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 (Δα/3α₀) 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. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 33–44, 1998     

Opto‐thermal properties of fibers. XV. A study of the drawing behavior of quenched poly(ethyleneterephthalates) fibers

Studies of the mechanical and optical properties of undrawn uniaxially stretched polyester PET (Egyptian manufacture) fibers by annealing and cold drawing were performed. The optical properties and strain produced in PET fibers at different conditions were measured interferometrically at room temperature. A two‐beam interferometric technique was used to determine refractive indices and birefringence of the investigated PET samples with strain produced by different stresses. Using a microstrain 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, the number of molecules per unit volume, Poisson's ratio, the strain optical coefficient, and several other parameters and constants. Also, some structural parameters are determined, such as form birefringence, the virtual refractive index, the harmonic mean polarizability of the dielectric, the harmonic mean specific refractivity, and the isotropic refractive index. The generalized Lorentz–Lorenz equation given by de Vries is used to determine PET fiber structure parameters. Comparison between the results have been compared with Hermans' optical orientation function. 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. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1869–1880, 1999     

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. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:1955–1963, 1998     

Opto-mechanical properties of fibres. Part 1. Optical properties and orientation of drawn polyethylene fibres

Changes in the structure of different drawn polyethylene (PE) fibres are studied by the Becke' line method and interferometrically. The Becke' line method is used to study the changes in the optical properties of the skin layer of PE undrawn fibres. A Pluta polarizing interference microscope is used to determine the mean refractive indices and mean birefringence of the drawn fibres. Some structural parameters, such as optical orientation function, electric polarizability difference and isotropic polarizability (Δα/3α₀), are determined. This last parameter is found to be constant and depends only on the fibre structure. The number of molecules per unit volume and the distribution of segments at an angle with respect to the draw ratio are also determined. The generalized Lorentz–Lorenz equation given by de Vries is used to determine PE fibre structural parameters. A comparison between the experimental and those obtained using the Lorentz–Lorenz equation is given. A refractive index profile can assist fibre characterization. An empirical formula is suggested to correlate the changes in A, Δn, f_θ and θ with the draw ratio, and its constants are determined. Microinterferograms and curves are given for illustration. © 1999 Society of Chemical Industry     

Opto‐thermal properties of fibers: XVII. Structure characterization of cold drawn boiled viscose fibers

A two‐beam interferometric method is used to study the change of optical parameters of cold drawn boiled viscose fibers at different times. A stress–strain device conjugated to the Pluta polarizing interference microscope is used to investigate the dynamical behavior of opto‐mechanical properties at room temperature. Some structural parameters such as the number of molecules per unit volume, the virtual and isotropic refractive indices, the optical orientation factor and angle, the strain and the stress optical coefficients are evaluated. Some mechanical parameters such as, Young's modules, elastic shear modules and the compressibility are calculated over different strain values. Also the number of network chain per unit volume N_c, work per unit volume W, average work per chains W′, reduction in entropy ΔS, and the optical configuration parameter Δα are determined. Also calculation of the constants of Moony–Rivilin equation are given. A systematic study over different wavelengths range extending from 405 to 590 nm was carried out to obtain the dielectric constant at infinity. The obtained results clarify that new reorientations occurred due to cold drawing at different conditions. Empirical formula is suggested to correlate the change in Δn, f(θ), W, W′, A, θ, and N_c with different draw ratio, and its constants were determined. Microinterferograms and curves are given for illustrations. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1185–1201, 1999     

Opto‐thermal properties of fibers XVIII—Skin‐core structures variations in nylon 6 fibers due to different annealing conditions

Nylon 6 fibers (Amilan) were annealed at constant temperature 140 ± 1°C for different time durations (1–10 h). Refractive indices have been previously measured interferometerically. Two independent techniques were used to study the optical anisotropy and density in these fibers. The first was the application of a multiple‐beam to determine the skin and core “mean” refractive indices and birefringence of the samples. The technique used multiple‐beam Fizeau fringes in transmission. The second technique was an acoustic method for measuring the density of the investigated fibers. The optical results were used to calculate the optical orientation factors for skin and core. The values of (Δα/3α₀), which depend upon the molecular structure of the polymer, remain constant and in agreement with the previous published data. The density results were used to calculate the degree of crystallinity of nylon 6 fibers. In addition, the results were used to calculate the mean square density fluctuation, the harmonic mean polarizability of the dielectric, specific refractivity of the isotropic dielectric and the virtual refractive index. Also, the number of monomer units per unit volume, and n₁ and n₂, which are the refractive indices of fully oriented fiber, were calculated and found to be (1.606 and 1.534). Hermans optical orientation functions have been compared with the generalized Lorentz‐Lorenz equation given by de Vries. Microinterferograms and curves are given for illustration. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3349–3360, 2001     

