Extrusion of self‐reinforced polyethylene

Abstract

AbstractIn recent years, efforts aimed at producing high‐strength polymers have intensified noticeably. In addition to additive‐based reinforcement, self‐reinforcement without additives represents a way to increase material strength. In this study, the effects of self‐reinforced polyethylene during extrusion with a conventional single‐screw extruder are investigated. High extrusion pressure and controlled flow conditions at a low stock temperature, in conjunction with a longitudinal flow gradient in the die, permit the production of high‐strength, extremely rigid profiles from high‐density polyethylene (HDPE). The reinforcement is due to the shish‐kebab structure, which is responsible for the improvement of thermal and mechanical properties. The growth of shish‐kebab structures with an extended chain crystal axis and the radially lamellar structure, originated by flow‐induced crystallization, depends on the orientation of the macromolecules in the melt. Compared to a conventional extruded profile, the high‐strength profile exhibits molecular chain orientation largely parallel to the direction of extrusion, homogeneous transparency, and an approximately tenfold increase in Young's modulus, as well as improved thermal properties and good dimensional stability.