring, add 2g of γ-aminopropyltriethoxysilane (KH-550) and adjust the pH of the solution to 4 (using glacial acetic acid); react in a 60℃ water bath for 3h to allow the coupling agent to fully react with the hydroxyl groups on the silica surface; after the reaction, filter the product under vacuum, wash it with anhydrous ethanol and deionized water until neutral, and then dry it under vacuum at 80℃ for 12h to obtain silane coupling agent modified silica powder;

[0042] Polyvinyl chloride resin (PSLK1300 type), thermoplastic elastomer (TPE, i.e., synthetic rubber), dioctyl phthalate, calcium zinc stabilizer (commercially available, model CZX-683), silane coupling agent (commercially available, model KH-560) and processing aid (specifically ACR processing aid) were placed in an oven and dried at 50°C until the moisture content was less than 0.5 wt%.

[0043] S1.2 Add 80 parts of dried polyvinyl chloride resin, 25 parts of dried thermoplastic elastomer, 10 parts of dried dioctyl phthalate, 5 parts of dried calcium-zinc stabilizer, 5 parts of dried silane coupling agent modified silica, and 2 parts of dried processing aid into a high-speed mixer and mix at 1200 rpm for 10 min to obtain a mixture.

[0044] The mixture is fed into a twin-screw extruder for blending. The temperature of the first zone of the twin-screw extruder is 180℃, the temperature of the second zone is 185℃, and the temperature of the third zone is 190℃. The extruder spindle speed is 50 rpm. After cooling, pelletizing, and cooling, inner layer composite particles are obtained. The inner layer composite particles are extruded through a flat plate and cooled to obtain inner layer sheet.

[0045] S2. Mix 6 parts of barium 2-ethylhexanoate, 1 part of zinc ethylhexanoate, 15 parts of phosphite, 1 part of 2,6-ditert-butyl-p-cresol, 1 part of bisphenol A antioxidant (antioxidant 1010, Irganox 1010, purity ≥98%), 1 part of ultraviolet absorber (UV-531, 2-hydroxy-4-nonoxybenzophenone, purity ≥98%), and liquid paraffin (industrial grade white oil 32#, viscosity grade 68mm). 2 Mix 2 parts of / s) and 1 part of higher alcohol defoamer (octanol, analytical grade ≥99%, model C8-OH) to obtain a composite stabilizer;

[0046] 60 parts of polyvinyl chloride resin, 8 parts of azodicarbonyl foaming agent (AC foaming agent, industrial grade, model AC-7000), 30 parts of dioctyl phthalate, and 2 parts of composite stabilizer were mixed in a high-speed kneader for 10 minutes, and then placed in an injection molding machine. The injection nozzle temperature was set to 180℃, the front temperature to 185℃, and the middle and rear temperatures to 190℃; the melt temperature was set to 180℃, the mold temperature to 80℃, the injection pressure to 100 MPa, and the screw speed to 28 rpm, forming a PVC foam board with a fine pore structure, which is the outer layer.

[0047] S3. Mix ethylene-vinyl acetate copolymer (EVA) and peroxide crosslinking agent (DCP, i.e., dicumyl peroxide) at a mass ratio of 100:0.5 and stir until homogeneous to obtain an adhesive mixture;

[0048] A 2mm thick adhesive mixture is coated on the surface of both the inner and outer layers of the board. The inner and outer layers are then bonded together in a molten state using the adhesive mixture to obtain a composite board.

[0049] Example 2

[0050] S1.1 Disperse 5g of silica powder in 100mL of anhydrous ethanol and sonicate for 30min to obtain a uniform suspension; under stirring, add 2g of γ-aminopropyltriethoxysilane (KH-550) and adjust the pH of the solution to 5 (using glacial acetic acid); react in a 60℃ water bath for 3h to allow the coupling agent to fully react with the hydroxyl groups on the silica surface; after the reaction, filter the product under vacuum, wash it with anhydrous ethanol and deionized water until neutral, and then dry it under vacuum at 80℃ for 12h to obtain silane coupling agent modified silica powder;

[0051] Polyvinyl chloride resin (PSLK1300 type), thermoplastic elastomer (TPE, i.e., synthetic rubber), dioctyl phthalate, calcium zinc stabilizer (commercially available, model CZX-683), silane coupling agent (commercially available, model KH-560) and processing aid (specifically ACR processing aid) were placed in an oven and dried at 50°C until the moisture content was less than 0.5 wt%.

