Two-beam interference detection of the changes in fibre structural parameters during low drawing process

A Pluta polarizing interference microscope with a fibre stretching device attached was used to detect the changes in molecular structure that occur during the fibre cold drawing process. Fibres drawn with low draw ratios show different types of deformation mechanisms. The interference patterns recorded at different draw ratios are used to relate the deformation mechanisms with the measured structural parameters. Some optical parameters are measured such as; refractive indices nand n birefringence n, the polarizability per unit volume , the orientation distribution function f(θ), the angle θ between the stretching direction and the chain axis, and the angle θ_m which the transition dipole moment of the molecular species makes with the molecular axis (chain axis). Three polymeric fibres (Polyethylene terephthalate PET, Polypropylene PP and Polyamide PA) were used in this study and their interferograms are illustrated.