Application de la spectrométrie mécanique et diélectrique à i'analyse du comportement du poly(téréphtalate d'éthylène). Influence de la cristallinité

In order to correlate crystallinity and dynamic mechanical properties, poly(ethylene terephthalate) (PETP) samples were prepared and subjected to viscoelastic measurements. The evolution of the glass-rubber transition is analyzed for samples annealed at different temperatures. Multiplexing analysis allows to draw the Cole-Cole plot and to develop a rheological model for the polymer behaviour. In the case of the amorphous PETP, the asymmetric Cole-Cole plot may be represented by a “biparabolic” rheological model. On the other hand, for the semi-crystalline polymer, the Cole-Cole plot is symmetrical and the corresponding rheological model is the “liquid Cole” one. Dielectric spectroscopy experiments are in good agreement with the previous method. Particularly, the Cole-Cole plot for semi-crystalline samples is perfectly symmetric. The previous rheological models with, in addition, a static modulus are applicable to glass-fibre reinforced PETP. These new models are called “limited biparabolic” and “Zener parabolic” model, respectively.