Injection molding process of polypropylene PP

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Typical application range of polypropylene:
Automotive industry (mainly using PP with metal additives: fenders, ventilation pipes, fans, etc.), instruments (dishwasher door liners, dryer ventilation pipes, washing machine frames and covers, refrigerator door liners, etc.), day Use consumer goods (lawn and garden equipment such as lawn mowers and sprinklers, etc.).

Injection molding process conditions:

  1. The PP material will start to deteriorate from around 280 °C, so the heating temperature should be operated below 270 °C, and its molecular orientation is very strong. When molding at low temperature, it is easy to warp and twist due to molecular alignment.
  2. A high pressure molding machine must be used for high pressure forming.
  3. The retraction tilt may be magnified. The runners and gates must be designed for fluidity. Pay attention to controlling material temperature and modulus.
  4. The molding shrinkage rate is about 0.35%, the heating temperature is 180 to 300 ° C, the mold temperature is 20 to 80 ° C, the tube temperature is 220 to 270 ° C, the discharge temperature is 210 to 280 ° C, the injection pressure is 400 to 1000 kg / cm 2 , and the minimum operating temperature is 200 ° C.
  5. The gate design must pay attention to the adhesion of the molded product. The molded article must be designed to prevent dents and deformation. The forming shrinkage is about 0.8 to 1.5%.
  6. Use hot air drying and drying temperature is 60~90 °C, take 1 hour, the first section of tube temperature is 240~250 °C; the second section is 190~250 °C; the third section is 170~230 °C; the fourth paragraph is 150~210 °C; mold surface temperature 20~60 °C.
  7. Temperature setting: nozzle 200~220°C, front section 190~215°C, middle section 190~210°C, rear section 185~200°C; screw speed 120~max rpm, mold temperature 20~70°C, injection pressure 700~1800°C The pressure is extremely long 30~70%, and the back pressure is 120~200kg/cm2.
  8. The density is 0.90~0.91g/cc, the specific gravity is 0.9~0.92, the linear expansion coefficient is 0.000058~0.0001/°C, the molding shrinkage is 1.0~2.5%, and the heat distortion temperature is 57~63°C (96~110°C).

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