Appropriate additives are needed to modify the surface of polymer and wood flour to improve the interface affinity between wood flour and resin.
The dispersion effect of wood flour with high filling amount in the molten thermoplastic is poor, which makes the melt fluidity poor and the extrusion process difficult. Surface treatment agent can be added to improve the fluidity to facilitate the extrusion process.
The plastic matrix also needs to add various additives to improve its processability and the use performance of its products.
The wood flour structure is loose, and it is not easy to feed the extruder screw. Especially, the phenomenon of "bridging" and "holding pole" often occurs when the wood flour contains more water.
The instability of feeding will lead to extrusion fluctuation, resulting in the reduction of extrusion quality and output. The interruption of feeding will prolong the residence time of the material in the barrel, which will lead to the burning and discoloration of the material and affect the internal quality and appearance of the products.
The forced feeding device and reasonable conveying mode are adopted to ensure the stability of extrusion.
Exhaust during processing
The small molecule volatile matter and water contained in wood flour are very easy to bring defects to products, and the pretreatment cannot completely remove them. Therefore, more attention should be paid to the design of exhaust system of wood plastic composite extruder than that of ordinary plastic extruder. If necessary, multi-stage exhaust can be carried out.
To a large extent, the better the exhaust effect, the better the quality of extruded products.