High-strength flame-retardant lightweight wood-plastic composite material and preparation method thereof

Abstract

The invention discloses a high-strength flame-retardant lightweight wood-plastic composite material and a preparation method thereof. The composite material is prepared from the following components in parts by weight: 40-70 parts of PVC (polyvinyl chloride), 0-15 parts of calcium powder, 20-55 parts of a wood powder-based flame retardant, 1-5 parts of zinc hydroxystannate, 3-10 parts of a stabilizer, 0.3-1 part of PE (polyethylene) wax, 0.3-1 part of a high-temperature internal lubricant G60 and 4.5-8.5 parts of a flexibilizer HL100. The UL-94 flame retardant grade of the wood-plastic composite material can reach V-0 grade, the bending strength can reach 30-60 MPa, the tensile strength can reach 35-70 MPa, the density can reach 0.8-1.0 g / cm < 3 >, and the wood-plastic composite material has the advantages of simple process, environmental protection and wide application prospect, and is suitable for the fields of building templates, outdoor floors, fireproof doors and windows and the like with high requirements on mechanical properties and fireproof safety.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a high-strength, flame-retardant, lightweight wood-plastic composite material and its preparation method, applicable to fields with high requirements for mechanical properties and fire safety, such as building formwork, outdoor flooring, and fireproof doors and windows. Background Technology

[0002] Wood-plastic composites are a new type of material made by combining wood fibers with a plastic matrix through a specific process. They combine the advantages of both wood and plastic, exhibiting good processing performance, weather resistance, and recyclability. However, traditional wood-plastic composites still have some shortcomings in practical applications.

[0003] On the one hand, its strength often falls short of requirements for certain applications demanding high mechanical properties, such as structural components in buildings or parts subjected to heavy loads. On the other hand, since wood fibers and plastics are mostly flammable, wood-plastic composites have poor flame retardant properties, making them prone to combustion and spread in the event of a fire, increasing safety hazards. Furthermore, with the increasing demand for lightweight materials, the relatively high density of traditional wood-plastic composites also limits their application in weight-sensitive fields.

[0004] Currently, existing technology CN 106977844 A discloses an environmentally friendly, flame-retardant PVC wood-plastic composite material, which contains 20-50 parts of modified wood flour (obtained by blending wood flour and maleic anhydride-grafted polyethylene at elevated temperatures). This composite material exhibits good flame-retardant and mechanical properties. While this invention utilizes modified wood flour to achieve a wood-plastic composite material with good flame retardancy and mechanical properties, it does not explicitly measure the lightweight nature of the composite material. Furthermore, the function of the modified wood flour in the composite material is relatively singular; the modified wood flour only serves to increase interfacial compatibility. In addition, although some technologies on the market improve the strength, flame retardancy, or lightweight of wood-plastic composites, wood-plastic composites that simultaneously achieve high strength, flame retardancy, and lightweight properties are still relatively scarce. Some methods to increase strength may lead to increased material density, while adding flame retardants may reduce the material's mechanical properties, making it difficult to achieve an ideal balance among multiple performance indicators. Therefore, developing a wood-plastic composite material that simultaneously possesses high strength, good flame retardancy, and lightweight characteristics has significant practical implications. Summary of the Invention

[0005] Based on the above research background, this invention discloses a high-strength flame-retardant lightweight wood-plastic composite material and its preparation method. The high-strength flame-retardant lightweight wood-plastic composite material is prepared by using wood powder-based flame retardants, zinc hydroxystannate and calcium powder to achieve multi-effect synergy.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention is a high-strength, flame-retardant, lightweight wood-plastic composite material, composed of the following different components:

[0008] PVC 40-70 parts

[0009] Calcium powder 0-15 parts

[0010] 20-55 parts of wood powder-based flame retardant

[0011] 1-5 parts of zinc hydroxystannate

[0012] stabilizer 3-10 parts

[0013] PE wax 0.3-1 part

[0014] High-temperature internal lubricant (G60) 0.3-1 part

[0015] Toughening agent (HL100) 4.5-8.5 parts.

[0016] One of the functions of the aforementioned wood powder-based flame retardant is to synergistically enhance the flame retardant and smoke-suppressing properties with zinc hydroxystannate and calcium powder. Another function is to reduce the density of wood-plastic composites, making them lighter.

[0017] The aforementioned wood flour-based flame retardants can be modified wood fibers, bamboo fibers, rice husk powder, etc. Wood flour-based flame retardants are modified by multiple flame retardant elements to simultaneously improve the thermal stability, flame retardancy, and interfacial compatibility of wood flour.

[0018] Furthermore, the aforementioned zinc hydroxystannate is a flame retardant and smoke suppressant for wood-plastic composite materials, the high-temperature internal lubricant is G60, and the toughening agent is HL100.

