Thermal and mechanical properties of oriented polyethylene treated with nitric acid

Abstract

Filaments of linear polyethylene stretched at different draw ratio were immersed in fuming nitric acid for periods of time ranging from 0 to 7 h. Analysis of the groups formed was carried out by IR spectroscopy. The presence of nitrite groups at the early stages of nitration was found for the first time. However the samples did not show any weight loss, but a limited change in molecular weight. Changes in thermal properties and dynamic mechanical relaxation were also studied. Moreover, shrinkage stress which developed when the filaments were heated under fixed ends showed a steady decrease with etching time. At 7 h, the shrinkage stress decreased to a value similar to that produced by annealing for one hour. © 1983 The Society of Polymer Science, Japan.