A composite material for fireproofing wood board based on chlorinated polyvinyl chloride and a method for preparing the same

Abstract

This invention relates to the field of building materials technology, specifically to a composite material for fire-resistant chlorinated polyvinyl chloride (PVC) wood panels and its preparation method. It comprises wood panels, chlorinated polyvinyl chloride resin, ceramic fibers, adhesives, nano-layered bimetallic hydroxide, zirconium phosphate, and maleic anhydride-grafted chlorinated polyvinyl chloride. In this composite material and its preparation method, functional components are combined with a wood matrix, and maleic anhydride-grafted chlorinated polyvinyl chloride is used as an interface compatibilizer to form a wood-fire-resistant functional layer-ceramic fiber reinforcement layer-fire-resistant functional layer laminated structure. This effectively isolates heat and oxygen, improving the fire resistance of the material. Simultaneously, the nano-layered bimetallic hydroxide and zirconium phosphate form a dense carbon layer under high temperature, effectively reducing the release of smoke and toxic gases, thereby improving the problems of flammability, rot, cracking, and peeling of the protective layer in traditional wood-based materials.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and more specifically, to a composite material for fire-resistant wood boards made of chlorinated polyvinyl chloride and its preparation method. Background Technology

[0002] Currently, wood-based composite materials are widely used in the construction industry due to their lightweight and environmentally friendly advantages. However, traditional wood suffers from problems such as flammability, rot, cracking, and insect infestation, limiting its application. Existing technologies improve the fire resistance and durability of wood by coating it with fire-retardant paint or impregnating it with flame retardants, but these methods still have the following shortcomings regarding the bonding strength between the wood and the protective layer and its long-term performance stability:

[0003] For example, the protective layer is prone to peeling and has poor water resistance. On the one hand, wood differs from most external protective materials in chemical properties and physical structure, resulting in poor interfacial compatibility. The bonding force mainly relies on weak physical adsorption rather than strong chemical bonding. On the other hand, traditional construction techniques cannot ensure that the protective material completely wets and deeply anchors the porous surface of the wood, and the resulting protective layer often has microscopic defects. Under repeated environmental stress (such as temperature and humidity changes, ultraviolet radiation) or usage loads, these weak points will deteriorate rapidly, causing the protective layer to crack, warp, and eventually peel off. At the same time, interfacial defects and the discontinuity of the protective layer itself make it easier for moisture, corrosive media, and microorganisms to penetrate and diffuse, resulting in a decrease in water resistance. This not only reduces the fireproof and corrosion-resistant effect of the material and increases maintenance costs, but also affects the service life of the material, thereby reducing the safety and reliability of wood-based composite materials in building applications.

[0004] Therefore, there is an urgent need for a composite material for fire-resistant wood boards made of chlorinated polyvinyl chloride and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a chlorinated polyvinyl chloride composite material and its preparation method that have excellent fire resistance, corrosion resistance, insect resistance and crack resistance, while retaining the lightweight, high strength and thermal insulation properties of wood, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, firstly, the present invention provides a composite material for chlorinated polyvinyl chloride fire-retardant wood boards, comprising the following raw materials:

[0007] 100 parts wood board; 20-40 parts chlorinated polyvinyl chloride resin; 5-15 parts ceramic fiber; 10-20 parts adhesive; 1-5 parts nano-layered bimetallic hydroxide; 3-8 parts zirconium phosphate; 5-10 parts maleic anhydride-grafted chlorinated polyvinyl chloride; wherein the adhesive is one of epoxy resin adhesive, polyurethane adhesive or ethylene-vinyl acetate copolymer hot melt adhesive.

[0008] The wood board body serves as the base material, and its surface is bonded with an adhesive to form a fire-resistant reinforcing layer composed of chlorinated polyvinyl chloride resin, ceramic fibers, nano-layered bimetallic hydroxide, and zirconium phosphate. The chlorinated polyvinyl chloride resin and ceramic fibers are interfacially bonded through maleic anhydride grafting onto chlorinated polyvinyl chloride, forming a continuous and dense flame-retardant and heat-insulating skeleton to isolate heat and oxygen. The nano-layered bimetallic hydroxide and zirconium phosphate decompose and release flame-retardant gases under high temperatures, promoting the formation of a char layer and effectively reducing the release of smoke and toxic gases. Simultaneously, they interweave with the ceramic fiber network, enhancing interlayer bonding and crack resistance. This not only improves fire resistance but also enhances the material's dimensional stability and durability.