[0019] This invention discloses a method for preparing a high-strength, flame-retardant, lightweight wood-plastic composite material. The method involves preparing the composite material by two melt blending processes using PVC, wood powder-based flame retardant, zinc hydroxystannate, stabilizer, PE wax, high-temperature internal lubricant, and toughening agent according to the stated component ratios. The melting temperature is 165-175 °C. The preparation process of the wood powder-based flame retardant is as follows:

[0020] (1) To carry out the boronization reaction of wood flour, the wood flour is dispersed in an aqueous solution of sodium tetraborate decahydrate (Na2B4O7•10H2O), the pH is adjusted to 10, so that the boron element is modified and grafted onto the surface of the wood flour, and then dried. The boronized powder obtained is denoted as BF.

[0021] (2) BF is placed in a certain chitosan solution. Through electrostatic action, chitosan is adsorbed onto the surface of BF and then dried. The resulting wood powder is called BNF.

[0022] (3) BNF is placed in a certain phytic acid solution. Through electrostatic action, phytic acid is adsorbed onto the surface of BNF and then dried. The resulting wood powder is called BNPF.

[0023] (4) In the same steps as above, Si elements are synergistically attached to the surface of wood flour BNPF through silane coupling agent to form wood flour BNP-Si-F modified with multiple flame retardant elements.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) This invention utilizes the synergistic effect of multiple components such as wood powder-based flame retardant, zinc hydroxystannate, and calcium powder to achieve an effective combination of high-strength flame retardancy and lightweighting, thus making a breakthrough in the field of wood-plastic composite materials. The introduction of wood powder-based flame retardant not only improves the flame retardant and smoke-suppressing performance of the material and effectively reduces the risk of fire, but also reduces the overall weight of the wood-plastic composite material, achieving lightweight design.

[0026] (2) This invention significantly enhances the mechanical properties of wood-plastic composites while ensuring flame retardant performance. By adjusting the component ratio and using wood powder-based flame retardants, the strength and durability of the material are enhanced. This comprehensive performance improvement enables the wood-plastic composites of this invention to be suitable for more and more demanding application scenarios, such as building formwork, outdoor flooring, fireproof doors and windows, and other fields with high load or high safety requirements.

[0027] (3) This invention employs a highly efficient flame-retardant system, with zinc hydroxystannate acting as a flame-retardant and smoke-suppressing agent. This, in conjunction with wood flour-based flame retardants and calcium powder, exerts multiple flame-retardant effects, thereby significantly improving the flame-retardant performance of the material. The wood-plastic composite material of this invention can effectively suppress flame spread, reduce smoke emissions, meet fire safety requirements, and improve the safety of the application environment.

[0028] (4) The preparation method of the present invention is simple and easy to implement, with high production efficiency and readily available raw materials. The preparation process of wood flour-based flame retardant improves the comprehensive performance of wood flour through multi-step synergistic modification. The steps are controllable, the equipment requirements are not high, which is conducive to large-scale industrial production, reduces production costs, and promotes the widespread application of high-strength flame-retardant wood-plastic composite materials.

[0029] (5) The wood powder (or wood fiber, bamboo fiber, rice husk powder, etc.) used in this invention is a renewable resource, and some components can be recycled and reused, which reflects the environmentally friendly commitment of this invention, conforms to the concept of sustainable development, reduces dependence on traditional petrochemical resources, and has significant social and economic benefits. Attached Figure Description

[0030] Figure 1 These are the UL-94 vertical burning test results of Examples 1-4 of the present invention. Detailed Implementation

[0031] Example 1:

[0032] BNP-Si-F wood flour-based flame retardant was prepared according to the method described in the patent. First melt blending: PVC (60 parts), wood flour-based flame retardant (20 parts), zinc hydroxystannate (3 parts), stabilizer (4.8 parts), PE wax (0.35 parts), high-temperature internal lubricant (G60, 0.4 parts), and toughening agent (HL100, 5.5 parts) were thoroughly mixed in a high-speed mixer. The mixture was then fed into a twin-screw extruder for a first melt blend at 170 °C, and extruded to obtain a preliminary batch of composite material. Second melt blending: The preliminary batch of composite material was crushed and premixed with calcium powder (15 parts) in a high-speed mixer. This mixture was then fed into another twin-screw extruder for a second melt blend at 170 °C, and hot-pressed at 170 °C to obtain the final product.

[0033] The wood-plastic composite material prepared in this embodiment has a flexural strength of up to 30 MPa, a tensile strength of up to 35 MPa, a flame retardant performance of UL-94 V0 level, and a density of approximately 1.0 g / cm³.

