PP Polypropylene Chemical and physical properties PP is a semi-crystalline material. It is harder than PE and has a higher melting point. Since the homopolymer PP temperature is higher than 0 ° C is very brittle, so many commercial PP material is added 1 ~ 4% ethylene random copolymer or higher ratio of ethylene content of the claw-type copolymer. Copolymer PP material has a low thermal distortion temperature (100 ° C), low transparency, low gloss, low rigidity, but has a stronger impact strength. The strength of PP increases with increasing ethylene content. PP Vicat softening temperature of 150 ℃. Due to the high degree of crystallinity, the surface stiffness and scratch resistance of this material is very good.

PP does not exist environmental stress cracking problem. In general, PP is modified by the addition of glass fibers, metal additives or thermoplastic rubbers. PP flow rate MFR range of 1 to 40. Low MFR PP material has better impact resistance but lower ductility. For the same MFR material, the copolymer type has a higher strength than the homopolymer type. As a result of crystallization, PP shrinkage is quite high, generally 1.8 to 2.5%. And the direction of the uniformity of shrinkage than PE-HD and other materials much better. Adding 30% of the glass additive reduced the shrinkage to 0.7%. Both homopolymer and copolymer PP materials have excellent resistance to moisture absorption, acid and alkali corrosion resistance, anti-solubility. However, it has no resistance to aromatics (such as benzene) solvents, chlorinated hydrocarbons (carbon tetrachloride) solvents and the like.

Injection molding process conditions

Drying: Drying is not required if stored properly.

Melting temperature: 220 ~ 275 ℃, be careful not to exceed 275 ℃. Mold temperature: 40 ~ 80 ℃, it is recommended to use 50 ℃. The degree of crystallization is mainly determined by the mold temperature. Injection pressure: up to 1800 bar. Injection speed: Typically, the use of high-speed injection can reduce the internal pressure to a minimum. If there is a defect on the surface of the product, low-speed injection at higher temperatures should be used. Runners and gates: For cold runners, the typical flow path diameter range is 4 to 7 mm. It is recommended to use a circular inlet and a flow path. All types of gates can be used. Typical gate diameters range from 1 to 1.5 mm, but gate sizes as small as 0.7 mm can also be used. For edge gates, the minimum gate depth should be half the wall thickness; the minimum gate width should be at least twice the wall thickness. PP material can use hot runner system. 

Typical use

(The main use of metal additives containing PP: fender, ventilation ducts, fans, etc.), equipment (dishwasher door liner, dryer ventilation pipe, washing machine frame and cover, refrigerator door gasket, etc.), With consumer goods (lawn and gardening equipment such as lawn mowers and sprinklers).