PET Polyethylene terephthalate Typical applications: automotive industry, electrical components (motor housings, electrical couplings, relays, switches, microwave oven internal devices).
Injection Molding Process Conditions: Drying: Drying before processing is necessary because PET is more hygroscopic. It is recommended to dry at 120~165C for 4 hours. The required humidity should be less than 0.02%. Melting temperature: for unfilled type: 265~280C; for glass filling type: 275~290C. Mold temperature: 80~120C. Injection pressure: 300~1300bar. Injection speed: Higher injection speeds can be used without causing embrittlement. Runners and gates: All conventional types of gates can be used. The gate size should be 50~100% of the thickness of the plastic part.
Chemical and physical properties: The glass transition temperature of PET is around 165C, and the crystallization temperature range of the material is 120~220C. PET has a strong hygroscopicity at high temperatures. For glass fiber reinforced PET materials, bending deformation is also very likely to occur at high temperatures. The degree of crystallization of the material can be increased by adding a crystal strengthening agent. Transparent articles processed with PET have gloss and heat distortion temperatures. Special additives such as mica can be added to the PET to minimize bending deformation. If a lower mold temperature is used, a transparent article can also be obtained using a non-filled PET material.
PP polypropylene typical application range: automotive industry (mainly using PP with metal additives: fenders, ventilation pipes, fans, etc.), instruments (dishwasher door gasket, dryer ventilation pipe, washing machine frame and cover, refrigerator Door liners, etc.), consumer goods (turf and garden equipment such as lawn mowers and sprinklers, etc.).
Injection Molding Process Conditions: Drying: No drying is required if stored properly. Melting temperature: 220~275C, please be careful not to exceed 275C. Mold temperature: 40~80C, 50C is recommended. The degree of crystallization is mainly determined by the mold temperature. Injection pressure: up to 1800 bar. Injection speed: Generally, high-speed injection molding can be used to minimize internal pressure. If defects appear on the surface of the product, low speed injection at higher temperatures should be used.
Chemical and physical properties: PP is a semi-crystalline material. It is harder and has a higher melting point than PE. Since the PP temperature of the homopolymer type is very brittle when it is higher than 0 C, many commercial PP materials are random copolymers of 1 to 4% of ethylene or a clamp copolymer of a higher ratio of ethylene. The copolymer type PP material has a low heat distortion temperature (100C), low transparency, low gloss, low rigidity, but has stronger impact strength. The strength of PP increases as the ethylene content increases.
