Annealing of polyethylene single crystals

Abstract

Annealing of polyethylene single crystals in a temperature range of between 90° and 110°C has been studied by electron microscopy. Under the conditions employed, single crystals exhibited various aspects of transformed morphology without appreciable changes in their long periods. Morphological transformation is described in terms of ‘stage’, which is tentatively defined as the extent of annealing by the characteristics developed in morphology. Selective transformation was observed in the 100 sectors of specimens crystallized in different ways. It was found that each sector begins its transformation at a temperature characteristic for that sector. Molecular tilt around the b-axis was observed below 110°C. Lamellar thickening was found at temperatures higher than 110°C, while the orientation of crystallographic axes became random in the temperature range of interest. On the other hand, morphological change took place at all temperatures depending on the annealing temperature and time.