| Brillouin light scattering is used to characterize the changes in the physical properties of solid, semicrystalline polymers which have been oriented by stretching or hydrostatic extrusion. The frequency shift and intensity of the scattered light is used to make precise measurements of the second velocities, elastic constants, and photoelastic constants of the polymer samples.;The Brillouin spectrum of oriented polymers is fully characterized. The photoelastic constants in extruded and stretched samples are measured and the changes in the Brillouin intensities with orientation are accounted for. The extra features observed in the spectra are assigned and the quantifying expressions for these are derived.;The polymers which are studied here include stretched films of poly(vinylidene fluoride), poly(ethylene terepthalate) and poly(chloro trifluoroethylene); and hydrostatically extruded poly(propylene) and poly(chlorotrifluoroethylene). Poly(ethylene terepthalate) was studied over a range of temperatures close to the glass transition.;The elastic constants, C(,11), C(,33), C(,13) and C(,44) for the various polymers are obtained from the sound velocity data by fitting it to the theory of elasticity for cylindrically symmetric solids. The stretching and extrusion processes produce distinctive trends in the elastic constants with deformation which are similar in the different polymers.;A model of affine deformation of a polymer solid is derived which relates the elastic constants to the degree of orientation of the constituent polymer chains. The model is used to qualitatively assess the morphology produced by the stretching and extrusion processes. |
