The molding methods of wood-plastic composite materials mainly include injection molding, extrusion molding, hot extrusion and cold pressing molding, and secondary processing such as thermoforming. The wood-biodegradable plastic composite system is a pseudoplastic fluid, and its viscosity is lower than the system filled with pure resin or other inorganic fillers. The low system viscosity is not conducive to the molding process, and the system viscosity is very sensitive to temperature. Increasing temperature can reduce the melt viscosity of the composite system, so strict attention should be paid to temperature control and adjustment during molding, especially extrusion molding. The preparation process of wood-biodegradable plastic composite material has a great influence on the performance of its products. The main difficulties of molding are as follows: poor dispersion and infiltration of wood fibers or excessive mixing which cause severe fiber damage; the degradation temperature and molding processing temperature of wood-plastic composite materials It is very close, and the temperature control must be very strict; the plant fiber will be partially or completely decomposed during the processing process to produce bubbles; the shearing force must be appropriate, and excessive shear or high temperature will cause discoloration and scorching. Therefore, wood-plastic processing equipment must have the following main technical characteristics: good dispersion and infiltration of wood fibers, resins, plasticizers, and other additives; good mixing and shearing functions, but shearing The force cannot be too high; there is a precise and sensitive temperature control system to achieve effective and stable control and adjustment of the entire heating and melting process; there is a good exhaust system, dehydration and volatilization, so that the product has no bubbles; there is a good cooling system , Especially for the production of thick wall products; the material of the plasticization system of the equipment should be heat treated well, so that the screw, barrel, etc. have sufficient wear resistance and service life. In addition, wood flour has poor heat resistance, easy to 'burn' above 180°C, discoloration in appearance, reduced bending performance and impact performance, high temperature, low system viscosity, insufficient extrusion pressure, difficult molding and processing, and unstable product quality. Under the same shear rate, the melt viscosity of the composite material at 160°C is an order of magnitude higher than the melt viscosity at 200°C. Therefore, the melt temperature of the system, especially the die temperature, should be as low as possible during the molding process. Regardless of the molding method, the processing temperature should be set correctly, and the adjustment should be paid attention to, and the shearing force should be reduced as much as possible. Therefore, the correct selection of molding processing equipment and molding process is an important aspect to ensure the quality of wood-plastic composite products. In addition, the wood powder used to make wood-plastic products must be dried to enable the molding process to proceed smoothly.
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