[0034] Example 2:

[0035] BNP-Si-F wood flour-based flame retardant was prepared according to the method described in the patent. First melt blending: PVC (55 parts), wood flour-based flame retardant (35 parts), zinc hydroxystannate (4 parts), stabilizer (5 parts), PE wax (0.3 parts), high-temperature internal lubricant (G60, 0.4 parts), and toughening agent (HL100, 6.0 parts) were thoroughly mixed in a high-speed mixer. The mixture was then fed into a twin-screw extruder for a first melt blend at 175 °C, and extruded to obtain a preliminary batch of composite material. Second melt blending: The preliminary batch of composite material was crushed and premixed with calcium powder (10 parts) in a high-speed mixer. This mixture was then fed into another twin-screw extruder for a second melt blend at 175 °C, and hot-pressed at 175 °C to obtain the final product.

[0036] The wood-plastic composite material prepared in this embodiment has a flexural strength of up to 50 MPa, a tensile strength of up to 60 MPa, a flame retardant performance of UL-94 V0 level, and a density of approximately 0.9 g / cm³.

[0037] Example 3:

[0038] BNP-Si-F wood flour-based flame retardant was prepared according to the method described in the patent. First melt blending: PVC (55 parts), wood flour-based flame retardant (40 parts), zinc hydroxystannate (5 parts), stabilizer (5 parts), PE wax (0.3 parts), high-temperature internal lubricant (G60, 0.4 parts), and toughening agent (HL100, 4.5 parts) were thoroughly mixed in a high-speed mixer. The mixture was then fed into a twin-screw extruder for a first melt blend at 165 °C, and extruded to obtain a preliminary batch of composite material. Second melt blending: The preliminary batch of composite material was crushed and premixed with calcium powder (5 parts) in a high-speed mixer. This mixture was then fed into another twin-screw extruder for a second melt blend at 175 °C, and hot-pressed at 165 °C to obtain the final product.

[0039] The wood-plastic composite material prepared in this embodiment has a flexural strength of up to 60 MPa, a tensile strength of up to 70 MPa, a flame retardant performance of UL-94 V0 level, and a density of approximately 0.8 g / cm³.

[0040] Example 4:

[0041] BNP-Si-F wood flour-based flame retardant was prepared according to the method described in the patent. First melt blending: PVC (45 parts), wood flour-based flame retardant (40 parts), zinc hydroxystannate (5 parts), stabilizer (5 parts), PE wax (0.3 parts), high-temperature internal lubricant (G60, 0.4 parts), and toughening agent (HL100, 4.5 parts) were thoroughly mixed in a high-speed mixer. The mixture was then fed into a twin-screw extruder for a first melt blend at 165 °C, and extruded to obtain a preliminary batch of composite material. Second melt blending: The preliminary batch of composite material was crushed and premixed with calcium powder (5 parts) in a high-speed mixer. This mixture was then fed into another twin-screw extruder for a second melt blend at 175 °C, and hot-pressed at 165 °C to obtain the final product.

[0042] The wood-plastic composite material prepared in this embodiment has a flexural strength of up to 60 MPa, a tensile strength of up to 65 MPa, a flame retardant performance of UL-94 V0 level, and a density of approximately 0.8 g / cm³.

[0043] Comparative Example 1:

[0044] In Specific Example 4, zinc hydroxystannate (5 parts) was replaced with zinc stearate (5 parts), while all other aspects remained unchanged.

[0045] The wood-plastic composite material in Comparative Example 1 has a flexural strength of 50 MPa, a tensile strength of 55 MPa, a flame retardant performance of UL-94 V0 level, and a density of approximately 0.8 g / cm³.

[0046] Comparative Example 2:

[0047] Replace the wood flour-based flame retardant (40 parts) in Specific Example 4 with unmodified wood flour (40 parts), while keeping everything else unchanged.

[0048] The wood-plastic composite material in Comparative Example 2 has a flexural strength of 40 MPa, a tensile strength of 45 MPa, no UL-94 flame retardancy rating, and a density of approximately 0.8 g / cm³.

[0049] Comparative Example 3:

[0050] The calcium powder (5 parts) in Specific Example 4 is not added, and everything else remains unchanged.

[0051] The wood-plastic composite material in Comparative Example 3 has a flexural strength of 63 MPa, a tensile strength of 67 MPa, a flame retardant performance of UL-94 V0 level, and a density of approximately 0.78 g / cm³.

[0052] Compared to Example 1 above, in Example 2, the amount of wood flour-based flame retardant was increased to 35 parts, and the content of zinc hydroxystannate was appropriately increased (4 parts), while the amount of calcium powder was slightly reduced (10 parts). The mechanical properties of the material were significantly improved, with a flexural strength of 50 MPa and a tensile strength of 55 MPa. This demonstrates the positive contribution of wood flour-based flame retardants to the mechanical strength of materials at high content, and may also be due to the reinforcing effect brought about by their modification. The synergistic effect of zinc hydroxystannate and wood flour-based flame retardant still ensures the UL-94 V-0 flame retardant rating. The reduction in density also shows the lightweight advantage brought about by increasing the proportion of wood flour.

