Melt flow crystallization of ultrahigh molecular weight polyethylene under curvilinear flow conditions

Multiaxially oriented ultrahigh molecular weight polyethylene films were prepared recently under curvilinear flow conditions generated by the combined effects of compression and rotation. The films were prepared by melt flow crystallization in an optical apparatus specially designed for rheo‐optical observations. Morphological studies indicate that the films were fibrillar with the fibrils oriented along the circular flow lines. The fibrils were lamellar, and their lamellar thickness (150–450 Å) and spacing (400–2000 Å) depended on the processing conditions. The film exhibited strong birefringence (1.4 × 10−2) and had a Young modulus of 15–25 GPa along the flow lines and 3–5 GPa in the transverse direction.