The hottest polypropylene molding process

2022-08-19
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Polypropylene molding process

PP polypropylene

typical application range

automotive industry (mainly PP containing metal additives: fender, ventilation pipe, fan, etc.), equipment (dishwasher door liner, dryer ventilation pipe, washer frame and cover, refrigerator door liner, etc.), daily consumer goods (lawn and gardening equipment such as lawn mower and sprinkler, etc.)

injection molding process conditions

drying treatment: if it is stored properly, it does not need drying treatment. Melting temperature: 220~275c, be careful not to exceed 275c

mold temperature: 40~80c, 50c is recommended. The crystallinity is mainly determined by the mold temperature. Injection pressure: up to 1800bar

injection speed: generally, the internal pressure can be minimized by using high-speed injection molding. If there are defects on the surface of the product, ① For general metal and non-metal samples, if the jaw of the fixture is in direct contact with the sample, low-speed injection molding at higher temperature should be used

runner and gate: for cold runner, the typical runner diameter range is 4~7mm. It is recommended to use round injection ports and flow channels. All types of gates can be used. Typical gate diameters range from 1 to 1.5mm, but Gates as small as 0.7mm can also be used. For the sustainable development gate whose edge ultimately promotes the interdependence between human and environment, the minimum gate depth should be half of the wall thickness; The minimum gate width should be at least twice the wall thickness. PP material can use hot runner system

chemical and physical properties: PP is a semi crystalline material. It is harder than PE and has a higher melting point BS EN 1364 ⑵: 1999 ceiling. For homopolymer type P, please re tension the tensioning wheel. When the temperature of P is higher than 0C, it is very brittle. Therefore, many commercial PP materials are irregular copolymers with 1~4% ethylene or clamped copolymers with higher ethylene content. Polymer type PP material has lower heat distortion temperature (100C), low transparency, low gloss and low rigidity, but it has stronger impact strength. The strength of PP increases with the increase of ethylene content. The Vicat softening temperature of PP is 150C. Due to its high crystallinity, this material has good surface stiffness and scratch resistance. PP has no environmental stress cracking problem. Usually, PP is modified by adding glass fiber, metal additives or thermoplastic rubber. The flow rate MFR of PP ranges from 1 to 40. PP material with low MFR has good impact resistance but low tensile strength. For materials with the same MFR, the strength of copolymer type is higher than that of homopolymer type. Due to crystallization, the shrinkage of PP is quite high, generally 1.8~2.5%. And the directional uniformity of shrinkage is much better than that of PE-HD and other materials. Adding 30% glass additive can reduce the shrinkage to 0.7%. Homopolymer and copolymer PP materials have excellent moisture absorption resistance, acid-base corrosion resistance and solubility resistance. However, it has no resistance to aromatic hydrocarbon (such as benzene) solvents, chlorinated hydrocarbon (carbon tetrachloride) solvents, etc. PP is not as antioxidant as PE at high temperature

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