PET materials

Polyethylene terephthalate (PET) has excellent chemical resistance and barrier properties, good strength, rigidity, fatigue endurance, and abrasion resistance.

Typical Applications

• automotive

  • mirror backs
  • grille supports
  • head lamp reflectors
  • alternator housings

• electrical applications

  • motor housings
  • electrical connectors
  • relays
  • switches
  • microwave oven interiors

• industrial applications

  • furniture chair arms
  • pump housings
  • hand tools

Injection molding processing conditions

Drying

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

Melt Temperature

• 265°C–280°C [509°F–536°F] for unfilled grades,
• 275°C–290°C [527°F–554°F] for glass reinforced grades

Mold Temperature

• 80°C–120°C [176°F–248°F]
• Preferred range: 100°C–110°C [212°F–230°F]

Material Injection Pressure

30 MPa-130 MPa

Injection Speed

High speeds without causing embrittlement

Runners and Gates

All conventional types of gates can 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°C–220°C [248°F–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 the addition of particulate fillers such as mica. When low mold temperatures are used, transparent moldings can be obtained with unfilled PETs.