Crystalline Orientation and Mechanical Properties with Biaxially Stretching of Ultrahigh Molecular Weight Polyethylene and Low Molecular Weight Polypropylene Blend Gel Films

I. Orientation Behaviors of Each Diffractive Plane and Mechanical Properties for Simultaneous Biaxial Stretching of Gel Press and Press Films

Abstract

Homo polyethylene and polyethylene-polypropylene blends were produced by gelation/crystallization from semidilute solutions using ultrahigh molecular weight polyethylene (UHMWPE) (2.0×10⁶) and low molecular weight high crystallinity polypropylene (it-PP) (4×10⁵). Homo it-PP film was produced by compression molding. Blend composition chosen were 75/25, 50/50, and 25/75. Homo PE and blend films were pressed using a molding machine in order to gain uniform thickness gelation films. Biaxial films, typically 2×2 and 3×3 times (for it-PP, 3×3 and 5×5 times) the original dimensions, were prepared at 130∼160°C in a biaxial stretcher. WAXD photographs show that lamellar structure transforms to fibrillar texture during biaxial stretching. The preferential orientations of the crystals were characterized by WAXD photographs. Mechanical studies suggest that tensile modulus and strength appear uniform. In comparison with undeformed film, significant improvement in the film plane was seen in the biaxially stretched film.