F. M. El-Sharkawy

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.

Optothermal properties of fibers. VI. Effect of annealing on some of the optical and dynamic mechanical parameters of polyester fibers

Changes in the structure of annealed polyester fibers (Egyptian manufacture) at a constant time of 5 h and different temperatures (80-190°C) were studied interferometrically. The Pulta polarizing interference microscope was used for determining the mean refractive indices and mean birefringence of these fibers. The multiple-beam Fizeau fringes in transmission was also used for determining the refractive indices of the skin and core of these fibers. Also, the acoustic method was used for measuring the density and mechanical loss factor of these fibers. Relations between the mean refractive indices, birefringences polarizabilities per unit volume, and mechanical parameters of annealed polyester fibers with different temperatures are discussed to clarify the thermal effects. Illustrations are given using graphs and microinterferograms.

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. II. Annealing effect on the birefringence variations of polyester fibers

The variation of refractive indices and birefringences of Egyptian-manufactured polyester fibers with different annealing times at constant temperature 160°C are studied by interferometry. The polarizing interference microscope is used for determining the mean refractive indices and mean birefringence of these fibers. The results are used to calculate optical orientation function and the angle of orientation. Also, the acoustic method has been used for measuring the density and the mechanical loss factor of these fibers. Relations between the mean refractive indices, birefringence, polarizabilities, mechanical loss factors, and densities with annealing time are given for these fibers. Illustrations are given using graphs and microinterferograms.

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-thermal properties of fibers. XVI. Macrostructural and optical properties of cold-drawn, quenched PET fibers

In this article, the relation between the macrostructural changes in uniaxially stretched polyester (PET) fibers, caused by heat treatment, and quenched in coarse-grain ice were studied. The developing macrostructure was determined using double-beam interferometry. Application was carried out by two-beam interferometry to determine the optical parameters. Using a two-beam Pluta polarizing interference microscope connected to a device to dynamically study the draw ratio with birefringence changes. The relations of drawing changes with some optical parameters are given. The evaluation of density, the mean square density fluctuation, crystallinity, amorphous orientation, crystalline orientation functions, the mean square density fluctuation (η 2 ), the number of chains per unit volume N c , and the number of random links between the network junction points N (1) have been found. The results obtained clarify the effect of annealing time and temperature with different draw ratios on the structure of PET fibers. Also, the optical results were used to calculate an optical orientation function and an optical orientation angle of drawn, quenched PET fibers. Relations between the optical data, draw ratios, and other parameters with different quenching conditions are given for these fibers. The change of the refractive index profile of the quenched PET fibers with various conditions are given. Illustrations are given using graphs and microinterferograms.

Optothermal properties of fibers. XIV. Investigation of some optical structural parameters of annealed and cold drawn polyester fibers

Two-beam interferometry and density methods previously measured are used to study the changes in optical properties of annealed and cold drawn polyester (PET) fibers. Some structural parameters in the present work are determined, such as form birefringence, the number of molecules per unit volume, the virtual refractive index, the harmonic mean polarizability of the dielectric, the harmonic mean specific refractivity, and the isotropic refractive index. Also, the distribution of segment at an angle with respect to the draw ratio and the electric polarizability constant (Δa/3α o ) are determined. The generalized Lorentz-Lorenz equation given by de Vries is used to determine PET fiber structure parameters. Comparison between the results have been made with the Hermans optical orientation function.

Opto-thermal properties of fibers. XI. The effect of thermal annealing of drawing behavior for egyptian polyester fibers on the crystallinity and some optical parameters

The structure developed of annealed Egyptain poly( ethyleneterephthalate ) (PET) fibers is studied interferometerically due to the drawing process. Using a two-beam Pluta polarizing interference microscope connected to a device to dynamically study the draw ratio with the birefringence changes, the relations of drawing changes with some optical parameters are given. The evaluation of density, the mean square density fluctuation (η 2 ), crystallinity, amorphous orientation, crystalline orientation functions, number of chains per unit volume N c , and number of random links between the network junction points N has been found. The results obtained clarify the effect of annealing time and temperature with different draw ratios on the structure of PET fibers. Empirical formula is suggested to correlate the changes in f θ , θ, Δn α , and A with the draw ratio. Microinterferograms and curves are given for illustration.

Optothermal properties of fibers. XIII. Evaluation of the form birefringence and some other structural parameters due to thermal annealing for polyester (PET) fibers

In this work, changes in the structure of polyester [poly(ethylene-terephtalate)(PET)] fibers after annealing at constant temperature ( 120 and 140°C) and different times were studied interferometrically. The density of annealed PET fibers were measured by a system based on vibrating string. The Pluta polarizing interference microscope was used to determine the optical parameters of these fibers. The density and optical results were used to calculate the degree of crystallinity, the form birefringence, the number of monomeric units per unit volume, harmonic mean polarizability of the dielectric, harmonic mean specific refractivity, and the virtual refractive index. The behavior of fiber crystallinity at different annealing conditions were discussed with different optical parameters. Hermans optical orientation function have been compared with the generalized Lorentz-Loranz equation given by de Vries. Microinterferograms and curves are given for illustration.