[0052] S1.2 Add 85 parts of dried polyvinyl chloride resin, 20 parts of dried thermoplastic elastomer, 12 parts of dried epoxidized soybean oil, 6 parts of dried lead salt stabilizer, 4 parts of dried silane coupling agent modified silica, and 2 parts of dried processing aid into a high-speed mixer and mix at 1200 rpm for 10 min to obtain a mixture.

[0053] The mixture is fed into a twin-screw extruder for blending. The temperature of the first zone of the twin-screw extruder is 180℃, the temperature of the second zone is 185℃, and the temperature of the third zone is 190℃. The extruder spindle speed is 50 rpm. After cooling, pelletizing, and cooling, inner layer composite particles are obtained. The inner layer composite particles are extruded through a flat plate and cooled to obtain inner layer sheet.

[0054] S2. 6 parts of barium 2-ethylhexanoate, 0.5 parts of zinc ethylhexanoate, 15 parts of phosphite, 0.5 parts of 2,6-ditert-butyl-p-cresol, 2 parts of bisphenol A antioxidant (antioxidant 1010, Irganox 1010, purity ≥98%), 3 parts of UV absorber UV-531 (2-hydroxy-4-nonoxybenzophenone, purity ≥98%), and liquid paraffin (industrial grade white oil 32#, viscosity grade 68mm). 2 A composite stabilizer is obtained by mixing 5 parts of / s) and 0.5 parts of higher alcohol defoamer (octanol, analytical grade ≥99%, model C8-OH).

[0055] 65 parts of polyvinyl chloride resin, 5 parts of azodicarbonyl foaming agent (AC foaming agent, industrial grade, model AC-7000), 25 parts of epoxidized soybean oil, and 5 parts of composite stabilizer were mixed in a high-speed kneader for 10 minutes, and then placed in an injection molding machine. The injection nozzle temperature, front temperature, and middle and rear temperature of the injection molding machine were set to 190℃, 195℃, and 195℃, respectively. The melt temperature was set to 200℃, the mold temperature was set to 90℃, the injection pressure was set to 100 MPa, and the screw speed was set to 28 rpm, forming a PVC foam board with a fine pore structure, which is the outer layer.

[0056] S3. Mix ethylene-vinyl acetate copolymer (EVA) and peroxide crosslinking agent (DCP, i.e., dicumyl peroxide) at a mass ratio of 100:1.0 and stir until homogeneous to obtain an adhesive mixture;

[0057] A 2mm thick adhesive mixture is coated on the surface of both the inner and outer layers of the board. The inner and outer layers are then bonded together in a molten state using the adhesive mixture to obtain a composite board.

[0058] Example 3

[0059] S1.1 Disperse 5g of silica powder in 100mL of anhydrous ethanol and sonicate for 30min to obtain a uniform suspension. Under stirring, add 2g of γ-aminopropyltriethoxysilane (KH-550) and adjust the pH of the solution to 4.5 (using glacial acetic acid). React in a 60℃ water bath for 3h to allow the coupling agent to fully react with the hydroxyl groups on the silica surface. After the reaction, filter the product under vacuum, wash it successively with anhydrous ethanol and deionized water until neutral, and then vacuum dry it at 80℃ for 12h to obtain silane coupling agent modified silica powder.

[0060] Polyvinyl chloride resin (PSLK1300 type), thermoplastic elastomer (TPE, i.e., synthetic rubber), dioctyl phthalate, calcium zinc stabilizer (commercially available, model CZX-683), silane coupling agent (commercially available, model KH-560) and processing aid (specifically ACR processing aid) were placed in an oven and dried at 50°C until the moisture content was less than 0.5 wt%.

