Relationship between temperature and chain transfer agent in the synthesis of low molecular weight poly(vinyl chloride) resin

Abstract

The synthesis of the molecular weight PVC resins is typically carried out at high temperature which results in high reaction pressure. Therefore, the safety must be carefully considered. Moreover, some properties of the produced PVC resin cannot be satisfactory achieved such as low porosity in which the amount of ungel PVC during processing will increase which results in the fish eyes on product surface. Another method for the synthesis of low molecular weight PVC is polymerization at lower temperature with the addition of chain transfer agent during the reaction. In this study, the low nolecular weight PVCs with K-value of 50 ± 1 was synthesized at 81℃ without addition of chain transfer agent. The polymerization temperature was then lowerd to 77, 73 and 69℃ along with the variations in the amount of chain transfer agent at each temperature to obtain the desired K-value. It was found the polymerization temperature decreased, more chain transfer agent was needed. At the polymerization temperature of 77, 73 and 69℃, the amount of chain transfer agent needed were 0.027, 0.047 and 0.080 phm, respectively. The PVC obtained from polymerization temperature of 69℃ showed the best physica properties, namely porosity , namely porosity, particle size and shape, size distribution coefficient, bulk density, fish eyes without influence to themal stability and mechanical properties.