What are the process characteristics of plastic rod extrusion
What are the process characteristics of plastic rod extrusionWhen extruding plastic rods, in addition to reasonable control of the barrel temperature, the temperature and replenishment speed of the machine head and the hot and cold die parts should be properly controlled. This is the key to extruding high-quality rods.
(1) Amorphous plastic with high viscosity and poor fluidity. When extruding non-crystalline plastic rods such as polycarbonate, polysulfone, modified polyphenylene ether, etc., due to the poor fluidity of high viscosity plastics and the pressure of the plastic melt on the mold wall, the plastic shrinks in the mold , Generally increase the temperature of the barrel and the head temperature to increase fluidity. Such as polysulfone material temperature rise 20. C, its viscosity can be reduced by 1/2; the temperature of the cooling and setting die is 70 ～ 90 ℃, and the central melting process is short. At this time, the linear speed of the plastic rod extrusion should be low, so as to facilitate the rapid feeding, It can avoid the vacuum bubble in the center of the bar. At the same time, the clamping force of the damping machine is required to be smaller than that of the crystalline plastic rod.
(2) Crystalline plastic with low viscosity and good fluidity. Nylon bar is a typical plastic bar, so nylon plastic is used as an example. Due to the low viscosity and good fluidity of nylon, the linear velocity of the extruded rod is faster, and the center melt flow layer is longer than the cooling setting die. Nylon melt has a thin solidified layer on the inner surface of the mold, so defects such as non-round rods, perforation of the rod surface, flashing, and swelling often occur. Therefore, the temperature of the cooling and setting mold should be lower, preferably 40-60 ° C. In order to solve the problem of the center hole of the rod, it is necessary to replenish quickly. It is necessary to reduce the temperature of the homogenization section of the barrel, slow down the linear speed of the bar, and increase the temperature of the head to quickly replenish the material.
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