M. A. Kabeel

Multiple-beam interferometric studies on fibres with irregular transverse sections

An analysis of multiple-beam Fizeau fringes crossing fibres with irregular transverse sections is given. The area enclosed under the fringe shift is considered to represent the path difference integrated across the fibre. The method is applied to the determination of refractive indicies and birefringence of dralon fibres. Microinterferograms are given for illustration.

Interferometric determination of optical properties of fibres with irregular transverse sections and having a skin-core structure

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. Mathematical expressions have been derived for the values of refractive indices and birefringence of these fibres. These expressions were applied to determine the optical properties of two samples of nylon-6 fibres.

Multiple-beam Fizeau fringes crossing a cylindrical multi-layer fibre

Mathematical expressions are derived for the shape of multiple-beam Fizeau fringes crossing a cylindrical multi-layer fibre. The area enclosed by the deviation of the interference fringe as it crosses the fibre is considered to represent the path difference integrated across the fibre. This interferometric method is applied to determine the refractive indices and birefringence of each layer of polypropylene fibres.

Optical anisotropy in polypropylene fibres as a function of the draw ratio

In this work optical properties of six samples of polypropylene fibres having different draw ratios are measured interferometrically using multiple-beam Fizeau fringes in transmission. These fibres are found to show considerable optical anisotropy. Three independent techniques have been employed to study the optical anisotropy in these fibres. The first technique determined the geometrical parameters of the fibre from its diffraction pattern using a He-Ne laser beam at 632.8 nm. The second is the application of the Becke-line method to determine the refractive indices and birefringence of the fibres skin. The third is the application of multiple-beam Fizeau fringes in transmission to determine the mean refractive indices and the mean birefringence of these fibres with different draw ratio. The refractive index of the fibres core is calculated from the predetermined parameters. Relationships between the mean refractive index and the birefringence of fibres with the draw ratio are given and illustrations with microinterferograms are presented.

The optical behaviour of polyethylene fibres with different draw ratios

Abstract Seven samples of polyethylene fibres with different draw ratios were studied by means of the measurement of their refractive indices and birefringence. In this study three independent techniques were used. These techniques were the Becke line, two-beam and multiple-beam Fizeau fringes. Variation of refractive index of the fibre with temperature was determined for two different draw ratios. Applications were carried out in which multiple-beam Fizeau fringes in transmission were used to determine the constants of Cauchys dispersion formula. The resulting data were utilized to calculate the polarizability per unit volume of the fibre material. Relationships between the optical parameters and the draw ratios are given. The results obtained clarify the effect of the draw ratio on the optical behaviour of polyethylene fibres. Microinterferograms are given for illustration.

Opto-Mechanical properties of fibres. 7: Relation between cold Drawing behaviour of nylon 6 fibres from an Egyptian manufacturer and their optical properties

Optical properties change with strain produced by different stresses. Undrawn Nylon 6 fibres from an Egyptian manufacturer have been measured dynamically by interferometry. Both two- and multiple-beam interferometric techniques were used to determine refractive indices and birefringence of the investigated Nylon 6 samples with strain produced by different stresses. Using a micro-strain device attached to a microscope stage and through the application of the appropriate mathematical equations, the refractive indices and the birefringence values were determined as a function of the draw ratios. The resulting data were utilized to calculate the polarizability per unit volume, Poissons ratio, the strain optical coefficient, and several other parameters and constants. Relationships between the various optical parameters and the draw ratios are plotted and the effect of draw ratio on the refractive index profile is studied. Microinterferograms are given for illustration.

1‐Opto‐thermal properties of fibers annealing effect on the birefringence variations of polyester fibers

Polyester (Egyptian) fibers were annealed at constant temperature (190°C) with different annealing times. Density, crystallinity, mean square density fluctuation, mechanical loss factor, and molecular orientation were calculated. Densities and mechanical loss factor were determined using an acoustic method. Changes in the molecular orientation were evaluated from the resulting optical data using the polarizing Pluta interference microscope. Correlation of data obtained by one method with another leads to relational changes in optothermal properties and in the molecular orientation. Changes of refractive index profiles of annealed PET fibers are provided. Illustrations using graphs and microinterferograms are shown.

Opto-thermal properties of fibers — 2. Structural characteristics of cold drawn annealed Egyptian polyester (PET) fibers

Abstract Egyptian poly(ethyleneterephthalate) (PET) fibers in the drawn state show considerable optical and mechanical anlsotropy. The polarizing interference microscope is used with a fiber manipulation device to study, dynamically, the variation of refractive indices and birefringence of PET fibers with the draw ratio. In addition, the resulting data were used to calculate the strain optical coefficient, Poissons ratio, the mean square density fluctuation under different annealing conditions, as well as several other parameters and constants. Also, an empirical formula has been applied to demonstrate the variation of the cross-sectional area of PET fibers with draw ratio and the constants of this formula are determined. Microinterferograms are given for illustration. The change of refractive index profile of annealed PET fibers at different conditions are also shown.

Optothermal properties of fibers. VIII. Structure orientation study of annealed Egyptian polyester fibers

A two-beam interferometric method is used to study the change of optical orientation functions and the molecular structure of annealed Egyptian poly(ethylene terephthalate)(PET) fibers. The acoustic method was used for measuring the density. The density results were used to calculate the degree of crystallinity of PET. It was found that annealing causes alignment to the fiber chains in the directions of the fiber axis. This alignment gives an increase in the optical orientation function and decrease in orientation angle. The value of Δα/3α 0 , which depends upon the molecular structure of the polymer, remains constant. The obtained results of the optical and the density clarify that new reorientations occurred due to annealing at different conditions. The changes of the refractive index profile of annealed PET fibers are given. Microinterfero-grams and curves are given for illustration.

Opto-mechanical properties of fibres. 6. Structural characteristics and optical properties of PE fibres

The polarizing interference microscope is used with a fibre manipulation device to study, dynamically, the variation of refractive indices and birefringence of PE fibres with the draw ratio. The resulting data were used to calculate Poissons ratio over all strain ranges. In addition, the strain optical coefficient and some other parameters and constants were calculated. Also, an empirical formula is applied to demonstrate the variation of the cross-sectional area of PE fibres with draw ratio and the constants of this formula are determined. Microinterfrograms are given for illustration.