Structural Formation of UHMWPE Film Tracked by Real-Time Retardation Measurements during Uniaxial/Biaxial Stretching

This work reports on an experimental study of the stretching of ultra-high molecular weight polyethylene (UHMWPE) film in various uniaxial/biaxial stretching modes at various temperatures and stretching speeds. We examined the stress-birefringence relationship as a stress-optical rule (SOR) under uniaxial stretching and evaluated the stress-optical coefficient (SOC). Wide-angle X-ray diffraction (WAXD) measurements were applied to evaluate the contribution to birefringence of the crystalline and amorphous phases and to characterize stretching modes. In simultaneous biaxial stretching, the melting temperature (T(m)) proved critical to structural formation. We applied thermal analysis techniques and tensile testing to evaluate higher order structures after each stretching mode.