Stress relaxation in molten polymers. II

摘要

AbstractA new analytical method is suggested for the evalution of the stress relaxation phenomena arising when a viscous flow of molten polymers is suddenly stopped. This method is based on the consideration of the relaxation isochronism and of other most typical features of the experimental stress–time relationships. Such features can be deduced by means of an analysis in elementary non‐Hookean bodies in series having a stress–time low of a particular analytical type. Such an analysis is applied to four samples of high and low pressure polyethylenes and natural rubber. The new parameters difined in this way are discussed in order to state some correlations with the structural features. Attention is drawn on the importance of an elasticity number defined as the ratio of the relaxation area to the corresponding Newtonian visc