[0009] Furthermore, the synergistic effect of the aforementioned nanolayered bimetallic hydroxide and zirconium phosphate mainly lies in the following: the nanolayered bimetallic hydroxide decomposes upon heating, releasing water and carbon dioxide, absorbing a large amount of heat and diluting combustible gases, while its layered structure forms a physical barrier in the condensed phase; zirconium phosphate decomposes upon heating to generate polyphosphoric acid and zirconium oxide. Polyphosphoric acid promotes the dehydration and carbonization of wood and polymer matrices, forming a dense and stable expanded carbon layer, while zirconium oxide acts as a high-temperature resistant skeleton to enhance the strength of the carbon layer; the synergistic effect of the two is manifested through the following chemical processes:

[0010] The decomposition of nanolayered bimetallic hydroxides is as follows: ;

[0011] The decomposition of zirconium phosphate (ZrP) is as follows: ;

[0012] Polyphosphoric acid further reacts with the matrix to promote char formation: ;

[0013] It effectively improves the limiting oxygen index of composite materials, reduces the heat release rate and total smoke release, thereby enhancing the fire safety level and smoke suppression capability of composite materials.

[0014] Secondly, according to Figure 1 As shown, the present invention provides a method for preparing a composite material for chlorinated polyvinyl chloride fire-retardant wood board, comprising the following steps:

[0015] S1. Pretreatment and activation of wood substrate: The wood board is placed in an electric heating drying oven and dried at 85℃±5℃ for 4-6 hours to achieve a moisture content of 8%-12%. Subsequently, the dried board is placed in the vacuum reaction chamber of a low-temperature plasma treatment device, and argon or oxygen is introduced as the treatment gas. The board is treated for 60-180 seconds at a power of 100-500W, a gas flow rate of 20-80sccm, and a vacuum degree of 10-50Pa. This process generates hydroxyl and carboxyl active groups on the wood surface and forms a micron-nano-scale rough structure, resulting in a pretreated wood substrate with high surface reactivity.

[0016] S2. Preparation of Composite Fire-Retardant Slurry: Chlorinated polyvinyl chloride resin, ceramic fiber, nano-layered bimetallic hydroxide, zirconium phosphate, and maleic anhydride-grafted chlorinated polyvinyl chloride are placed in a high-speed mixer and mixed for 8-15 minutes at 40-45℃ and 300-500 r / min to initially and uniformly disperse the materials, obtaining a premixed dry material. Subsequently, plasticizers and heat stabilizers are added to the premixed dry material, and it is transferred to an internal mixer and melt-blended for 15-25 minutes at 160-180℃ and 40-60 r / min to form a homogenized fire-retardant composite masterbatch. Finally, the fire-retardant... The composite masterbatch and adhesive are added together to a two-roll mill and blended and dispersed for 20-30 minutes under the conditions of a roll temperature of 80-100℃ and a rotation speed of 15-25r / min through mechanical shearing and melting to obtain a composite fire-retardant slurry with high viscosity and continuous film-forming ability. In this process, maleic anhydride-grafted chlorinated polyvinyl chloride is used as an interface modifier. The anhydride functional groups at the end of its molecular chain can form chemical bonds with polar groups such as hydroxyl groups on the surface of wood, and at the same time, it can undergo a coupling reaction with silanol groups on the surface of ceramic fibers, thereby constructing a stable molecular bridging structure between the organic polymer matrix and the inorganic reinforcing material.

[0017] S3. Multi-layer asynchronous composite: A composite fire-retardant slurry is uniformly applied to the surface of a pre-treated wood substrate via extrusion coating to form a fire-retardant layer with a thickness of 0.5-2.0 mm. Subsequently, ceramic fiber cloth is laid on the surface of the incompletely cured fire-retardant layer, and pre-pressed using hot rollers under a pressure of 0.5-1.5 MPa and a temperature of 90-120℃ to achieve initial bonding between the ceramic fiber cloth and the fire-retardant layer. Furthermore, to further increase the initial stability of the interlayer bonding, "U"-shaped nails or other high-temperature resistant metal fasteners are used for physical reinforcement at the edges or specific points of the pre-pressed board to prevent displacement of the ceramic fiber cloth during transport and subsequent processing. Specific locations include at least the overlap seams at the splicing of ceramic fiber cloth, the geometric center area of ​​the board, and the edges of openings or cuts reserved due to the structure. Other high-temperature resistant metal fasteners are metal connectors that can withstand the high-temperature environment (usually above 150°C) during hot pressing and cross-linking curing processes, including at least stainless steel or galvanized steel flat-head T-shaped nails, wavy clips, and ring pins. Next, a composite fire-retardant functional slurry is coated again on the surface of the ceramic fiber cloth to form a symmetrical coating structure, resulting in a multi-layer composite precursor with preliminary interlayer bonding. Then, an asynchronous hot-pressing composite is performed using a dual-belt press to obtain a composite board with a stable stacked structure of "wood-fire-retardant functional layer-ceramic fiber reinforcement layer-fire-retardant functional layer".

