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.