Effect of the Chain Alignment on the Brillouin Scattering Spectra of Hydrostatically Extruded Polypropylene.
UTAH UNIV SALT LAKE CITY DEPT OF CHEMISTRY
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A detailed Brillouin scattering study of hydrostatically extruded polypropylene at room temperature is carried out. The spectra obtained in various scattering configurations are used to determine the hypersonic velocity and elastic constants of the uniaxially deformed polycrystalline polymer. As polypropylene is extruded, C33 increases rapidly with increasing extrusion, whereas C11 decreases slightly. This result reflects the increasing alignment of the polymer chain segment along the direction of extrusion. The elastic constant C13 decreases slightly, but C44 does not undergo significant change as the sample is extruded, thus indicating that the shear modulus is insensitive to the orientation of chain segments in polycrystalline polypropylene. Comparison of the Brillouin scattering results with the ultrasonic values indicate that considerable frequency dispersion in the elastic constants is present. Calculation of the orientation parameter using Moselys theory does not yield correct results. The discrepancy indicates that Moselys model should be used with care. Author
- Atomic and Molecular Physics and Spectroscopy