[0018] S4. Interface Crosslinking and Structural Curing: The composite board is placed in a high-pressure reactor and heated to 150-170℃ at a rate of 2-5℃ / min under nitrogen protection, while maintaining a pressure of 1-3MPa for 30-60 minutes. This allows the anhydride groups in maleic anhydride-grafted chlorinated polyvinyl chloride to undergo esterification or etherification reactions with the active groups on the wood surface and the silanol groups on the ceramic fiber surface, forming a three-dimensional crosslinking network. Subsequently, the temperature is lowered to below 80℃, and the board is removed after depressurization. This completes the interface chemical crosslinking and overall structural curing. The high-pressure thermal crosslinking reaction strengthens the organic-inorganic interface bond at the molecular scale, forming a stable "wood-polymer-ceramic fiber" ternary interpenetrating network. This improves the interlaminar shear strength and durability of the composite material, resulting in a fire-resistant wood board composite material with a stable three-dimensional crosslinking network.

[0019] S5. Post-treatment and functional enhancement: The fire-resistant wood board composite material is placed in an ultraviolet cross-linking device and irradiated with ultraviolet light at a wavelength of 254nm for 5-15 minutes to induce a photo-cross-linking reaction of the surface polymer molecular chains, forming a dense surface protective layer. Subsequently, a hydrophobic finishing agent is uniformly applied to the surface of the board by spraying, and then heat-treated at 120-140℃ for 20-40 minutes to allow the hydrophobic components to form a stable superhydrophobic film layer through chemical bonding with the material surface, ultimately obtaining a chlorinated polyvinyl chloride fire-resistant wood board composite material with durable fire resistance, corrosion resistance, insect resistance, crack resistance, and self-cleaning functions.

[0020] Furthermore, in S1, the wood board is made of solid wood or engineered wood, with a density of 0.35-0.75 g / cm³.

[0021] Furthermore, in S2, the plasticizer is either dioctyl phthalate or epoxidized soybean oil, and the amount added is 3%-8% of the mass of the premixed dry material; the heat stabilizer is either calcium zinc stabilizer or organotin stabilizer, and the amount added is 1%-3% of the mass of the premixed dry material.

[0022] Furthermore, according to Figure 2 As shown, in step S3, the asynchronous hot pressing composite process of the dual-belt press includes the following steps:

[0023] S3.1 Pre-curing and Melt Infiltration: The multilayer composite precursor is fed into a dual-belt press. In the initial stage, pre-curing is performed at a temperature of 110-130℃ and a pressure of 1.0-2.0MPa to allow the surface fire-retardant slurry to melt and flow, fully filling the gaps in the ceramic fiber cloth mesh. Then, the main curing stage is entered, where the temperature is increased to 140-160℃ and the pressure is increased to 2.5-4.0MPa, and maintained for 8-15 minutes to allow the fire-retardant layer to melt and infiltrate, forming a three-dimensional interpenetrating network structure with the ceramic fiber cloth, thus obtaining a composite preform with a preliminary coherent interface structure.

[0024] S3.2 Asynchronous Hot Pressing and Gradient Curing: The composite preform is transferred to an asynchronous hot pressing system. The upper functional surface of the composite preform facing the exterior of the building or the side with high heat load risk is hot-pressed at a temperature of 150-170℃ and a pressure of 3.0-4.5MPa. Simultaneously, the lower functional surface facing the interior of the building or the side with low heat load risk is hot-pressed at a temperature of 120-140℃ and a pressure of 1.5-2.5MPa. This asymmetric temperature-pressure field is maintained for 10-20 minutes. By constructing a differentiated thermodynamic environment, each functional layer completes curing and cross-linking according to a preset gradient. The upper functional surface forms a dense, highly cross-linked fire-resistant barrier, while the lower functional surface maintains a moderately flexible stress buffer layer. This effectively adjusts the internal stress caused by the mismatch of the thermal expansion coefficients of different materials, avoids the formation of interlayer peeling or cracking defects, and at the same time enhances the fire resistance of the material, making the overall density and dimensional stability of the multi-layer structure more robust.

[0025] Furthermore, in step S5, the hydrophobic finishing agent includes the following preparation steps:

[0026] Fluorinated silane coupling agent, nano silica and organic solvent are placed in a reaction vessel at a mass ratio of 3-5:1-2:10-15 and mechanically stirred at 200-400 r / min for 30-60 min at a temperature of 60-80℃ to obtain a uniformly dispersed hydrophobic finishing agent.

[0027] Preferably, the fluorinated silane coupling agent is one or more of perfluorooctyltriethoxysilane and tridecafluorooctyltriethoxysilane; the organic solvent is a mixture of anhydrous ethanol and isopropanol in a mass ratio of 2-3:1; the nano-silica has a particle size range of 20-50 nm and a specific surface area of ​​150-200 m² / g.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. In this composite material for fire-resistant wood board made of chlorinated polyvinyl chloride and its preparation method, functional components such as chlorinated polyvinyl chloride resin, ceramic fiber, nano-layered bimetallic hydroxide, and zirconium phosphate are combined with a wood matrix, and maleic anhydride-grafted chlorinated polyvinyl chloride is used as an interface compatibilizer to form a composite material with a wood-fire-resistant functional layer-ceramic fiber reinforcement layer-fire-resistant functional layer laminate structure. This not only effectively isolates heat and oxygen and improves the fire resistance of the material, but also forms a dense carbon layer at high temperature through the synergistic effect of nano-layered bimetallic hydroxide and zirconium phosphate, effectively reducing the release of smoke and toxic gases. This improves the problems of flammability, rot, cracking, and peeling of the protective layer of traditional wood-based materials, and enhances the safety and service life of the material in building applications.

