Determination of the orientation in poly(ethylene terephthalate) films by comparison of birefringence and X‐ray diffraction

Abstract

AbstractThe interpretation of the birefringence of biaxially drawn poly(ethylene terephthalate) is rather difficult because of its complicated and non‐unique relation to the orientation. Moreover, crystalline and amorphous parts of the material assume different degrees of orientation and have often different directions of the principal axes of orientation. These relations, including the influence of different texture components, are analyzed theoretically and estimated experimentally by comparison with the orientation parameters found by X‐ray diffraction.