Thermal Degradation of High Density Polyethylene

Abstract

Thermal degradation experimant of high density polyethyiene was carried out by using a continuous flow reactor in the temperature range of 4000 to 4450C under a. tmospher. jc pressure to investigate the rate of thermal degradation and properties of decomposition products at the steady state.The products of thermal degradation were separated into two parts, the one, vol, atile gaseous product at 25C and the other, less-volatile Qily product. The gaseoms product wasi. analyzed by gas chromatography and was found to be ceRsisted ef H2 and CitvC6 hydrocarbens, having the average molecular weight of 35 to 37. The composition of gaseotis products did not change appreeiably with the degradatien temperature. The oily product was found to be consisted of a wide spectrum of hydrocarbon fragment, saturated and unsatutated, varying in carbon numbers from 3 to 30 (see Fig.6, 7). The average molecular weight ef the oily product varied from 180 to 232 withx, degradatiop temperature (see Fig.9). Other physical properties of eily products are shown in Table 3.The average yield of product oil was 94.5% of the total products in the temperature range investigated. The reactor content was the degraded polymer and its molecular weight was decreased to about 1200. Some physical properties of the reactor contents are shown in Table 3. The correlation between the rate of decomposition of the polyethylene and the rate of formation of double bonds, was also investigated. Both rates are plotted in Fig, 4 as a function of the degradation temperature. Carbon-carbon double bonds were found in gaseous products, only product and reactor contents, but as shown in Fig.5, the increase in double bonds of the reactor content was negligible. The activation energies of thermal degradation of the polyethylene, calculated on the basis of the above two rates, were 47.5 kcal/mol and 49.4 kcal/mol, respectively.