Polycarbonate (PC) injection molding process

Date：2010/1/9 10:29:28

Polycarbonate (PC) injection molding process
 
    Non-crystalline polycarbonate plastic, odorless, tasteless, non-toxic, transparent amorphous plastic. Has excellent strength and toughness, high heat distortion temperature, excellent transparency features. As well as good dimensional stability and electrical performance.
Molding process:
① raw materials demanding custody, to prevent moisture, high temperature polycarbonate is very sensitive to the trace water, drying temperature is 110 ~ 120 ○ C for 24 hours continuously.
② no clear melting point of polycarbonate, injection molding temperature range from 240 ○ C ~ 310 ○ C are able to shape.超过 320 ○ C, has begun to decompose, forming, adjust the temperature of the pressure is more effective than regulation. General in order to let the plastic melt gradually, after the section of pipe in the feed / feed zone setting a lower temperature, feeding tube in front to set a higher temperature. However, if poorly designed screw, or L / D is too small, reverse-type set temperature is better.
③ mold temperature is too low, making prone to stress concentration, resulting in cracking, mold temperature requirements of 70 ○ C ~ 110 ○ C. High mold temperature can provide a better surface appearance, residual stress is also small and thin, or longer for moldings are easier to fill. However, low mold temperature is to shorten the molding cycle.
④ injection pressure: In order to quickly fill the mold cavity, injection pressure the bigger the better, generally about 850 ~ 1400kg/cm2, and up to 2400kg/cm2. The back pressure is the lower the better, but requires feed evenly, it is recommended to use a 3 ~ 14 kg/cm2.
⑤ injection speed and gate design has a lot, or the edge of the gate using the gate directly, in order to prevent Rihui phenomenon and the phenomenon of wave and current, then the application of a slow rate of fire, while the thickness of 5mm or more products; in order to avoid air bubbles and depression, slow rate of fire would be helpful, in general, the principle of a thin, quick rate of fire, thick are slow screw speed of 40 ~ 70RPM, but subject to machine design with screw adjustment.
⑥ barrel cleaning
In polycarbonate molding temperature, the addition of cleaning materials (general purpose polystyrene or through benzene) continuous injection, until the beginning Peng Zhang injection foaming cleaning material, and then re-set barrel temperature to 200 ~ 230 ○ C , continued air-launched following the cleaning materials, cleaning materials until the appearance looks very clean and transparent.
⑦ injection molding machine requirements:
  Clamping force: the projected area of ​​product per square centimeter by 0.47 ~ 0.78t (or per square when multiplied by 3 ~ 5t)
Injection volume: injection molding machine capacity is about 40% to 60% better.
Screw: length of at least 15 diameters long, the L/D20: 1 best compression ratio of 1.5:1 to 3.0:1 should

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