[0061] S1.2 Add 90 parts of dried polyvinyl chloride resin, 15 parts of dried thermoplastic elastomer, 10 parts of dried epoxidized soybean oil, 5 parts of dried calcium-zinc stabilizer, 3 parts of dried silane coupling agent modified silica, and 1 part of dried processing aid into a high-speed mixer and mix at 1200 rpm for 10 min to obtain a mixture.

[0062] The mixture is fed into a twin-screw extruder for blending. The temperature of the first zone of the twin-screw extruder is 180℃, the temperature of the second zone is 185℃, and the temperature of the third zone is 190℃. The extruder spindle speed is 50 rpm. After cooling, pelletizing, and cooling, inner layer composite particles are obtained. The inner layer composite particles are then calendered and cooled to obtain inner layer sheets.

[0063] S2. 6.5 parts of barium 2-ethylhexanoate, 0.8 parts of zinc ethylhexanoate, 18 parts of phosphite, 2 parts of 2,6-ditert-butyl-p-cresol, 0.5 parts of bisphenol A antioxidant (antioxidant 1010, Irganox 1010, purity ≥98%), 1 part of UV absorber UV-531 (2-hydroxy-4-nonoxybenzophenone, purity ≥98%), and liquid paraffin (industrial grade white oil 32#, viscosity grade 68mm). 2 Mix 2 parts of / s) and 0.8 parts of higher alcohol defoamer (octanol, analytical grade ≥99%, model C8-OH) to obtain a composite stabilizer;

[0064] 70 parts of polyvinyl chloride resin, 5 parts of azodicarbonyl foaming agent (AC foaming agent, industrial grade, model AC-7000), 20 parts of epoxidized soybean oil, and 5 parts of composite stabilizer were mixed in a high-speed kneader for 10 minutes, and then placed in an injection molding machine. The injection nozzle temperature, front temperature, and middle and rear temperature of the injection molding machine were set to 185℃, 185℃, and 192℃, respectively. The melt temperature was set to 190℃, the mold temperature was set to 85℃, the injection pressure was set to 100 MPa, and the screw speed was set to 28 rpm, forming a PVC foam board with a fine pore structure, which is the outer layer.

[0065] S3. Mix ethylene-vinyl acetate copolymer (EVA) and peroxide crosslinking agent (DCP) at a mass ratio of 100:0.8, stir until homogeneous, and obtain an adhesive mixture;

[0066] A 2mm thick adhesive mixture was coated onto the surfaces of both the inner and outer layers of the composite board. The inner and outer layers were then bonded together in a molten state using the adhesive mixture to obtain a composite board. Electron microscopy was performed on the inner, middle, and outer layers of the composite board obtained in this embodiment. The results are as follows: Figure 2 As shown, a is the electron microscope image of the inner layer, b is the electron microscope image of the middle layer, and 3 is the electron microscope image of the outer layer.

[0067] Depend on Figure 2 It can be seen that the cross-section is dense, the interface is continuous, and the outer closed pores are uniform (average pore size 30–100 μm); this result shows that EVA crosslinking and modified SiO2 can synergistically improve interfacial bonding and energy dissipation capacity.

[0068] Example 4

[0069] The composite board was prepared in the same manner as in Example 3, except for the following conditions:

[0070] S3. A layer of ethylene-vinyl acetate copolymer (EVA) with a thickness of 2 mm is coated on the surface of the inner layer board and the surface of the outer layer board respectively. The inner layer board and the outer layer board are bonded together by the ethylene-vinyl acetate copolymer in the molten state to obtain a composite board.

[0071] In other words, no peroxide crosslinking agent (DCP) was added to the intermediate layer in this embodiment.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 3 is that no thermoplastic elastomer (TPE) was added to the inner layer.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 3 is that no foaming agent was added.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 3 is that no silane coupling agent was added to modify the silica.

