Title: Form Birefringence Effect of Ultradrawn Polyethylene Determined by Two Dimensional Composite Structural Model
Abstract: Birefringence was calculated as a function of the content of voids, φ, assuming that the morphology of ultradrawn polyethylene film is represented by a composite model. When birefringence is calculated using a parallel model, it is beyond 60×10−3 at φ≥0.24. This indicates that the birefringence >60×10−3 observed for ultradrawn polyethylene films is attributed to the contribution of form birefringence. The theoretical calculation indicates that the real birefringence without contribution from form birefringence cannot be obtained by Wiener’s method, since the maximum or minimum point of birefringence curve against refractive index of swelling liquid is not equal to the real birefringence.