[0030] 2. In this chlorinated polyvinyl chloride fireproof wood board composite material and its preparation method, asynchronous hot pressing and gradient curing are used to form a multi-layered composite system under asymmetric temperature-pressure field conditions. Through differentiated thermodynamic environments, the upper and lower functional surfaces form a gradient cross-linked structure. The upper functional surface forms a dense, highly cross-linked fire-resistant barrier, while the lower functional surface maintains a moderately flexible stress buffer layer. This not only effectively adjusts the internal stress caused by the mismatch of thermal expansion coefficients of different materials and reduces the generation of interlayer peeling or cracking defects, but also forms a stable superhydrophobic protective film through ultraviolet light cross-linking and treatment of the material surface with a hydrophobic finishing agent. This enables the material to simultaneously possess durable fire safety, crack resistance, and self-cleaning function, thereby improving the application range of wood-based composite materials in the construction field. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the preparation method of the chlorinated polyvinyl chloride fire-retardant wood board composite material of the present invention;

[0032] Figure 2 This is a flowchart of the asynchronous hot pressing composite process of the dual-belt press of the present invention;

[0033] Figure 3 This is a line graph of the limiting oxygen index of the present invention;

[0034] Figure 4 This is a line graph showing the smoke density levels of the present invention.

[0035] Figure 5 This is a line graph showing the 24-hour water absorption rate of the present invention. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] First, 100 parts of solid cedar wood boards with a density of 0.45 g / cm³ were selected as the wood board body. They were placed in an electric heating drying oven and dried at 85°C for 5 hours, with the moisture content controlled at 10%. Then, low-temperature plasma treatment was carried out. The treatment gas was argon, the power was 300W, the gas flow rate was 50 sccm, the vacuum degree was 30Pa, and the treatment time was 120 seconds to obtain the pretreated wood substrate.

[0039] Next, 25 parts of chlorinated polyvinyl chloride resin, 8 parts of ceramic fiber, 2 parts of nano-layered bimetallic hydroxide, 4 parts of zirconium phosphate, and 6 parts of maleic anhydride-grafted chlorinated polyvinyl chloride were added to a high-speed mixer and mixed at 42°C and 400 r / min for 10 min to obtain a premixed dry material. Dioctyl phthalate (5% of the mass of the premixed dry material) and calcium-zinc stabilizer (2% of the mass of the premixed dry material) were added to the premixed dry material, and then transferred to an internal mixer and melt-blended at 170°C and 50 r / min for 20 min to form a fire-retardant composite masterbatch. The masterbatch and 15 parts of ethylene-vinyl acetate copolymer hot melt adhesive were added to a two-roll mill and blended and dispersed at 90°C and 20 r / min for 25 min to obtain a composite fire-retardant functional slurry.

[0040] Then, the slurry is applied to the surface of the pretreated wood substrate by extrusion to form a fire-retardant functional layer with a thickness of 1.0 mm; ceramic fiber cloth is laid on the surface of the fire-retardant functional layer that has not been fully cured, and pre-pressed by hot press rollers at 1.0 MPa and 110°C; then, composite fire-retardant functional slurry is applied again to the surface of the ceramic fiber cloth to form a symmetrical coating structure, thus obtaining a multilayer composite precursor.

[0041] The precursor was fed into a dual-belt press for asynchronous hot-pressing composite: first, it was pre-cured at 120℃ and 1.5MPa to melt and fill the gaps in the fiber cloth; then, in the main curing stage, it was held at 150℃ and 3.0MPa for 10 minutes; next, asynchronous hot pressing was performed, with the upper functional surface hot-pressed at 160℃ and 3.5MPa, and the lower functional surface hot-pressed at 130℃ and 2.0MPa, held for 15 minutes, to obtain a composite board with a stable laminated structure;

[0042] Then, the composite board was placed in a high-pressure reactor and heated to 160°C at 3°C / min under a nitrogen atmosphere, and the pressure was maintained at 2MPa for 45min. After that, it was cooled to below 70°C and depressurized before being taken out.

[0043] Then, the board was irradiated under 254nm ultraviolet light for 10 minutes, and then a hydrophobic finishing agent (prepared by mixing perfluorooctyltriethoxysilane, nano-silica (particle size 30nm) and anhydrous ethanol / isopropanol mixed solvent (mass ratio 2.5:1) in a mass ratio of 4:1.5:12) was sprayed on, and then heat-treated at 130℃ for 30 minutes to obtain chlorinated polyvinyl chloride fireproof wood board composite material.