[0053] In Case 3, the content of wood flour-based flame retardant was further increased to 40 parts, and zinc hydroxystannate also reached a relatively high value of 5 parts within the patent scope, while the amount of calcium powder was significantly reduced (5 parts). This formulation combination successfully improved the flexural strength and tensile strength to 60 and 70 MPa, respectively, while maintaining the UL-94 V-0 flame retardant rating. The significantly reduced density (0.8 g / cm³) further highlights the advantages of wood flour-based flame retardants in terms of lightweighting. This indicates that the high content of wood flour-based flame retardant and sufficient zinc hydroxystannate synergistically improve the mechanical strength of the material, and the material density decreases as the amount of wood flour-based flame retardant increases and the amount of calcium powder decreases.

[0054] Example 4 has a very similar formulation to Example 3, except for a relatively lower PVC content (45 parts). However, the overall performance is consistent, achieving flexural and tensile strengths of 60 and 65 MPa, respectively, and a low density of 0.8 g / cm³, while maintaining a stable UL-94V-0 flame retardant rating. This further confirms that within this formulation range, increasing the amount of wood flour-based flame retardant and decreasing the amount of calcium powder significantly enhances mechanical properties and lightweighting effects, and the synergistic flame retardant effect of zinc hydroxystannate and the multi-component wood flour-based flame retardant is evident. A moderate reduction in PVC content, without significantly affecting mechanical and flame retardant properties, helps to further reduce material density.

[0055] Furthermore, in Comparative Example 1, replacing zinc hydroxystannate with zinc stearate in Example 4 resulted in a decrease in both the flexural and tensile strengths of the wood-plastic composite material. This indicates that the presence of surface functional groups such as hydroxyl groups in zinc hydroxystannate increases interfacial compatibility and further enhances mechanical properties. In Comparative Example 2, using unmodified wood flour to replace the wood flour-based flame retardant significantly reduced mechanical properties, and the flame retardant performance failed to reach the UL-94 V0 rating. This demonstrates that the wood flour-based flame retardant of this invention is crucial for improving both flame retardant and mechanical properties. Comparative Example 3 shows that reducing or removing calcium powder has a positive impact on improving mechanical properties and weight reduction.

Claims

1. A high-strength, flame-retardant, lightweight wood-plastic composite material, characterized in that, It is composed of the following different components: PVC 40-70 parts Calcium powder 0-15 parts 20-55 parts of wood powder-based flame retardant 1-5 parts of zinc hydroxystannate stabilizer 3-10 parts PE wax 0.3-1 part High-temperature internal lubricant (G60) 0.3-1 part Toughening agent (HL100) 4.5-8.5 parts.

2. The high-strength, flame-retardant, lightweight wood-plastic composite material according to claim 1, characterized in that, It is composed of the following different components: 60 PVC 15 parts calcium powder 20 parts of wood powder-based flame retardant 3 parts zinc hydroxystannate stabilizer 4.8 parts 0.35 parts PE wax High-temperature internal lubricant (G60) 0.4 parts Toughening agent (HL100) 5.5 parts.

3. The high-strength, flame-retardant, lightweight wood-plastic composite material according to claim 1, characterized in that, The zinc hydroxystannate is a flame retardant and smoke suppressant for wood-plastic composite materials, the high-temperature internal lubricant is G60, and the toughening agent is HL100.

4. The high-strength, flame-retardant, lightweight wood-plastic composite material according to claim 1, characterized in that, The wood powder-based flame retardant is modified wood fiber, bamboo fiber, or rice husk powder.

5. A method for preparing a high-strength flame-retardant lightweight wood-plastic composite material according to claim 1, comprising PVC, wood powder-based flame retardant, zinc hydroxystannate, stabilizer, PE wax, high-temperature internal lubricant, and toughening agent in the stated component ratio, prepared by two melt blending processes, wherein the melt temperature is 165-175 ℃; characterized in that, The preparation process of the wood flour-based flame retardant is as follows: (1) To carry out the boronization reaction of wood flour, the wood flour is dispersed in an aqueous solution of sodium tetraborate decahydrate (Na2B4O7•10H2O), the pH is adjusted to 10, so that the boron element is modified and grafted onto the surface of the wood flour, and then dried. The boronized powder obtained is denoted as BF. (2) BF is placed in a certain chitosan solution. Through electrostatic action, chitosan is adsorbed onto the surface of BF and then dried. The resulting wood powder is called BNF. (3) BNF is placed in a certain phytic acid solution. Through electrostatic action, phytic acid is adsorbed onto the surface of BNF and then dried. The resulting wood powder is called BNPF. (4) In the same steps as above, Si elements are synergistically attached to the surface of wood flour BNPF through silane coupling agent to form wood flour BNP-Si-F modified with multiple flame retardant elements.

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