Optomechanical variations in cold‐drawn thermally treated polypropylene fibers

A two‐beam polarizing interference microscope with a microstrain device was used for measuring some optical and mechanical parameters for polypropylene (PP) fibers at room temperature (28 ± 1°C). The changes in the molecular orientation were evaluated to obtain orientation factors f₂(θ), f₄(θ), f₆(θ), 〈P₂(cos θ)〉, 〈P₄(cos θ)〉, and crystalline and amorphous orientation functions F_c and F_a, respectively. The shrinkage factor, uniaxial tension, true stress, molar refractivity R, surface reflectivity R′, the crosslink density N_s, the chain entanglement density N_c, the segment anisotropy γ_s, and the number of chains N′ were calculated. In addition, the shrinkage stress was found to increase with the increase of draw ratio. The dielectric constant ε, the dielectric susceptibility η, the average work per chain w′, and the constants of the stress–birefringence equation were obtained. Comparison between Hermans's optical orientation functions and the corrected formulas by de Vries are given. The values of fully oriented refractive indices n₁ and n₂ were found. The generalized Lorentz–Lorenz equation given by de Vries was used to determine the structural parameters of PP fibers. An empirical formula was suggested to correlate the changes in the evaluated parameters with different draw ratios, and its constants were determined. The study demonstrated changes on the molecular orientation factors and evaluated microstructural parameters as a result of an applied cold‐drawing process. Relationships between the calculated parameters and the draw ratios, together with microinterferograms were presented for illustration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 729–738, 2003     

Optothermal properties of fiber morphology on nylon 66 fibers due to annealing and drawing processes

The changes produced by the effects of annealed and drawn fibers on the microstructure and macrostructure of nylon 66 fibers are considered. The optical properties and strain produced in nylon 66 fibers under different conditions are measured interferometrically at room temperature. Structural parameters are calculated such as the average work per chain, the work per unit volume, the reduction in entropy due to elongation, and the work stored in the body as strain energy. The evaluation of the density aided the calculation of the crystallinity, the mean square density fluctuation, the isotropic refractive index, the harmonic mean polarizability of the dielectric, and the harmonic mean specific refractivity. In addition, the resulting data are utilized to calculate the optical stress coefficient and the optical configuration and to apply the Mooney–Rivlin equation to determine its constants. Also, the number of crystals per unit volume and the average orientation angle for uniaxial stretching are calculated by the extension ratio. The relations between the optical, mechanical, and thermal changes with different parameters are given for the studied fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 916–928, 2002; DOI 10.1002/app.10107     

Changes in orientation caused by UV irradiation of nylon 6 fibers

The effect of UV radiation on the structural parameters that relate to the optical properties of nylon 6 fibers are investigated using interferometry. When the optical parameters are known, we can use them to calculate various orientation functions given by Hermans and de Vries. The properties of concern are the surface reflectivity, transparency, stress optical coefficient, stress due to UV irradiation, optical configuration parameter, segment anisotropy, dielectric constant, and susceptibility. The number of molecules per unit volume, isotropic refractive index, polarizability of a monomer unit, specific refractivity of the dielectric (along and across the fiber axis) and the form birefringence were obtained. The results are established by relationships designed to relate the calculated structural parameters to the time of exposure. The study demonstrates how the structural parameters change during exposure to UV radiation. Illustrations are given using graphs and microinterferograms. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3202–3211, 2003     

Optothermal properties of fibers: 12‐Interferometric investigation for thermally treated viscose fibers

