Tensile failure properties of some branched polyurethane elastomers

Abstract

Earlier papers have shown that the energy input to break obtained from tensile stress-strain curves for a crosslinked amorphous vulcanized rubber is exponentially related to the reciprocal of absolute temperature. These earlier investigations also showed that for both amorphous and crystalline rubbers the energy input to break over a range of temperature was related by a square law to the strain at break. This paper demonstrates that these relationships are obeyed by a series of branched polyurethane elastomers. By multiplying the strains at break on the energy input to break/strain at break graph by the parameter V e , the number of network chains per unit volume, the results for various degrees of branching are made coincident. When compared with earlier results from crosslinked rubber, it is found that a unique relationship involving only one numerical constant can be derived which is applicable to amorphous, crystalline and branched polymers at different degrees of crosslinking, whether filled or unfilled.