**12.4 Stress relaxation**

Stress relaxation is a technique can be used as a physical method to determine the domain structure of the TPEs by studying the time-dependent deformation behaviour of the segmented block copolymer. There is no stress relaxation occurs in ideal elastomer.

## **12.5 Strain hardening**

At high strain, strain hardening takes place and converts TPE from elastic behaviour to leathery or stiffer characteristic so that elasticity is lost while tensile strength and modulus will be increased. In time, the recovery of the deformation occurs suggesting that the part where deformation occurs is viscoelastic.

### **12.6 Tear strength**

Tear strength which describes how well the elastomer resists tearing. TPE is stretched and the amount of force required is recorded. Peel strength is a measure of how well a TPE has bonded to a rigid substrate.
