THE DEPENDENCE OF THE PATH DIFFERENCE ON ELASTIC AND HYPERELASTIC DEFORMATION FOR NETWORK POLYMERS

The dependence of optical path difference on elastic and hyperelastic deformation for network polymers was studied on the stages of loading- direct creep and unloading-reverse creep and also in the region of hyp erelasticity at cooling-down of a loaded sample. Birefringence is inde pendent of conditions of experiments and is a linear function of defor mation only. Because of linearity of path difference in deformations, one can consider physical properties as functions not of deformation b ut of path difference. The advantages this representation provides wer e illustrated on an example of determining intrinsic energy and entrop y per unit deformation in stressed polymers with varied network densit y.