plastic mould, injection mould

Polyethylene (PE) and injection molding process

PE for the crystalline material, moisture absorption is extremely small, not more than 0.01%, so no need to be dried before processing. PE molecules associated chain flexibility is good, key interactions among small, low melt viscosity, excellent mobility, so no high pressure molding can be a long process of forming a thin-walled products. PE shrinkage range, shrinkage of large, clear direction, LDPE shrink rate of about 1.22%, HDPE shrinkage rate of 1.5%. So easy deformation warpage, mold cooling conditions on the shrinkage rate greatly, it should be good control mold temperature, cooling to maintain uniform and stable. Crystallinity of PE high mold temperature on the plastic parts of the crystalline state has a greater impact. High mold temperature, melt cooled slowly, plastic parts with high crystallinity, high strength also. The melting point of PE is not high, but the specific heat capacity, so the plastics still need to consume more when the heat, and called plastination to have a larger heating power plant in order to improve production efficiency. 

PE softening temperature range is smaller, and melt easily oxidized, thus forming process in the melt should be avoided as much as possible into contact with oxygen in order to avoid lowering the quality of plastic moldsparts. PE workpiece soft texture, and easy mold release, so when the plastic parts with a light side of the groove can be powerful ejection. PE melt non-Newtonian behavior is not obvious, changes in shear rate has little effect on the viscosity, PE melt viscosity also less influenced by temperature. PE melt cooling rate slower, so must be fully cooled. Mold should have a better cooling system. If the PE melt in the injection molding by direct inlet feed, easy to increased stress and produce search uneven and significantly increased directional deformation, it should be noted that the feed port selected parameters. 
PE, wide molding temperature, the flow state, small fluctuations in temperature has no effect on the injection molding


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