Impact strength

Impact strength

The Charpy impact bending test is a simple and rapid test that can be used to conduct a comparative assessment of different materials. It is employed, among other things, to study the effect of changed formulation conditions, compounding conditions and injection molding conditions on test specimens. In the Charpy test, specimens are subject to a loading configuration similar to that in the three-point bending test and, if they are sufficiently brittle, they will fracture. Notched specimens must be used to achieve fracture in ductile materials. The test can be carried out within a temperature range of –40 °C to +23 °C.

Compared with other materials, Desmopan® attains very high impact strength and notched impact strength values. On account of the elastic properties of TPU, there is no breakage above the glass transition temperature (Tg). The following table shows a number of characteristic values for reinforced Desmopan grades:

Desmopan® grade Impact strength Notched impact strength
385 23 °C: no fracture Fracture as of – 50 °C
DP.9662DU 23 °C: no fracture Fracture as of – 30 °C
KA8377 23 °C: no fracture Fracture as of – 30 °C
DP.3970D 23 °C: no fracture 23 °C: 60 kJ/m²
DP.3970D -30°C: 80 kJ/m² -30 °C: 14 kJ/m²

Results of the test method:

  • impact strength aiU [KJ/m2]
  • notched impact strength aiN [KJ/m2]
  • plus an assessment of specimen fracture at the corresponding temperature and, where appropriate, a tough/brittle transition

Standards: DIN EN ISO 179

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