Composite materials are materials with new properties composed of two or more materials with different properties through physical or chemical methods. Various materials learn from each other in performance and produce synergistic effect, so that the comprehensive performance of the composite is better than that of the raw materials to meet various requirements. The matrix materials of composites are divided into metal and non-metal.

The molding methods of composites are different according to the matrix materials. There are many molding methods of resin matrix composites, including hand paste molding, spray molding, filament winding molding, molding, pultrusion molding, RTM molding, hot pressing tank molding, diaphragm molding, migration molding, reaction injection molding, soft film expansion molding, stamping molding, etc. The forming methods of metal matrix composites are divided into solid-phase forming method and liquid-phase forming method. The former is formed by applying pressure at a temperature lower than the melting point of the matrix, including diffusion welding, powder metallurgy, hot rolling, hot drawing, hot isostatic pressing and explosive welding. The latter is to melt the matrix and fill it into the reinforcement materials, including traditional casting, vacuum suction casting, vacuum back pressure casting, squeeze casting and spray casting. The molding methods of ceramic matrix composites mainly include solid-phase sintering, chemical vapor infiltration molding, chemical vapor deposition molding and so on.

Wood plastic composites (WPC) is a new type of composite materials booming at home and abroad in recent years. It refers to the use of polyethylene, polypropylene and polyvinyl chloride to replace the usual resin adhesive, and mix with more than 50% of waste plant fibers such as wood powder, rice husk and straw to form new wood materials, which are then processed by plastic processing processes such as extrusion, molding and injection molding, Produced plate or profile. It is mainly used in building materials, furniture, logistics and packaging industries. The extruded wood plastic composite plate is the plate formed by hot extrusion after mixing plastic and wood powder in a certain proportion.

According to the 2017-2022 Research Report on China's wood plastic composite market supply and demand investigation and analysis and investment planning recommendations released by Bosi data, in terms of industrial structure, there are about 3000-4000 enterprises in the composite industry, but only more than 180 enterprises above Designated Size, and only a few large enterprise groups with annual sales of more than 2 billion, such as Zhongfu group and Sinoma technology. The degree of industrial integration is not high, the proportion of small enterprises is too large, and the quality and technical level of employees are uneven. Industry oriented integrated technology innovation is weak, product research and development is not enough, and most of the medium and low-grade products.

In terms of market structure, large-scale application markets with an output value of more than billions mainly include wind power, chemical storage tanks, water pipelines, electrical insulation, boats, cooling towers, sanitary ware and other fields. More application markets such as automobile, light housing, urban infrastructure, animal husbandry, environmental protection, sports and leisure need to be further developed.

With the rapid development of economy, plastic products are more and more widely used in life, and the subsequent problem of "white pollution" has become a difficult problem in the cause of environmental protection. In recent years, plastic recycling has become the key development direction of plastic industry technology. In this case, wood plastic composites made of waste wood chips and waste plastics came into being. This new composite material is made of plastic raw materials such as polyethylene, polypropylene and polyvinyl chloride instead of the usual resin adhesive, and then mixed with waste plant fibers. It has irreplaceable advantages of ordinary plastic profiles, such as color, texture, light weight, nailing, sawing, drilling, planing, painting and other processing properties. At the same time, it also has the corrosion resistance that ordinary wood does not have Not resistant to acid and alkali, flame retardant and other advantages.

Wood plastic composites are widely used not only because it overcomes the limitations of low strength, large variability of traditional wood and low elastic modulus of organic materials, but also because it has made a certain contribution to reducing environmental pollution, reducing the amount of raw wood and protecting forests as a new green and environmentally friendly wood. Because wood plastic composite materials are processed from various waste plastics and waste wood, and the materials themselves can also be recycled, it greatly slows down the environmental pollution caused by the incineration of plastic waste and agricultural waste. It is a new green environmental protection product.