Effect of pressure on thermal degradation of polyethylene

Abstract

A thermal degradation of polyethylene was carried out in a stirred tank reactor by continuous flow operation under elevated pressures ranging from 0.1 to 0.8 MPa, in order to investigate the effect of reaction pressure on thermal degradation behavior of polymers. Rate of volatilization, rate of double bond formation and the distribution of degradation products were studied at various temperatures and pressures under a steady state. It was found that the reaction pressure had a significant effect on both rates and the distribution of degradation products during thermal degradation of polyethylene. Since there exists a one to one correspondence between the double bond formation and the scission of CC links in polymers, it can be concluded that the reaction pressure takes part directly in the scission of CC links during thermal degradation of polymers. With the higher pressure, the carbon number distribution of gaseous and liquid products, and the molecular weight distribution of reactor contents shifted to the lower molecular weight side. Thermal degradation by continuous flow operation is a suitable technique for converting waste plastics into liquid hydrocarbons, which could be used as feedstock materials. The elevation of pressure during thermal degradation provides a potential alternative to control the distribution of products.