Thermal Stability of Hydrocarbon Networks by Chemical Stress Relaxation

The thermal stability of hydrocarbon networks by chemical stress relaxation was investigated in vacuum and in the temperature ragne 300C - 350C. The polymers studied were low density polyethylene, high density polyethylene and ethylene-propylene terpolymer. Carbon-carbon crosslinked networks were produced either by dicumyl peroxide or by radiation. The results show that the overall thermal stability is in the order: peroxide cured EPT > peroxide cured LDPE > peroxide cured HDPE > radiation cured HDPE. The results are in apparent contradiction to the belief that linear structures are more stable than branched structures. We believe that this can be explained in terms of weak linkages introduced during curing. Scission probably occurs at weak linkages, at crosslinkages, and along the main chain. (Author)