Thermo-oxidative degradation of polyolefines

Summary

Autooxidation of low density polyethylene has been studied in melt and in 1,2,4-trichlorobenzene solution. The kinetics of oxygen-absorption, concentrations of hydroperoxides, carboxyl, and other oxo groups and average number of scissions have been investigated. It has been found that the main features of the oxidative processes in solution and in melt do not differ significantly. However, the concentration of hydroperoxides as a function of conversion and the dependence of the maximum concentration of hydroperoxides on temperature make exception. There is a very good agreement between average number of chain scissions and carboxyl groups and this is independent of phase, concentration, temperature, and conversion. From one mole consumed oxygen approximately 0.6 ÷ 0.7 mole remains in the polymer backbone in the form of oxygen-containing functional groups. The ratio of average chain scissions to the formed carbonyl groups is 1∶5, i.e., functional groups form both at the chain ends, in consecutive reactions after the scission, and along the polymer chain.