U-PVC gelation level assessment, Part 1: Comparison of different techniques
Résumé
Several different gelation assessment methods such as differential scanning calorimetry, capillary rheometry, solvent absorption, wide angle x-ray scattering, transmission electron microscopy, and atomic force microscopy were applied to a typical PVC window profile formulation subjected to various thermomechanical histories. Shear applied during the process could be decomposed into two components: (i) a thermal component corresponding to the self-heating that was generated and (ii) a "mechanical" component associated with a "pure" shearing action deprived of any thermal aspect. Shear sensitivity of the above-mentioned gelation assessment techniques was evaluated by considering both aspects. Gelation levels established by differential scanning calorimetry and capillary rheometry were especially compared, thus allowing a comparison of the two physical aspects evidenced by each technique, i.e., crystallite melting and macromolecular network development. It appeared that as soon as the PVC particulate structure had been fragmented into micronic entities (primary particles) the gelation process was governed mainly by the thermal aspect, i.e., crystallite melting.