The processing method of the wood-plastic composite extrusion process is basically the same as the plastic processing method, and the main equipment seems to be roughly the same, but the difference is substantially different. The equipment currently available for extrusion of wood-plastic composites mainly includes twin-screw extruders and single-screw extruders. Single screw extruders typically accomplish the task of conveying and plasticizing materials. However, the traditional single-screw extruder is greatly restricted in the extrusion of wood-plastic composite materials, so the special design of the screw is required to make it have strong raw material conveying and mixing and plasticizing ability, so as to achieve the squeeze. The mixing and granulating process of the material is completed before exiting.
The twin-screw extruder feeds and processes the material by means of the positive displacement principle, which can be further divided into a parallel twin-screw extruder and a cone-type twin-screw extruder. The parallel twin-screw extruder can directly process wood flour or plant fibers, and the wood flour drying and molten resin processes can be carried out separately. Compared with the “mixing†type equipment, the tapered twin-screw extruder has a larger feeding section diameter, which can continuously compress the material, which can shorten the residence time of the material in the barrel, and the diameter of the metering section Small, the shear of the molten material is small, which is a big advantage for processing thermoplastic wood-plastic materials, so it is called "profile" type equipment with low speed and low energy consumption.
In addition, the extruder head and cooling sizing system are also important components related to the quality of the extruded product. Due to the particularity of wood-plastic composite materials and the high filling amount of wood powder, the extrusion material has poor fluidity and is not easy to cool. Conventional molds and sizing equipment can no longer meet the needs of the products, which makes the design of the machine head not only ensure the flow channel design. In addition to the smooth transition and reasonable flow distribution, it is also necessary to consider the pressure building capacity and temperature control accuracy of the machine head, and arrange the heating and cooling device of the machine head reasonably, so that the cooling speed is fast and the precision is high, so as to ensure the product quality. And the purpose of production.
Regardless of the type of processing, the mold is indispensable for the manufacture of wood-plastic products. Based on the thermal sensitivity of wood-plastic composites, wood-plastic molds generally use larger structural dimensions to increase heat capacity, which enhances the temperature stability of the entire head; while taking smaller values ​​along the extrusion direction to shorten material on-machine The length of stay in the head. In addition to the correct shape of the mold and the accuracy of the parameters, the surface treatment of the mold is also very important, especially in the extrusion processing.
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Label: Introduction of characteristics of wood plastic material production equipment
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