Microscopic Deformation Process in Poly(4-methylpentene-1) under Uniaxial Tensile Stress

Abstract

Brillouin scattering (BS) and small and wide angle X-ray scattering (SAXS and WAXS) experiments were conducted on poly(4-methylpentene-1) over a wide temperature range from 16 to 85°C to investigate the microscopic deformation process in semi-crystalline polymers. It was clarified that application of uniaxial tensile stress, submicrocracks were generated in an amorphous region, resulting in a decrease in the elastic modulus along the tensile direction. The concentration of submicrocracks depended greatly on the strain level and testing temperature. It was particularly noted that submicrocracks were formed even above the glass transition temperture (Tg). This implies that the molecular motion in the amorphous region above Tg is partially restricted by the presence of the crystalline region. WAXS experiments showed that, with increasing applied strain, the strain of the crystal lattice increased at an initial stage, and then decreased slightly when a rapid increase in the submicrocracks concentration occurred. These results suggest that the microscopic deformation in semi-crystalline polymers proceeds under the mutual influence of and intimate correlation between the amorphous and crystalline phases.