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Analysis of the causes of transparent defects in injection moulded products

Update:19 Oct 2018
Summary:

Melting, silver, cracked polystyrene, transparent parts […]

Melting, silver, cracked polystyrene, transparent parts of plexiglass, sometimes through the light can see some sparkling filament-like silver. These silver streaks are also known as spots or cracks. This is because the stress in the vertical direction of the tensile stress is generated, and the weight of the polymer molecule is expressed by the heavy flow orientation and the difference in the folding rate of the unoriented portion.

Solution:

(1) Eliminate interference from gases and other impurities, and dry the plastic sufficiently.

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

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

(4) Increase or decrease the pre-plastic back pressure and reduce the screw speed.

(5) Improve the flow path and cavity exhaust conditions.

(6) Clean up possible blockages in the nozzles, runners, and gates.

(7) Shorten the moulding cycle, and eliminate the silver streaks by annealing after demoulding: keep the polystyrene at 78 ° C for 15 minutes, or 50 ° C for 1 hour, and heat the polycarbonate to 160 ° C for more than a few minutes. .

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