Orientation relationship and mechanical properties of rolled polypropylene sheets

The orientation structure in rolled polypropylene was observed by scanning electron microscopy (SEM). The tensile properties of rolled polypropylene sheets with different reduction ratios in thickness were monitored. Wide-angle X-ray diffraction (WAXD) measurements of the orientation distribution of (hkl) crystal planes gave values of the even order <P-n(cos chi)>(c) coefficients of the Legendre polynomial series, which characterize the c-axis or orientation distribution of the molecular chains. According to the non-linear viscoelastic theory for large deformation of polyolefine, the coefficient C-200 in the stress-strain relationship was related to the aligned polymer chain along the elongation direction. A linear relationship is found between the modulus E and the orientation distribution q(chi) and is verified by the experiment results.