The present article studies the structure of annealed viscose fibers interferometrically at a constant temperature of 100 ± 1°C at different times. The Pluta polarizing interference microscope has been used for determining the mean refractive indices and mean birefringence. The results were used to calculate the optical orientation function and the angle of orientation. The value (Δα/3α₀), which depends on the molecular structure of the polymer, remains constant. Relationships between the mean refractive indices, birefringence, isotopic refgractive index, and polarizabilities per unit volume with different times were given for these fibers. The samples were subjected to X‐ray diffraction to clarify the variation of crystallinity with the annealing conditions. Differential thermal analysis measurements were used to determine the glass transition temperature of viscose fiber. Measurements of the volume swelling parameter of the viscose fibers with different liquids were given. Also, determinations of Cauchy's constants, dispersive power, and dielectric constant at infinity were carried out. Illustrations are given using graphs and microinterferograms. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 361–369, 1999     

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 η², 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_a, and A with the draw ratio. Microinterferograms and curves are given for illustration. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 68: 1371–1386, 1998     

Optothermal properties of fibers. X. Temperature dependence of the skin—core structure of nylon-6 fibers

Refractive indices and birefringence for skin and core changes with annealing, produced by different annealing conditions in nylon-6 fibers, were measured interferometrically. Applications were carried out using multiple-beam Fizeau fringes in transmission to determine Cauchy's constants and dispersive coefficients for the fibers. The resulting data were used to calculate the polarizability per unit volume for each layer. By optical microscopy, the geometrical parameters of the fiber cross section were found. The effect of temperature and time of annealing on the refractive index and birefringence for each layer were also investigated. The relationships between temperature and time of annealing with the optical parameters were drawn. Illustrations are given using microinterferograms and curves. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 695–709, 1997     

Development of macrostructural effects of cold drawing on nylon 6 fibers

This work reports measurement of the molecular orientation by two techniques for nylon 6 fibers drawn at room temperature. The changes in the strain and optical parameters are used to obtain some macrostructural parameters to evaluate the cold‐drawing process values of the mechanical orientation functions, [P₂(cos θ)], [P₄(cos θ)], amorphous and crystalline orientation functions (F_c and F_a), and the molar number of chain segments per unit volume (N_e). Also the crosslink density (N₀), the chain entanglement density (N_s), the average optical orientation F_av, the dielectric constant (ε), the dielectric susceptibility (η), the shrinkage stress (k_s), and other parameters were calculated. Relationships between the calculated parameters are given. The present study demonstrates changes in the molecular reorientation factors and the obtained new physical properties resulting from cold‐drawing process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 287–295, 2004     

Study of Optical and Structure Properties of Polyester (PET) and Copolyester (PETG) Fibers by Interferometry

In this article results on the influence of drawing on the optical and structure properties of polyester (polyethylene terephthalate) and copolyester (glycol-modified polyethylene terephthalate) (4 wt% of ethylene glycol) fibers are reported. Refractive indices, intrinsic birefringence, mean polarizability per unit volume, optical orientation function, density, volume fraction of crystalline material, weight fraction crystallinity, and volume fraction of amorphous and work per chain of these fibers have been evaluated at different draw ratios. A comparison of optical and structure parameters for copolyester fiber and referenced monopolyester fiber has been done. This study has been carried out by means of computerized double-refracting Pluta interference microscope combined with opto-mechanical devices. Microinterferograms and relationships between the parameters obtained are given for illustration.     

Interferometric determination of the physical properties of annealed isotactic polypropylene fibers

Automated variable wavelength interference microscope was used to study the effect of annealing process on the physical properties of isotactic polypropylene fibers (4:1 draw ratio, 515 tex, Bolton UK). The isotactic polypropylene (iPP) fibers were annealed at temperatures ranging from 60°C to 140°C. The spectral dispersion curves of refractive indices and birefringence of iPP fibers were determined at different annealing temperatures. The resulting data were used to determine the optical orientation function, orientation angle, degree of crystallinity, and dispersion parameters of the annealed samples. The study indicates that, the measured birefringence, orientation function, and the dispersion of crystallinity of iPP fibers have been improved with the increasing of annealing temperature. POLYM. ENG. SCI., 59:35–41, 2019. © 2018 Society of Plastics Engineers     

Determination of optical properties,dispersion, and structural parameters of poly(ethylene terephthalate) fibers using automatic variable wavelength interferometry technique

