PBT and PET (polyester)

PBT + GF15

Good electrical and chemical properties and dimensional stability. PBT crystallizes quickly, PET more slowly (high mold temperature).

Processing temperatures

Melt (injection) temperature	265 °C
Mold surface temperature	75 °C
Ejection temperature	130 °C

Typical values. They vary (±) with grade and manufacturer; see the data sheet.

Physical properties (typical)

Density	1.42 g/cm³
Shrinkage (flow / cross)	0.5 / 1.3 %
Specific heat	1.15 kJ/kg·K
Thermal conductivity	0.23 W/m·K
Latent heat of crystallization (approx.)	42 kJ/kg

Drying

Drying is essential (PBT about 120 °C; PET about 150–160 °C).

For exact conditions see the material data sheet. Drying guide →

Points to watch

Moisture causes hydrolysis and lowers the strength considerably
Warpage in fiber-filled grades
High mold temperature for crystallization in PET

Typical use: Connectors, sensors, automotive electrics, covers and housings

Defects common with this material

Splay (silver streaks)

Fine silvery streaks on the part surface in the flow direction.

splay · silver streaks · moisture streaks

Brittleness / low impact strength

The part breaks more easily than expected; sometimes the surface looks fine.

brittleness · brittle part · cracking

Warpage

The part distorts or bends after it leaves the mold.

warpage · distortion · bowing

Sink mark

A dent on the surface opposite a thick section; the surface is drawn inwards.

sink mark · depression · sink

Dimensional variation and shrinkage differences

Part dimensions fall outside the tolerance or vary from cycle to cycle.

dimensional error · shrinkage · out of tolerance

Short shot (incomplete fill)

The cavity does not fill completely; the farthest or thinnest area of the part stays incomplete.

incomplete fill · underfill · non-fill

Other grades in the same family

Do the values for this material not match your grade? and we will correct them.