Causes of opacity of polystyrene

Impurities such as inorganic fillers may exist in the screw, which leads to uneven crystallization after cooling and affects transparency. This is because polystyrene crystallizes after melt extrusion. When the grain size of crystal particles is larger than the wavelength of incident light, the material becomes opaque due to the refraction of incident light in the material.

Generally speaking, it can be summarized as follows:

1, impurities, screw self-cleaning ability is insufficient;

2, the temperature is not enough, or the temperature design is unreasonable.

Solution:

(1) Eliminate the interference of gas and other impurities, and fully dry the plastic.

(2) Reduce the material temperature, adjust the barrel temperature in stages, and appropriately increase the mold temperature.

(3) Increase the injection pressure and decrease the injection speed.

(4) Increase or decrease the back pressure of preform and reduce the screw speed.

(5) Improve the exhaust conditions of runner and cavity.

(6) Clean the nozzle, runner and gate to prevent blockage.

(7) Shorten the molding cycle, and remove the crazing by annealing after demoulding: for polystyrene, keep it at 78℃ for 65438 05 minutes, or at 50℃ for 65438 0 hours, and for polycarbonate, heat it to 65438 060℃ for several minutes.