Tensile drawing behaviour of a linear low-density polyethylene: Changes in physical and mechanical properties

Abstract

The tensile drawing behaviour at 80°C of a linear low-density polyethylene has been investigated with particular attention to the changes in crystallinity, molecular orientation and mechanical properties. It was found that the more defective crystals were destroyed during drawing and rebuilt into more perfect crystals. Moreover, the crystallinity was improved by the strain-induced crystallization of initially amorphous chains. The crystalline chains quickly reached a nearly perfect orientation upon drawing, while the amorphous chains exhibited a slow and poor orientation. This contrasted with the spectacular increase in the tensile modulus of the fibres. It was suggested that the fibre stiffness is more sensitive to the number of intercrystalline tie molecules than to the chain tautness. On the other hand, the increase in tensile strength with draw ratio gave evidence that hot drawing is more efficient in generating intercrystalline tie molecules than cold drawing.