[0078] Performance testing

[0079] The impact strength, tensile strength, elongation at break, and aging resistance of the composite panels prepared in Examples 1-4 and Comparative Examples 1-3 were tested (specifically, using the xenon arc lamp method at an irradiance of 0.51 W / m²). 2 The tensile strength loss rate after 240 h of ultraviolet irradiation under the cyclic conditions of @340nm, blackboard temperature 63±3℃, relative humidity 50±10%, water spraying for 18 min / light irradiation for 102 min is shown in Table 1.

[0080] The impact performance was tested in accordance with GB / T 1043.1-2008 Determination of impact performance of simply supported plastic beams Part 1 Non-instrumental impact test (without notches in the specimens);

[0081] Tensile strength was tested in accordance with GB / T 1040.2-2006 Determination of tensile properties of plastics - Part 2: General test methods for molded and extruded plastics;

[0082] The elongation at break was tested in accordance with GB / T 1040.2-2006 Determination of tensile properties of plastics Part 2: General test methods for molded and extruded plastics;

[0083] The aging resistance (tensile strength loss rate after ultraviolet irradiation) was tested in accordance with GB / T 16422.2-2022 Plastics Laboratory Light Source Exposure Test Method Part 2: Xenon Arc Lamp.

[0084] Table 1. Test results of impact strength, tensile strength, elongation at break, and tensile strength loss rate under ultraviolet irradiation.

[0085]

[0086] As shown in Table 1, the impact strength of the composite panels prepared in Examples 1-4 is ≥31.8 kJ / m. 2 Tensile strength ≥147MPa.

[0087] To verify the stability and interlayer adhesion of the composite panels under extreme low-temperature conditions, this application conducted low-temperature static storage, thermal cycling, and peel strength tests. The test methods and results are as follows:

[0088] Low-temperature static storage performance test: Each composite board sample was placed in a constant temperature freezer and stored at -50℃ for 7 days. After 7 days, it was taken out and restored to room temperature. The impact strength of each sample was tested again according to GB / T 1043.1-2008 Determination of impact properties of simply supported plastic beams Part 1 Non-instrumental impact test. The results are shown in Table 2. The strength change rate was calculated according to the formula: strength change rate = (impact strength after storage - initial impact strength) ÷ initial impact strength. The results are shown in Table 2.

[0089] Thermal cycling performance test: Each composite board sample was cycled 20 times between -50℃ and 20℃ (each temperature value lasted for 1 hour) to simulate the mechanical fatigue state under the temperature difference between day and night in winter. After cycling, the impact strength, tensile strength and elongation at break of each sample were tested again. The impact strength change rate was calculated according to the formula: Impact strength change rate = (impact strength after cycling - initial impact strength) ÷ initial impact strength. The tensile strength change rate was calculated according to the formula: Tensile strength change rate = (tensile strength after cycling - initial tensile strength) ÷ initial tensile strength. The elongation at break change rate was calculated according to the formula: Elongation at break = (elongation at break after cycling - initial elongation at break) ÷ initial elongation at break. The corresponding values ​​of each index obtained in Table 1 are the initial values ​​of each index. The results are shown in Table 3.

[0090] Peel strength test: The peel strength between the intermediate layer (EVA adhesive layer) and the inner and outer layers was tested using the 180° peel method, referring to GB / T 2790-1995 Adhesives 180° Peel Strength Test Method Flexible Materials vs. Rigid Materials. The results are shown in Table 4.

[0091] Table 2 Results of Low Temperature Impact Strength Test

[0092] Group <![CDATA[Initial impact strength (kJ / m 2 )]]> <![CDATA[Impact strength after 7 days (kJ / m 2 )]]> Intensity change rate (%) Example 1 32.0 30.5 -4.7 Example 2 33.0 31.8 -3.6 Example 3 32.5 31.0 -4.6 Example 4 31.8 29.5 -7.2 Comparative Example 1 25.5 19.0 -25.5 Comparative Example 2 27.0 23.8 -11.8 Comparative Example 3 26.5 23.3 -12.1

[0093] As shown in Table 2, the composite panels prepared in Examples 1-3 maintained high impact strength after being stored at ultra-low temperature (-50℃) for 7 days, without significant cracking or performance degradation. This result indicates that the composite panels of the present invention possess good reliability for long-term use at low temperatures.

