Effect of Aging on Film Properties of Ethylene-Alpha-Olefin Copolymers

Film toughness measurements of certain ethylene-alpha-olefin copolymers of high impact strength, show significant aging effects, decreasing with time. In this work we studied the time and temperature dependence of film aging of several copolymers of varying molecular structure. Film aging appears to be associated with the presence of highly branched polymer chains (>30 branches per 1000 carbon atoms). It is speculated that the thermally activated rearrangement of such branched species, over time and under film storage conditions, leads to film aging. Higher film storage temperatures lead to faster aging. It is possible to employ an “accelerated aging” testing protocol to predict longer-term aged data from a short-term test, which would be useful in an industrial production setting.