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Interferometric determination of (skin-core) optical and orientation structural parameters of drawn polypropylene fibres

Multiple-beam Fizeau fringes in transmission were used to study the changes of the principal optical properties of six samples of drawn polypropylene fibres. The resulting data of the mean, skin and core refractive indices and birefringence of these fibres were used to calculate some structural parameters such as the optical orientation function, orientation angle, the isotropic refractive index, the virtual refractive index, the number of molecules per unit volume and the random links per chain. Poisson's ratio and the strain optical coefficient are also determined. The distribution of segments at an angle with respect to the draw ratio and the electric polarizability constant (Δα/3α0) and other parameters and constants are determined. The generalized Lorentz-Lorenz equation given by de Vries has been used to compare the results obtained by Herman's optical orientation function. Microinterferograms, tables and graphs are given for illustration.