Runaway phenomena in the ethylene/vinylacetate copolymerization under high pressure

Abstract

Ethylene is an `endothermic' compound. Above certain pressure and temperature it can decompose explosively into carbon, hydrogen and methane. The high pressure polymerization and copolymerization of ethylene can lead to thermal runaways, ethylene decomposes during polymerization. The influence of vinylacetate on the thermal runaway of ethylene during the copolymerization was investigated in the pressure range of 25–125 MPa and temperatures of 250–375°C. Decomposition boundaries above which ethylene violently decomposes have been established for the mixture of 10 and 30 wt.% vinylacetate. As well as the decomposition limit, maximum explosion pressure, maximum rate of pressure increase, maximum explosion temperature and composition of the produced gases are reported. The results show that the addition of vinylacetate lowers the decomposition boundary of ethylene. The lowering of the limit depends on initial pressure and composition of the mixture. The maximum rate of pressure increase and maximum explosion temperature are not influenced by vinylacetate. However, the maximum explosion pressure is about 20 MPa higher than for pure ethylene. Carbon monoxide, carbon dioxide and water are additionally produced when vinylacetate is present. The composition of the decomposition products depend on the initial pressure, wall temperature and concentration of vinylacetate.