Research on extrusion process and performance of wood-plastic composite equipment

Source：ZHANGJIAGANG CITY FARCREATIVE PLASTIC MACHINERY CO LTD　Release time：2022-05-24 16:47:43　Author：1117

Wood plastic, that is, wood plastic composites (WPC), mainly uses waste plastics instead of commonly used resin adhesives, and wood flour, rice husks, agricultural straws and other plant fibers as raw materials. A new type of modified environmental protection Materials, widely used in construction, furniture, packaging, gardening, transportation and other industries.

As an important branch in the field of composite materials, the related research of WPC has been highly valued, mainly including several aspects, such as: the physical and mechanical properties of WPC, the interfacial compatibility between wood and plastic, and the control of the preparation process.

At present, the main molding methods used in its industrial production are extrusion molding, injection molding and hot pressing. Compared with other processing methods, extrusion molding has a wider application in industrial production due to its short processing cycle, high efficiency and simple molding process.

Far Creative WPC extrusion molding technology

Extrusion molding, also known as extrusion molding or extrusion molding, is a molding process in which the heated and melted plastic is forced to pass through the die under the pressure of the extrusion action of the screw to become a continuous profile with a constant cross-section. method.

Almost all thermoplastics can be formed by extrusion. The products produced include pipes, plates, cable coverings and composite materials of plastics and other materials. It is a molding method with high production efficiency, wide application and strong adaptability. When used in the production of wood-plastic composite materials, the extrusion process has the advantages of stable product quality, low cost, and relatively low investment, so it develops rapidly.

The main equipment for producing wood-plastic composites by extrusion method is screw extruder, including single-screw extruder, parallel twin-screw extruder and conical twin-screw extruder.

The single-screw extruder is characterized by high and stable pressure of the molten material at the head, but low mixing efficiency, so it is generally used for extrusion and granulation of profiles that do not require high mixing efficiency. The structure of the single screw extruder is relatively simple and the price is not high.

The twin-screw extruder, especially the meshing co-rotating twin-screw extruder, is characterized by large shear force and high mixing efficiency, but the melt pressure control is not as stable as that of the single-screw extruder, so the twin-screw extruder is mainly used for mixing. Occasions where high efficiency is required, such as fusion of fibers and plastics. The twin-screw extruder has a complex structure, and the price is generally several times that of the single-screw extruder with the same screw diameter.

Of course, if the twin-screw extruder and the single-screw extruder are combined in series, and combined with the profile auxiliary unit to form a profile extrusion production line, they can give full play to their respective advantages. It not only reduces energy consumption, but also helps to reduce thermal degradation of materials.

The conical twin-screw extruder has attracted much attention in recent years. Its mixing ability of materials is stronger than that of single-screw extruder, and the extrusion pressure is larger than that of twin-screw extruder, which can be used to directly extrude profiles. Not only that, but also has the characteristics of large material compression ratio, which is an outstanding advantage of the machine for extrusion processing of wood-plastic composite materials with low bulk density of raw materials. However, there are advantages and disadvantages. In terms of mixing efficiency, the conical twin-screw extruder is far less than the parallel twin-screw extruder.

Performance comparison of different resin-based wood-plastic composites

Since the wood fiber fillers used in wood-plastic composite materials can generally withstand a maximum processing temperature of 200 °C, wood-plastic composite materials usually use thermoplastic resins with relatively low processing temperatures such as PE, PP, and PVC. There is a big difference in performance.

The rigidity and tensile strength of PE are small. Compared with other polymers, PE has excellent properties of flexural resistance, water resistance, chemical resistance and low temperature flexibility, good processing performance and low price. Among them, HDPE has higher tensile strength, surface hardness and stiffness than LDPE. With the continuous improvement of people's living standards, people's requirements for the performance and texture of wood-plastic composite materials are also increasing. Therefore, at present, HDPE resin is used as the matrix. Wood-plastic composite materials account for the majority and are generally used for outdoor components.

The viscosity of PP melt is small, the temperature sensitivity is not large, and the processing performance is good. Compared with HDPE, it has higher tensile strength, surface hardness, tensile yield strength and stiffness, but is brittle at low temperature. The weather resistance of PP-based wood-plastic composite materials is not as good as that of PE-based wood-plastic products, which limits its application range to a certain extent.

PVC has the advantages of high rigidity, high strength and low price, and has good adhesion and coloring properties, but its cold resistance, aging resistance and thermal stability are poor, and its processing performance is poor. These shortcomings can be improved by adding additives. , such as plasticizers, stabilizers, lubricants, ACR impact additives. PVC has high melt strength and can be used to prepare wood-plastic foamed composite materials. PVC-based wood-plastic composite materials are mainly used in interior decoration materials.

At present, people are paying more and more attention to ecological problems and resource crisis. Therefore, people have also set off a new upsurge in the research of wood-plastic composite materials. After the emergence of wood-plastic composite materials, natural resources have been fully utilized, reducing environmental pollution problems caused by waste plastics, waste furniture and waste wood products. Although our country started relatively late in this regard, the development speed is very fast, and the industrialized production and processing technology is gradually becoming mature.

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