Optical anisotropy in oriented polyvinyl chloride

This paper reports measurements of the variations of residual optical birefringence and extinction direction with residual strain occurring in tensile test pieces cut from oriented polyvinyl chloride strip and extended in simple tension. The strips were oriented by prior extension and both the degree of orientation and the angle between the orientation direction of the strips and the direction of subsequent extension of the test pieces were varied. The experimental results are discussed in terms of a molecular orientation model due to Kuhn and Grün and developed in this paper to apply to cases such as described here, in which the transverse contraction accompanying the longitudinal extension of the test pieces is anisotropic. Agreement between experiment and theory is reasonable in view of the simple assumptions made.