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Classification of wood plastic composite materials
According to the interface between wood and plastic, wood plastic composite materials can be divided into three types: plasticized composite with wood as the matrix, wood plastic fusion and wood plastic mixed composite.
The plasticized composite WPC with wood as the substrate is to inject plastic monomer or phenolic resin, urea resin, and polyester resin into solid wood. When plastic monomers are used as impregnants, because these monomers are generally non-polar compounds, they will not have a strong chemical reaction with the polar hydroxyl groups in the wood. They can only be used under the combined action of free radicals and heat sources. Plastic generates free radicals and polymerizes in wood, forming polymers that fill the cavities of fibers. The material composited by this method is also called plastic composite wood. Such a composite method can improve the dimensional stability, resistance to deformation, and corrosion resistance of the wood. Most of the monomers impregnated in the composite process use monomers such as styrene, vinyl chloride, acrylonitrile and methyl methacrylate.
Wood plastic melt is a new type of wood plasticization template technology, which uses wood flour or wood fiber and thermoplastic polymer materials to make composite materials. The manufacturing method of this composite material is to heat the wood flour and the polymer material together while fully mixing, inject into a mold or pave it into a board, and then make a finished product after hot pressing. The most researched now is to use polyethylene as the base material and wood flour or wood fiber as the filler to make composite materials. Because of the unique hydrophilic properties of wood during compounding, the water resistance is poor when the content of thermoplastic polymer is low.