Physical interpretation of the rheological behaviour of amorphous polymers in the glass transition temperature range

Abstract

AbstractIn a previous work, we developed, from physical basis, a theory of the non‐elastic deformation of amorphous polymers which is observed through the glass transition temperature. In this model, it is assumed that density fluctuations (or defects) exist in thermal equilibrium (TTg) or are frozen in (T< Tg). The application of a stress results in the nucleation of shear ‐ microdomains (smd) near the defects (anelasticity). A subsequent Irreversible expansion of shear ‐ loops might occur thanks to monomer diffusion which is shown to be dependent on (I) the defect concentration Cd and (II) on hierarchical correlation effects. The dynamic modulus G' and G' (and tanφ) are calculated as a function of parameters which can be known from Independent experimental ways and all have a precise physical meaning. The most Important parameter is the mechanical relaxation time τm linked to Cd; thus, all changes in the microstructure (i. e. Cd) imply a variation of the dynamic modulus.The purpose of the present work is to make a comparison between the predictions of the model and experimental results obtained with polystyrene after different thermal histories.