PET processing conditions

PET processing conditions

Generic Class

PET (Polyethylene terephthalate)

Typical Applications

Automotive (structural components such as mirror backs, and grille supports, electrical parts such as head lamp reflectors and alternator housings), electrical applications (motor housings, electrical connectors, relays, and switches, microwave oven interiors, etc.), industrial applications (furniture chair arms, pump housings, hand tools, etc.).

Injection molding processing conditions

Drying

Drying is essential prior to molding. PETs are very sensitive to hydrolysis. Recommended drying conditions are 120 - 165 C (248 - 329 F) for 4 hours. The moisture content should be less than 0.02%.  

Melt Temperature 

265 - 280 C (509 - 536 F) for unfilled grades
275 - 290 C (527 - 554 F) for glass reinforced grades

Mold Temperature

80 - 120 C (176 - 248 F); preferred range: 100 - 110 C (212 - 230 F)

Material Injection Pressure

30 -130 MPa

Injection Speed

High speeds without causing embrittlement 

Runners and Gates

All conventional types of gates may be used; gates should be 50 - 100% of the part thickness.

Chemical and Physical Properties

PET is an aromatic polyester produced from polymerization of either terephthalic acid (TPA) or dimethyl ester terephthalic acid (DMT) and ethylene glycol (EG). The glass transition is approximately 165 C (330 F) and the material crystallizes over a temperature range from 120 - 220 C (248 -428 F).

PET is highly sensitive to moisture at high temperatures and exhibits excessive warpage when reinforced with glass fibers. Promotion of crystallinity is achieved through adding nucleating agents and crystal growth accelerators. Crystalline moldings exhibit high modulus, gloss, and heat distortion temperatures. Warpage is minimized by addition of particulate fillers such as mica. When low mold temperatures are used, transparent moldings


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