What technical issue of WPC machinery and WPC raw material
Technical issue of WPC raw material
Plastic raw material
Because 200 ° C is the upper limit of the processing temperature of wood-plastic composite materials, some resins with melting points exceeding 200C, such as PET, cannot be used in wood-plastic composite materials.
Moisture of material
Water vapor can degrade the properties of the composite and also help to breed microorganisms, so it must be removed before using wood fillers. The wood filler is dried before processing. Generally, the moisture content after the treatment is less than 1 ~ 2%.
Chemical additives
Appropriate additives are needed to modify the surface of the polymer and wood flour to increase the interfacial affinity between wood flour and resin.
Percentage of wood powder
High-filled wood flour has poor dispersion effect in molten thermoplastics, making the melt fluid poor, and extrusion molding processing difficult. Surface treatment agents can be added to improve fluidity to facilitate extrusion molding.
Plastic substrates also need to add various additives to improve its processing properties and the use of its products.
Technical issue of WPC machinery
Main machinery needs
Wood-plastic composite material processing machinery requires feeding equipment, drying equipment, extrusion equipment and molding equipment, as well as some necessary downstream equipment such as cooling water tanks, traction equipment and cutting equipment.
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Forced Feeding device
The structure of the wood flour is fluffy, and it is not easy to feed the extruder screw. In particular, the phenomenon of "bridge" and "holding pole" often occurs when the wood flour contains more water.
Feeding instability can cause extrusion fluctuations, resulting in reduced extrusion quality and yield. Feeding is interrupted, and the residence time of the material in the barrel is prolonged, which causes the material to burn and discolor, which affects the inherent quality and appearance of the product.
Forced feeding device and reasonable conveying method are adopted to ensure the stability of extrusion.
Moisture exhausting system for extruder
The small-molecular volatile substances and moisture contained in wood flour can easily cause defects in the product, and the pre-treatment cannot completely remove them. Therefore, the design of the exhaust system of the wood-plastic composite extruder should be given more attention than the ordinary plastic extruder, and multi-stage exhaust can be performed if necessary.
To a large extent, the better the exhaust effect, the better the quality of the extruded product.
Reasonable screw design
During the extrusion of wood-plastic composite materials, the configuration of the screw plays a very important role. The reasonable screw structure can reduce the friction between the screw and the wood fiber, and produce appropriate shear and dispersion mixing, so that the material system containing a large amount of wood flour can be well plasticized uniformly.
sufficient pressure die head and good calibration
In addition to ensuring a smooth transition and reasonable flow distribution in the flow channel design, the wood-plastic composite material has higher requirements for the pressure build-up capability and temperature control accuracy.
In order to obtain good fiber orientation and product quality, it is necessary to ensure that the machine head has sufficient pressure build-up capacity and long shaping section, and even adopts a double taper structure in the compression section and the shaping section.
Wood-plastic composites have poor thermal conductivity, and their products are mostly shaped materials, which are difficult to cool and shape, and water-cooled shapes are mostly used. The reasonable design of the cooling channel ensures efficient cooling.
