The effect of thermal relaxations on the crack initiation resistance of rotomolded linear low density polyethylenes

The objective of this paper is to provide a better understanding of how test temperature and test frequency affect the crack initiation and propagation energies of rotomoulded materials. Trials were carried out on a range of rotomolded linear low density polyethylenes. Instrumented impact tests and dynamic mechanical thermal analysis (DMTA) were carried out on each material at a wide range of temperatures and frequencies. It was found that there is a linear relationship between the crack initiation energy of the samples and the tan δ values at all test conditions. By using this relationship it is possible to predict the crack initiation energy of a polymer part over a wide range of conditions by carrying out a small number of tests.