Prediction of stress-relaxation and creep of linear aromatic polyesters related to poly(ethylene terephthalate) in the nonlinear range

A study of the nonlinear viscoelastic properties of polymers was made using the Halsey‐Eyring model with one‐ and three‐dimensional mathematical analyses. Various parameters to calculate stress–relaxation and creep could be calculated from a single stress–strain curve of the same polymer. The parameters so calculated reconstituted the stress‐strain curves, the one‐dimensional equations yielding the better fit. The same constants were applied to predict stress‐relaxation and creep. The fit using the three‐dimensional equations is much better for stress‐relaxation and creep than the one‐dimensional equations.