[0044] Example 2

[0045] The preparation method is basically the same as in Example 1, except for the amount of raw materials and some process parameters: the wood board body is 100 parts of plywood with a density of 0.55 g / cm³; the amount of chlorinated polyvinyl chloride resin is 35 parts; the amount of ceramic fiber is 12 parts; the amount of nano-layered bimetallic hydroxide is 4 parts; the amount of zirconium phosphate is 6 parts; the amount of maleic anhydride-grafted chlorinated polyvinyl chloride is 8 parts; the adhesive is epoxy resin, with an amount of 18 parts; the plasticizer is epoxidized soybean oil, with an addition amount of 7% of the mass of the premixed dry material; the heat stabilizer is organotin stabilizer, with an addition amount of 1.5% of the mass of the premixed dry material; the two-roll open milling blending temperature is 95℃; in the asynchronous hot pressing composite, the hot pressing temperature of the upper functional surface is 165℃ and the pressure is 4.0 MPa, and the hot pressing temperature of the lower functional surface is 135℃ and the pressure is 2.2 MPa, held for 12 min; the interface crosslinking curing conditions are programmed temperature rise to 155℃, pressure 2.5 MPa, and treatment for 50 min.

[0046] Example 3

[0047] The preparation method is basically the same as in Example 1, except for the amount of raw materials and some process parameters: the wood board body is 100 parts of pine solid wood board with a density of 0.38 g / cm³; the amount of chlorinated polyvinyl chloride resin is 20 parts; the amount of ceramic fiber is 5 parts; the amount of nano-layered bimetallic hydroxide is 1 part; the amount of zirconium phosphate is 3 parts; the amount of maleic anhydride-grafted chlorinated polyvinyl chloride is 5 parts; the adhesive used is polyurethane adhesive, with an amount of 10 parts; and the plasticizer used is phthalic acid. Dioctyl ester was added at 3% of the mass of the premixed dry material; calcium-zinc stabilizer was used as the heat stabilizer, and its addition amount was 1% of the mass of the premixed dry material; the two-roll open mill blending temperature was 85℃; in the asynchronous hot pressing composite, the upper functional surface was hot-pressed at 155℃ and 3.0MPa, and the lower functional surface was hot-pressed at 125℃ and 1.8MPa, held for 18min; the interface crosslinking curing conditions were programmed temperature rise to 150℃, pressure 1.5MPa, and treatment for 60min.

[0048] Example 4

[0049] The preparation method is basically the same as in Example 1, except for the amount of raw materials and some process parameters: the wood board body is 100 parts of oriented strand board with a density of 0.70 g / cm³; the amount of chlorinated polyvinyl chloride resin is 40 parts; the amount of ceramic fiber is 15 parts; the amount of nano-layered bimetallic hydroxide is 5 parts; the amount of zirconium phosphate is 8 parts; the amount of maleic anhydride-grafted chlorinated polyvinyl chloride is 10 parts; the adhesive is ethylene-vinyl acetate copolymer hot melt adhesive, with an amount of 20 parts; the plasticizer is... Epoxidized soybean oil was added at 8% of the mass of the premixed dry material; organotin stabilizer was used as the heat stabilizer, and its addition amount was 3% of the mass of the premixed dry material; the two-roll open mill blending temperature was 100℃; in the asynchronous hot pressing composite, the upper functional surface was hot-pressed at 170℃ and 4.5MPa, and the lower functional surface was hot-pressed at 140℃ and 2.5MPa, held for 10min; the interface crosslinking curing conditions were programmed temperature rise to 170℃, pressure 3.0MPa, and treatment for 30min.

[0050] To verify that the chlorinated polyvinyl chloride fire-resistant wood board composite material prepared in the embodiments of the present invention has good fire safety and structural durability, the following test examples are used to illustrate the chlorinated polyvinyl chloride fire-resistant wood board composite material provided in the embodiments of the present invention.

[0051] Test case

[0052] The purpose of this experimental group is to investigate the effects of different component ratios on chlorinated polyvinyl chloride fireproof wood board composite materials, and to test the fire safety, mechanical properties and weather resistance of the composite materials of this invention. Specific test indicators include: limiting oxygen index, peak heat release rate, smoke density rating, interlaminar shear strength and water absorption rate.

[0053] Experimental Objective: Experimental groups A, B, C, and D adopted the component ratios of the chlorinated polyvinyl chloride fire-retardant wood board composite materials provided in Examples 1-4, respectively; the control group consisted of control groups A, B, C, D, E, F, G, and H, wherein:

[0054] Control group A

[0055] 100 parts of solid cedar wood boards with a density of 0.45 g / cm³ were selected and placed in an electric heating drying oven at 85°C for 5 hours to dry the wood boards while controlling the moisture content to 10%.

[0056] Control group B

[0057] Select 100 parts of solid cedar wood boards with a density of 0.45 g / cm³, dry them to a moisture content of 10%, and then directly apply commercially available intumescent fire retardant coating to their surface. The coating thickness is about 0.5 mm, and the coating is cured at room temperature for 24 hours.

