PBT and PET (polyester)

PBT + GF20

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

These values are for plastic injection molding (not valid for extrusion, blow molding, etc.) and are typical for a general grade; for a specific brand/grade see the supplier data sheet.

Processing temperatures

Melt (injection) temperature	267 °C
Mold surface temperature	77 °C
Ejection temperature	133 °C

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

Physical properties (typical)

Density	1.46 g/cm³
Shrinkage (flow / cross)	0.43 / 1.23 %
Specific heat	1.12 kJ/kg·K
Thermal conductivity	0.24 W/m·K
Latent heat of crystallization (approx.)	39 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.

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