NEW METHOD FOR MEASURING THE NONELASTIC WORK-HARDENING RATE OF SOLID POLYMERS

Probing the non-elastic deformation of solid polymers in the pre-yield range has proved to be a very sensitive test of the structural response to plasticity nucleation. A work-hardening rate parameter, K, deduced from repeated stress relaxations was thus introduced to quantify this behaviour. It is shown that considerable improvement and more extensive information may be gained by measuring the work-hardening rate by the so-called direct method from a simple stress-non-elastic strain plot. A comparison is given of the two methods in the case of unsaturated polyester resins, together with a careful evaluation of potential sources of discrepancy.