Very high modulus high-density polyethylene and high-modulus polypropylene obtained by solid-state roll drawing

This article describes results obtained with a process developed for rolling and drawing simultaneously polymer profiles in the solid state. Solid-state roll drawing has the advantage of being continuous, which allows relatively high production rates and the generation of high deformation ratios with some degree of biaxial orientation. The roll-drawing process allows the extent of biaxial orientation to be controlled by the adjustment of the tension and compression loads applied to the polymers, in particular semicrystalline thermoplastics. Some experimental results obtained with a four-station roll-drawing apparatus are presented, particularly on high-density polyethylene (HDPE) and polypropylene. The effect of process parameters, such as the gap between the rolls and tension, are discussed. Aspects discussed also include relaxation; structure development in terms of orientation and crystallinity as a function of draw ratio (\u3bb); \u3bb as a function of process parameters; and finally, mechanical and thermal properties as a function of \u3bb. Moduli as high as 25 GPa in the longitudinal direction and about 4 GPa in the transverse direction were obtained with successively rolled, initially thick, HDPE profiles.Peer reviewed: YesNRC publication: Ye