Properties and structures of films drawn from polyethylene single‐crystal mats

The properties and structures of polyethylene films drawn from mats of single crystals were investigated in comparison with films drawn from bulk polymer. The most important result obtained is that the structural reorganization stimulated by mechanical stress and annealing occurs with much greater difficulty in the mat‐drawn film. The chief mechanical characteristics of the film are a very low extensibility and a very high modulus. Structural characteristics, such as the double‐orientation of the crystalline region and the morphology of the crystals, do suffer no substantial changes during annealing at high temperatures. This stability of the structure can be related to the characteristic fine structure of the mat‐drawn film in which there are a much larger number of tie chains, connecting neighboring crystals, than in the bulk‐drawn specimen. Relaxation of the amorphous region and a notable increase in long spacing take place in the mat‐drawn sample as in ordinary bulk‐drawn samples. However, the morphological changes of the crystals accompanied by the folding back of chains seem to take place with great difficulty during annealing even in the vicinity of the melting point.