PS material’s character and injection parameter
1. PS is an amorphous plastic with a wide melting temperature range and good thermal stability;
2. The heat distortion temperature is 70-100 ° C, the viscous flow temperature is 150-204 ° C, and decomposition occurs above 300 ° C;
3, PS melt viscosity sensitivity to temperature and sensitivity to shear rate are moderate, good fluidity, easy to form;
4. The water absorption of the PS resin is very low, generally 0.01 to 0.03%, and it may not be dried before molding. [If necessary, it may be dried in a circulating hot air of 70 to 80 ° C for 2 to 3 hours].
5. The temperature of the barrel during injection molding is controlled within the range of 180 to 215 °C, and the nozzle temperature is 10 to 20 ° C lower than the maximum temperature of the barrel.
6, the injection pressure is generally controlled at 60 ~ 150MPa. Large gates, simple shapes and thick-walled products, the injection pressure can be lower, about 60 ~ 80MPa.
7, easy to form internal stress and cause cracking, residual stress problems are more prominent. In order to reduce the internal stress, a higher material temperature and a mold temperature are often required for processing, so that the melt is slowly cooled, and the oriented molecules are relaxed. It is also possible to select a grade with high fluidity or to add a flow aid;
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