[0058] Control group C

[0059] Select 100 parts of solid cedar wood boards with a density of 0.45 g / cm³, dry them to a moisture content of 10%, coat them with epoxy resin adhesive (15 parts), then attach ceramic fiber cloth, compact them, and cure them at room temperature.

[0060] Control group D

[0061] The preparation method and materials are the same as in Example 1, but nano-layered bimetallic hydroxide and zirconium phosphate were not added in the preparation of the composite fire-retardant functional slurry.

[0062] Control group E

[0063] The preparation method and materials are the same as in Example 1, but the steps of ultraviolet crosslinking and hydrophobic finishing agent spraying are omitted.

[0064] control group F

[0065] The preparation method and materials are the same as in Example 1, but instead of using a high-pressure reactor for thermal crosslinking during the interface crosslinking and structural curing process, the composite board is heat-treated at atmospheric pressure and 100°C for 60 minutes.

[0066] control group G

[0067] The preparation method and materials are the same as in Example 1. However, in the multilayer composite process, the laying of ceramic fiber cloth and the corresponding pre-pressing steps are omitted. Only a layer of composite fire-retardant functional slurry (about 1.0 mm thick) is coated on the surface of the wood substrate and then hot-pressed and cured. The remaining steps and parameters are the same as in Example 1.

[0068] control group H

[0069] The preparation method and materials are the same as in Example 1, but in the preparation method, the dual-belt press adopts synchronous hot pressing composite instead of asynchronous hot pressing composite. The specific steps are as follows: the multilayer composite precursor is fed into the dual-belt press and synchronously hot-pressed for 15 minutes at a temperature of 150°C and a pressure of 3.0MPa.

[0070] Test methods: The limiting oxygen index, peak heat release rate, smoke density grade, interlaminar shear strength, and water absorption rate of the composite material according to the present invention were tested respectively. The specific test methods are as follows:

[0071] Limiting Oxygen Index (LOI) Test: According to GB / T2406.2-2009 standard, the test was conducted using an HC-900C oxygen index meter. The sample was processed into standard dimensions (80mm×10mm×4mm) and vertically fixed in the combustion chamber. Under the conditions of 23±2℃ and 50±5%RH, the oxygen / nitrogen mixed flow rate was adjusted to 40±2mm / s. The top ignition method was used to determine the minimum oxygen concentration required for the sample to burn continuously for 3 minutes or for the burning length to reach 50mm. The oxygen index calculation formula is: LOI=[O2] / ([O2]+[N2])×100%, where [O2] and [N2] represent the flow rates of oxygen and nitrogen, respectively.

[0072] Peak heat release rate test: According to ISO5660-1:2015 standard, the test was conducted using an FTT0007 cone calorimeter. The sample (100mm×100mm×actual thickness) was placed horizontally and ignited under a radiation power of 50kW / m². The heat release rate was continuously measured based on the oxygen consumption principle. The peak heat release rate (pkHRR) within 180s after the start of the test was recorded. The calculation formula is based on the Huggett relation: HRR=E×Δ[O2]×A, where E is the oxygen consumption coefficient (taken as 13.1MJ / kg), Δ[O2] is the oxygen concentration difference, and A is the exposed area of ​​the sample.

[0073] Smoke density rating test: According to GB / T8627-2007 standard, the JCM-2 smoke density tester was used for measurement; the sample (75mm×75mm×actual thickness) was placed in a sealed smoke chamber, and propane fuel was used as the ignition source. The sample was exposed to flame conditions at 25±5℃ for 10 minutes. The change in smoke transmittance was recorded by the optical measurement system. The smoke density rating was calculated according to the formula SDC=(As / At)×100%, where As is the sample integral specific optical density and At is the theoretical maximum specific optical density.

[0074] Interlaminar shear strength test: According to GB / T20241-2006 standard, the test was conducted using a UTM5105 electronic universal testing machine. The specimen was processed into the specified size (50mm×20mm×actual thickness). A three-point bending fixture was used with a span of 5 times the specimen thickness and a loading speed of 2mm / min. The maximum load at interlaminar failure was recorded. The interlaminar shear strength was calculated using the formula τ=3F / (4b·h), where F is the failure load, b is the specimen width, and h is the specimen thickness.

[0075] Water absorption test: According to GB / T17657-2013 standard, the sample (50mm×50mm×actual thickness) was dried to constant weight at 50±2℃ and the initial mass (m0) was weighed. Then it was immersed in distilled water at 23±2℃ for 24h. After removing it and wiping off the surface moisture, the saturated mass (m1) was weighed immediately. The water absorption rate was calculated according to the formula W=(m1-m0) / m0×100%. The arithmetic mean of 5 parallel samples in each group of tests was taken.

[0076] Specific testing indicators are shown in Table 1.

