MISCIBLE BLENDS FROM RIGID POLYVINYL-CHLORIDE) AND EPOXIDIZED NATURAL-RUBBER .1. PHASE MORPHOLOGY

Miscible blends of rigid poly(vinyl cloride), PVC, and epoxidized natural rubber (ENR) having 50 mol% epoxidation level, are prepared in a Brabender Plasticorder by the melt-mixing technique. Changes in Brabender torque and temperature, density, dynamic mechanical properties and DSC thermograms of the samples are studied as a function of blend composition. The PVC-ENR blends behave as a compatible system as is evident from the single Tg observed both in dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The moderate level broadening of the Tg zone in blends is due to microinhomogeneity, which may arise from the particle structures of PVC perturbing the molecular level mixing of PVC and ENR. Scanning electron microscopic studies were conducted on nitric acid-etched samples and the results showed continuous structures of blend components as well as the occurrence of solvent-induced cracks in high PVC blends.