The Studies of Rigid PVC Compounds: Morphology, Rheology, and Fusion Mechanism.

Morphological analyses of PVC, PVC/CPE, and PVC/CPE/OPE compounds were examined by scanning electron microscopy, transmission electron microscopy, and scanning-transmission electron microscopy. A correlation has also been established between the morphological analyses and the IZOD impact strength of PVC compounds. PVC compounds were prepared in a Haake Torque Rheometer using various blending conditions. The fusion level of processed compounds was evaluated by DSC thermal analysis and capillary rheological analysis, based on the heat of fusion and entrance pressure drop, respectively. S-shaped fusion curves were obtained. The effects of temperature, rotor speed, and totalized torque on the fusion level of PVC compounds were discussed. Also, the influence of temperature and rotor speed on the fusion time was studied. The morphological changes of the various fusion processes were characterized by SEM. The compounding energy was calculated by using an energy balance in an internal mixer (Pedersen, 1991). The compounding energy was then correlated with the fusion level, and the differences between experimental and theoretical results were compared and discussed. A 2$\sp3$ factorial experimental design was applied to study the main, two-factor interaction, and three-factor interaction effects of temperature, rotor speed, and totalized torque (TTQ) on the fusion of PVC compounds. The fusion characteristics of these PVC compounds (fusion time, fusion torque, and fusion temperature) were studied, and the surface morphological changes of these PVC compounds were also examined by SEM. The fusion mechanisms of these PVC compounds have also been postulated in this study