[0077]

[0078] according to Figures 3-5 As shown in Table 1, the summary of the above comparative data is as follows:

[0079] In terms of fire safety, the limiting oxygen index of experimental group AD was higher than 34%, the peak heat release rate was lower than 100 kW / m², and the smoke density was lower than 55%, demonstrating good flame retardant and smoke suppression performance. In contrast, the limiting oxygen index of control group A (pure wood) was only 18.2%, the peak heat release rate was as high as 285.6 kW / m², and the smoke density was 86.5%, indicating that untreated wood is flammable and produces a large amount of smoke. Although the performance of control groups B (coated with fire-retardant paint) and control group C (only ceramic fiber cloth was pasted) was improved, there was still a significant gap compared with the experimental group. In particular, the limiting oxygen index of control group D (without nano-layered bimetallic hydroxide and zirconium phosphate) was 30.1%, the peak heat release rate was 118.6 kW / m², and the smoke density was 68.3%, and its flame retardant and smoke suppression effects were significantly lower than those of the experimental group. This confirms the importance of the synergistic effect of nano-layered bimetallic hydroxide and zirconium phosphate in improving the fire safety level of materials.

[0080] In terms of mechanical properties, the interlaminar shear strength of experimental group AD ranged from 7.9 MPa to 9.8 MPa, demonstrating good interlaminar bonding strength. The interlaminar shear strength of control group C (only ceramic fiber cloth was bonded) was 5.1 MPa, while the values ​​of control group F (atmospheric pressure heat treatment) and control group G (ceramic fiber cloth omitted) were 6.8 MPa and 5.9 MPa, respectively, both lower than those of the experimental group. These data indicate that the high-pressure interfacial crosslinking reaction, the reinforcing effect of ceramic fiber cloth, and the asynchronous hot pressing process jointly promoted the formation of a three-dimensional crosslinked network, thereby improving the interlaminar bonding strength of the composite material.

[0081] In terms of weather resistance, the 24-hour water absorption rate of experimental group AD was less than 6.5%, indicating good waterproof performance. The water absorption rate of control group A (pure wood) was as high as 42.3%, while the water absorption rates of control group B (coated with fire-retardant paint) and control group C (only ceramic fiber cloth was pasted) were 35.6% and 28.4%, respectively. Although there was some improvement, it was still not ideal. The water absorption rate of control group E (without UV crosslinking and hydrophobic treatment) was 15.2%, which was higher than that of the experimental group. This proves that UV crosslinking and hydrophobic finishing agent treatment can form a stable superhydrophobic film layer and reduce the water absorption of the material.

[0082] Furthermore, the interlaminar shear strength of control group H (using synchronous hot pressing) was 7.1 MPa, lower than that of experimental group A (8.7 MPa); its peak heat release rate was 96.8 kW / m², higher than that of experimental group A (89.3 kW / m²). These data indicate that, compared with synchronous hot pressing, asynchronous hot pressing, by constructing an asymmetric temperature-pressure field, enables the upper and lower functional surfaces to form a gradient cross-linked structure, which helps to regulate the internal stress caused by the mismatch of thermal expansion coefficients of different materials, thereby improving the interlaminar bonding strength while maintaining the material's refractory properties.

[0083] In summary, the composite material preparation method provided by this invention uses maleic anhydride-grafted chlorinated polyvinyl chloride as an interface modifier, which promotes molecular bridging between the organic and inorganic phases; through the synergistic effect of nano-layered bimetallic hydroxide and zirconium phosphate, a dense carbon layer is formed at high temperature; and asynchronous hot pressing and gradient curing processes are used to form a structure with differentiated functions on the top and bottom surfaces; further ultraviolet crosslinking and hydrophobic treatment on the surface form a dense protective layer on the material surface, which not only improves the fire safety level and interlayer bonding strength of the composite material, but also improves the water resistance and dimensional stability of the material, thereby enhancing the comprehensive performance of wood-based composite materials in building applications.

[0084] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a composite material for fire-retardant wood boards made of chlorinated polyvinyl chloride, characterized in that, Includes the following steps: S1. Place the wood board in an electric heating drying oven for pretreatment and activation to form a pretreated wood substrate. S2. Chlorinated polyvinyl chloride resin, ceramic fiber, nano-layered bimetallic hydroxide, zirconium phosphate, and maleic anhydride-grafted chlorinated polyvinyl chloride are mixed in a high-speed mixer to form a premixed dry material. Plasticizer and heat stabilizer are added, and the mixture is transferred to an internal mixer for melt blending to form a fire-retardant composite masterbatch. Subsequently, the masterbatch is added to a two-roll mill for blending and dispersion with an adhesive to obtain a composite fire-retardant functional slurry. S3. Extrusion coating, ceramic fiber cloth laying and secondary coating are performed sequentially on the pretreated wood substrate to form a symmetrically coated multilayer composite precursor; then, asynchronous hot pressing composite is performed under asymmetrical temperature and pressure field conditions using a dual-belt press to obtain a composite board with a stable stacked structure of "wood-fireproof functional layer-ceramic fiber reinforcement layer-fireproof functional layer". S4. Place the composite board in a high-pressure reactor for hot pressing, then cool and depressurize it before taking out the board to obtain fireproof wood board composite material. S5. The fire-resistant wood board composite material is placed in an ultraviolet cross-linking device for irradiation treatment to form a dense surface protective layer; then a hydrophobic finishing agent is sprayed and heat-treated to obtain chlorinated polyvinyl chloride fire-resistant wood board composite material. In step S3, the asynchronous hot pressing composite process of the dual-belt press includes the following steps: S3.

