Measurements of the photoelastic and elastic constants of drawn films and extruded rods of polypropylene with Brillouin light scattering

摘要

The elastic constants C11, C33, C44, C13 of oriented poly propylene films are measured with Brillouin scattering and are compared with the elastic constants obtained from extruded poly propylene rods. The photoelastic constants p12, p13, and p31 of the extruded rod samples are measured by comparison to a poly(methylmethacrylate) reference scatterer. In the film samples, the relative values of the photoelastic constants p11, p33, p13, and p31 are measured by comparison of the quasilongitudinal and quasitransverse intensities at several directions of sound propagation. Within the experimental error, p13, p31, and p12 are found to be unaffected by extrusion or stretching. p11 and p33 are found to change in relation to p31 in the film samples. The results are interpreted by considering the chain morphology and the theory of photoelastic interaction. The changes in the Brillouin intensities are due to changes in the elastic constants, rather than the photoelastic constants.