Dynamic mechanical spectra and limit of linear viscoelasticity of high polmers

The dynamic mechanical properties of a typical polycrystalline polymer (polyethylene) and a typical glassy state amorphous polymer (polystyrene) have been studied as a function of both frequency and temperature. The response of these materials to mechanical loading was found to be dependent upon the magnitude of strain resulting from the mechanical load above the limit of linear viscoelastic response. Therefore, the limit of linear viscoelastic response must be considered as an important material characteristic in design application of high polymers. This limit has been studied as a function of time scale of loading and polymer structure for a series of materials. A general trend of increased strain limit of linear viscoelastic response with increased heterogeneity of internal structure has been found.