1. The multi-layer composite precursor is fed into a dual-belt press. In the initial stage, a pre-curing treatment is performed at a temperature of 110-130℃ and a pressure of 1.0-2.0MPa to allow the surface fireproof slurry to melt and flow and fully fill the gaps in the ceramic fiber cloth mesh. Then, the main curing stage begins, where the temperature is increased to 140-160℃ and the pressure is increased to 2.5-4.0MPa, and held for 8-15 minutes to allow the fireproof functional layer to melt and penetrate, forming a three-dimensional interpenetrating network structure with the ceramic fiber cloth, thus obtaining a composite green body. S3.2 Transfer the composite blank to the asynchronous hot pressing system. The hot pressing temperature of the upper functional surface of the composite blank facing the outside of the building or the side with high heat load risk is 150-170℃ and the pressure is 3.0-4.5MPa. At the same time, the hot pressing temperature of the lower functional surface facing the inside of the building or the side with low heat load risk is 120-140℃ and the pressure is 1.5-2.5MPa. Maintain this asymmetric temperature-pressure field for 10-20 minutes. In step S4, the high-pressure reactor, under nitrogen protection, is programmed to heat to 150-170°C at a rate of 2-5°C / min, and the composite material is treated with a pressure of 1-3MPa for 30-60 minutes.

2. The method for preparing the composite material for fire-retardant wood board according to claim 1, characterized in that, In step S1, the pretreatment and activation of wood panels by the electric heating forced-air drying oven includes the following steps: The wood board is dried in an electric heating drying oven at 85℃±5℃ for 4-6 hours until its moisture content is 8%-12%. Then, it is transferred to the vacuum reaction chamber of a low-temperature plasma treatment device, where argon or oxygen is introduced as the treatment gas. The wood is treated for 60-180 seconds at a power of 100-500W, a gas flow rate of 20-80sccm, and a vacuum degree of 10-50Pa. This process generates hydroxyl and carboxyl active groups on the surface of the wood and forms a micron-nano-scale rough structure. The wood board is made of solid wood or engineered wood, with a density of 0.35-0.75 g / cm³.

3. The method for preparing the composite material for fire-retardant wood board according to claim 1, characterized in that, In S2, the plasticizer is either dioctyl phthalate or epoxidized soybean oil, and the amount added is 3%-8% of the mass of the premixed dry material; the heat stabilizer is either calcium zinc stabilizer or organotin stabilizer, and the amount added is 1%-3% of the mass of the premixed dry material.

4. The method for preparing the composite material for fire-retardant wood board according to claim 1, characterized in that, The adhesive is one of epoxy resin adhesive, polyurethane adhesive, or ethylene-vinyl acetate copolymer hot melt adhesive.

5. The method for preparing the composite material for fire-retardant wood board according to claim 1, characterized in that, In step S2, the high-speed mixer mixes for 8-15 minutes at a temperature of 40-45℃ and a speed of 300-500 r / min; the internal mixer melts and blends for 15-25 minutes at a temperature of 160-180℃ and a speed of 40-60 r / min; and the two-roll mill blends and disperses for 20-30 minutes at a roll temperature of 80-100℃ and a speed of 15-25 r / min through mechanical shearing and melting.

6. The method for preparing the composite material for fire-retardant wood board according to claim 1, characterized in that, In step S5, the hydrophobic finishing agent includes the following preparation steps: Fluorinated silane coupling agent, nano-silica and organic solvent are placed in a reaction vessel at a mass ratio of 3-5:1-2:10-15 and mechanically stirred at 200-400 r / min for 30-60 min at a temperature of 60-80℃ to obtain a hydrophobic finishing agent.

7. The method for preparing the composite material for fire-retardant wood board according to claim 6, characterized in that, The fluorinated silane coupling agent is one or more of perfluorooctyltriethoxysilane and tridecafluorooctyltriethoxysilane; the organic solvent is a mixture of anhydrous ethanol and isopropanol in a mass ratio of 2-3:1; the nano-silica has a particle size range of 20-50 nm and a specific surface area of ​​150-200 m² / g.

8. A chlorinated polyvinyl chloride fire-resistant wood board composite material prepared by the method for preparing chlorinated polyvinyl chloride fire-resistant wood board according to any one of claims 1-7, characterized in that, Including the following raw materials: 100 parts wood board; 20-40 parts chlorinated polyvinyl chloride resin; 5-15 parts ceramic fiber; 10-20 parts adhesive; 1-5 parts of nano-layered bimetallic hydroxide; 3-8 parts of zirconium phosphate; 5-10 parts of maleic anhydride-grafted chlorinated polyvinyl chloride.

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