APPLICATION OF MECHANICAL AND DIELECTRIC SPECTROMETRY FOR THE BEHAVIOR OF POLY(ETHYLENE-TEREPHTHALATE) - INFLUENCE OF CRYSTALLINITY

In order to correlate crystallinity and dynamic mechanical properties, poly(ethylene terephthalate) (PETP) samples were prepared and subject ed to viscoelastic measurements. The evolution of the glass-rubber tra nsition is analyzed for samples annealed at different temperatures. Mu ltiplexing analysis allows to draw the Cole-Cole plot and to develop a rheological model for the polymer behaviour. In the case of the amorp hous PETP, the asymmetric Cole-Cole plot may be represented by a ''bip arabolic'' rheological model. On the other hand, for the semi-crystall ine polymer, the Cole-Cole plot is symmetrical and the corresponding r heological model is the ''liquid Cole'' one. Dielectric spectroscopy e xperiments are in good agreement with the previous method. Particularl y, the Cole-Cole plot for semi-crystalline samples is perfectly symmet ric. The previous rheological models with, in addition, a static modul us are applicable to glass-fibre reinforced PETP. These new models are called ''limited biparabolic'' and ''Zener parabolic'' model, respect ively.