Automatic variable wavelength interferometry (VAWI) is used in combination with a Pluta double refracting polarizing interference microscope for measuring the spectral dispersion parameters of the refractive indices of poly(ethylene terephthalate) (PET) highly oriented yarn fibers (1000 denier/250 filaments). The resulting data are utilized to calculate the spectral dispersion and structural parameters such as Cauchy's constants, the dispersion energy, the oscillation energy, the density, the mean polarizability of the monomer unit, the number of monomer units per unit volume, the dielectric constant, the electric susceptibility, the optical orientation function, and the electric polarizability constant. Microinterferograms are given for illustration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1737–1742, 2003     

Influence of creep on optical properties of polypropylene fibers

The change in some optical properties with the creep extension is measured for polypropylene fibers at several constant applied loads. Multiple-beam Fizeau fringes in transmission are used to determine the mean refractive indices and the mean birefringence of these fibers at different values of creep extensions. Also, the effect of creep extension on the birefringence profile of the fiber is studied. The creep-extension dependence of these optical properties for polypropylene fibers is demonstrated using a stress–strain device connected to a wedge interferometer where the fiber is subjected to a constant load. The results show that under constant load the fiber will extend with time at a rate which decreases as time increases. An empirical formula is suggested to represent the variation of creep extension (%) of polypropylene fibers with time in the time interval of 0–55 min and the constants of this formula are determined. Microinterferograms are given for illustration. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 621–627, 1998     

Contribution of interferometry and mechanical parameters in evaluating molecular orientation for drawn polyester

Mechanical and structural parameters related to the optical properties of polyester (PET) (woollen type) fibres drawn at room temperature have been investigated. The changes in the strain were evaluated to obtain the molecular orientation factors 〈P₂(cos θ)〉 and 〈P₄(cos θ)〉. From the optical orientation, the values of f₂(θ), f₄(θ) and f₆(θ) orientation parameters were calculated. The structure and properties of oriented PET have been studied in the light of the rubber elasticity theory. The dielectric constant, magnetic susceptibility, number N′ of chains between crosslinks per unit volume, optical configuration parameter and the segment anisotropy, were among the calculated parameters. The results of the extension were used to calculate the shrinkage factor. Relationships between the calculated parameters and the draw ratios, together with micro-interferograms, are given for illustration. The present study throws light on how the applied stress changes the molecular orientation factors and the structural parameters. © 1999 Society of Chemical Industry     

The effect of stretching on monofilament polypropylene sutures

The effect of cold drawing on monofilament Polypropylene sutures PP at room temperature 24 °C were studied interferometrically. The changes in the molecular orientation were evaluated to obtain optical and mechanical orientation factors f ₂(θ), f ₄(θ), f ₆(θ), P ₂(cosθ), P ₄(cosθ), crystalline and amorphous orientation functions F _c and F _a, respectively. The shrinkage factors, the reduced stress and the number of chains between cross links per unit volume were determined. Calculation of the cross link density (N ₀) and the chain entanglement density (N _c) with the aid of Moony–Rivlin equation constants were given. Also, other various different opto-mechanical parameters were calculated. Relations between the optical and mechanical parameters were given. The present study demonstrates changes in the different orientation factors and structural parameters. Illustrations were given using curves and microinterferograms.     

Birefringence and orientation parameters of cold‐drawn viscose fibers

This study was carried out by two beam polarizing interference Pluta microscope to obtain changes undrawn viscose fibers. Application of the appropriate mathematical equations indicates that the refractive indices in the direction of the drawing force increase with increasing the draw ratio and decrease in the perpendicular direction. The changes in the draw ratio were evaluated to obtain the shrinkage stress, the mechanical function factors 〈P₂(cos θ)〉 and 〈P₄(cos θ)〉, the average work per chain W′ for a collection of chains, and the average mechanical orientation. The optical results were to obtain the three optical orientation functions, the dielectric constant and the dielectric susceptibility and the average orientation function. Also calculation of the intrinsic crystalline and amorphous birefringence. Evaluation of another opto‐mechanical parameters were given, too. An empirical formula was suggested to evaluate the relationship between the draw ratio and some determined opto mechanical parameters. Illustrations using microinterferogram, graphs, and tables are given. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007