Henry Kobsa

Using Optical Ray Tracing to Explain the Reduced Dye Yield of Microdenier Yarns

An optical ray trace luster prediction computer model is used to explain the reduced dye yield of microdenier yarns. Results from the model demonstrate that the reduced dye yield is a necessary consequence of the reduced path length of light inside the filaments. Data are shown for the predicted brightness of a set of standard denier per filament and microdenier PET ( Micromattique ) yarns.

Modeling the Dependence of Fabric Reflectance on Denier per Filament

A ray trace model for predicting fiber optical properties has been previously described. This model, which treats each filament in a yarn bundle independently, has been extended to include multifilament scattering. The new model is used to predict the reflectance properties of a series of simulated yarn bundles with different numbers of filaments, providing further insight into the interaction of light with a fabric. Two effects of reducing denier per filament are predicted: decreased dye yield and increased back-scattering. The dye yield data are in agreement with the empirical relationship that the amount of dye required to achieve a given depth of shade varies as the inverse square root of the denier per filament.

Investigating the Structure of Nylon Fibers by Measuring the Diffusion Coefficient of Acid Dyes Part III: The Effect of Heatsetting on Nylon 66 Fibers

The diffusion coefficient of CI acid blue 40 at 25°C was measured in samples of a nylon BCF carpet yam that had been heatset at 100% RH at temperatures ranging from 30 to 170°C. The diffusion coefficient at first dropped modestly as the heatsetting temperature increased, went through a shallow minimum, and then rose exponentially several orders of magnitude as the melting point of the yam was approached. Some speculations about the structural changes responsible for this behavior are offered.

Investigating the Structure of Nylon Fibers by Measuring the Diffusion Coefficient of Acid Dyes: Part I: A Semi-Empirical, Approximate Solution to the Diffusion Equation

A semi-empirical solution of the diffusion equation is proposed for dyeing fibers with round cross sections from finite dye baths with soluble dyes whose adsorption isotherm is of the Langmuir type. This solution is valid during the early part of the dyeing cycle until about 45% of the dye has been exhausted. A method is described for measuring dyeing rates, which can be used to calculate diffusion coefficients. This method of determining diffusion coefficients is much faster than other methods described in the literature.

Application of CO laser for frequency selective surface heat treatment of polymer materials

Frequency selected Q-switched e-beam controlled-discharge CO- laser has been researched and developed for surface heat treatment of polymeric materials [poly(ethyleneterephthalate) and nylon] having strong absorption bands near wavelength of approximately 6 micrometer. The laser generates pulses (including short ones with duration (tau) 0.1 approximately 1 - 10 microsecond(s) ) having different spectral content within 4.9 - 6.5 micrometer spectral range. Different geometry and methods of irradiation were used to process samples with the laser radiation of different temporal, spectral and energy density characteristics. Different types of microstructure were formed on the surfaces of the samples. Experimental conditions corresponding to each type of microstructure were defined. Visual (macro) changes of polymeric material properties (if any) and their correlation with formed microstructures were analyzed.

Irradiation of fabrics of nylon and poly(ethylene terephthalate) with short frequency-selected pulses from CO 2 , and CO, eximer lasers

Using excimer lasers in DuPonts laboratories in Wilmington, we showed that a wide variety of nylon and polyester fabrics can be successfully irradiated to produce fabrics which combine the attractive visual and tactile aesthetics of cotton or wool fabrics with the durability, wrinkle resistance, and wash-and-wear performance of fabrics of 100 percent nylon or polyester. Extensive wear tests in such demanding end uses as bicycle pants proved that the desired aesthetic improvements were retained in use.

Part II: Generalization of the Solution to Arbitrary Cross Sections

The semi-empirical solution to the diffusion equation for the case of dyeing fibers with round cross section from finite baths containing soluble dyes proposed in the first paper of this series is generalized to fibers of arbitrary cross section. The errors incurred by this generalization are examined and correction factors are given.

Frequency-selected Q-switched e-beam-controlled discharge CO laser and its applications

Frequency selected Q-switched e-beam controlled-discharge CO-laser has been researched and developed for surface heat treatment of polymeric materials (poly(ethyleneterephthalate) and nylon) having strong absorption bands near wavelength of approximately 6 micrometers . The laser generates pulses (including short ones with duration (tau) 0.1 approximately 1 - 10 microsecond(s) ) having different spectral content within 4.9 - 6.5 micrometers spectral range. Different geometry and methods of irradiation were used to process samples with the laser radiation of different temporal, spectral and energy density characteristics. Different types of microstructure were formed on the surfaces of the sample. Experimental conditions corresponding to each type of microstructure were defined. Visual (macro) changes of polymeric material properties (if any) and their correlation with formed microstructures were analyzed.

Frequency-selected surface heat treatment of polymeric materials by pulsed CO laser radiation

Frequency selected pulsed CO laser was used for surface heat treatment of polymeric materials. Nylon and poly(ethyleneterephthalate) samples having strong absorption bands near wavelength of approximately 6 micrometers were processed by the laser radiation of different temporal, spectral and energy density characteristics by using different geometry and methods of irradiation. Different types of microstructure were formed on the surfaces of the samples. Experimental conditions corresponding to each type of microstructure were defined. Visual (macro) changes of polymeric material properties (if any) and their correlation with formed microstructures were analyzed.

Application of pulsed CO laser for surface heating treatment of nylon and poly(ethyleneterephthalate) fabrics

Frequency selected Q-switched e-beam controlled-discharge CO-laser has been researched and developed for surface heat treatment of polymeric materials (poly(ethyleneterephthalate) and nylon) having strong absorption bands near wavelength of approximately 6 micrometers . The laser generates pulses (including short ones with duration of (tau) 0.1 approximately 1 - 10 microsecond(s) ) having different spectral content within 4.9 - 6.5 micrometers spectral range. Different geometry and methods of irradiation were used to process samples with the laser radiation of different temporal, spectral and energy density characteristics. Various types of microstructure were formed on the surfaces of the samples. Experimental conditions corresponding to each type of microstructure were defined. Visual (macro) changes of polymeric material properties (if any) and their correlation with formed microstructures were analyzed.