[0094] Table 3. Test results of the rate of change of impact strength, tensile strength, and elongation at break after cycling.

[0095] Group Impact strength change rate, % Tensile strength change rate, % Change in elongation at break, % Example 1 -5.3 -3.0 -4.2 Example 2 -3.8 -2.5 -3.6 Example 3 -4.5 -2.8 -4.0 Example 4 -6.5 -4.0 -5.0 Comparative Example 1 -18.0 -10.0 -22.0 Comparative Example 2 -10.5 -6.5 -12.0 Comparative Example 3 -12.0 -7.5 -14.0

[0096] As shown in Table 3, the composite panels prepared in Examples 1-4 maintained high mechanical properties after thermal cycling tests, and no cracking or delamination was observed. This result indicates that the composite panels of the present invention have good structural stability and are suitable for applications in complex working conditions in cold regions.

[0097] Table 4. Peel strength test results

[0098] Group Inner layer-to-middle layer peel strength, N / cm Peel strength between intermediate and outer layers, N / cm Example 1 17.2 15.6 Example 2 18.0 16.2 Example 3 17.8 15.9 Example 4 15.5 14.0 Comparative Example 1 10.5 9.0 Comparative Example 2 12.0 10.5 Comparative Example 3 11.5 10.0

[0099] As shown in Table 4, the composite boards prepared in Examples 1-4 have good bonding between the middle layer and the outer and inner layers, and have excellent anti-delamination ability, which can provide structural protection for the long-term use of the product.

[0100] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A composite board, characterized in that, Along the direction from the inside out, the composite board sequentially includes an inner layer containing polyvinyl chloride resin and thermoplastic elastomer, an intermediate layer containing ethylene-vinyl acetate copolymer, and an outer layer containing polyvinyl chloride resin foam.

2. The composite board as described in claim 1, characterized in that, In the inner layer, the mass ratio of polyvinyl chloride resin to thermoplastic elastomer is 80-90:15-35.

3. The composite board as described in claim 1, characterized in that, The inner layer also includes a first plasticizer, a first stabilizer, modified silica, and processing aids.

4. The composite board as described in claim 3, characterized in that, The mass ratio of the first plasticizer to the thermoplastic elastomer is 5-15:15-35.

5. The composite board as described in claim 3, characterized in that, The modified silica is selected from silane coupling agent modified silica.

6. The composite board as described in claim 1, characterized in that, The intermediate layer also includes a peroxide crosslinking agent.

7. The composite board as described in claim 1, characterized in that, The outer layer also includes a foaming agent, a second plasticizer, and a second stabilizer.

8. The composite board as described in claim 7, characterized in that, The second stabilizer includes barium 2-ethylhexanoate, zinc ethylhexanoate, phosphite, 2,6-ditert-butyl-p-cresol, bisphenol A antioxidant, ultraviolet absorber, liquid paraffin, and alcohol defoamer.

9. The composite board as described in claim 8, characterized in that, By weight, the second stabilizer comprises 6-7 parts of barium 2-ethylhexanoate, 0.5-1 parts of zinc ethylhexanoate, 15-20 parts of phosphite, 0.5-2 parts of 2,6-di-tert-butyl-p-cresol, 0.5-2 parts of bisphenol A antioxidant, 1-3 parts of ultraviolet absorber, 2-5 parts of liquid paraffin, and 0.5-1 parts of alcohol defoamer.

10. The method for preparing the composite board according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Mix the polyvinyl chloride resin and the thermoplastic elastomer to obtain a mixture, melt-blend and extrude the mixture, cool and pelletize it to obtain inner layer composite particles; shape the inner layer composite particles by flat extrusion or calendering process, cool it to obtain inner layer sheet; S2. The polyvinyl chloride resin foam is injection molded to obtain the outer layer sheet; S3. The ethylene-vinyl acetate copolymer is coated on the surface of the inner layer sheet and the surface of the outer layer sheet respectively. The inner layer sheet and the outer layer sheet are bonded together by the ethylene-vinyl acetate copolymer in the molten state to obtain the composite sheet.

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