Microinterferometric Studies On Fibrous Materials

Abstract

Two-beam and multiple-beam microinterferometric methods have been used in studying and analyzing polymer fibres. These techniques are ideally suited for measuring refractive in-dices and birefringence of these fibres. Multiple-beam Fizeau fringes in transmission and at reflection were used to investigate the optical properties of layers of fibres with irregular transverse sections having a skin-core structure. The area enclosed under the interference fringe shift was considered to represent the path difference across the fibre. Cylindrical multi-layer fibres were also studied interferometrically. Information about the molecular orientation and some structural parameters of fibres are available using interferometric techniques. The change of optical anisotropy of fibres due to γ-irradiation has been investigated and was suggested to develop a simple method for γ-ray dosimetry. The effect of drawing the fibres on their optical orientation function has been studied interferometrically. Refractive indices and birefringence changes with strain produced by different stresses in undrawn fibres have been measured dynamically by interferometry using a device connected to the wedge interferometer. A fibre manipulation device was designed, constructed and used to study the dependence of birefringence on strain in case of polymer fibres. This device was used with the Pluta polarizing interference microscope to determine the refractive indices and birefringence under strain. It enables one to study stretched, twisted and rotated fibres and can be fitted easily to the interference microscope. Microinterferograms are given for illustration.