Elastomers and special materials (TPU, TPE, EVA, CA)

TPU (Thermoplastic Polyurethane)

Flexible, soft-touch or special applications. Hardness (Shore) varies with the grade.

Processing temperatures

Melt (injection) temperature	210 °C
Mold surface temperature	40 °C
Ejection temperature	68 °C

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

Physical properties (typical)

Density	1.18 g/cm³
Shrinkage (flow / cross)	1.5 / 1.5 %
Specific heat	1.5 kJ/kg·K
Thermal conductivity	0.17 W/m·K
Latent heat of crystallization (approx.)	10 kJ/kg

Drying

Drying is essential for TPU; usually not required for TPE and EVA.

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

Points to watch

Low viscosity, risk of flash
Sticking in the mold and difficulty in ejection
Shrinkage differences and cooling can be long

Typical use: Seals, grips, coatings, shoe soles

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

Stress cracking

The part cracks during assembly, on contact with oil/solvent or over time; the crack usually starts at stressed areas.

stress crack · crack · environmental stress cracking

Weld line (knit line)

A line and a weak zone where two melt fronts meet.

weld line · knit line · joining line

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

Flash

Plastic escapes through the parting line or around the ejector pins.

flash · overflow · parting line flash

Other grades in the same family

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