Boong Soo Jeon

CHARACTERISTICS OF ELECTRICALLY CONDUCTING POLYMER-COATED TEXTILES

Intrinsically conducting polymer (ICP)/textile composites were prepared by coating polypyrrole (PPy) or poly (3,4-ethylenedioxythiopene) (PEDOT) on the fabrics through chemical and electrochemical oxidation of pyrrole or EDOT. We investigated the effects of the preparation conditions on the properties of the resulting composite such as ICP content, electrical conductivity, surface morphology, and electromagnetic interference shielding effectiveness (EMI SE). The specific volume resistivity of the composite was as low as 0.3 Ω-cm, giving rise to about 36 dB of EMI SE over the wide range of frequency up to 1.5 GHz. We also prepared the elastic textile composites, exhibiting a monotonic increase of the electrical resistance with the elongation up to 50%. We, therefore, propose the elastic textile composite can be used as a strain sensor for large deformation.

Mechanical properties of wool fiber in the stretch breaking process

Short wool fibers obtained by the stretch breaking process can be blended with cotton fibers and processed in a cotton spinning system, which has a high production rate. For the structural property of the wool fiber after stretch breaking, the diameter and length of the wool fiber were measured as a function of time. The diameter of the broken fibers was finer than the diameter of untreated fibers. The fiber diameter at the break point was the finest and was more irregular than the original fiber. The broken fiber showed mechanical properties of increased modulus, decreased breaking strain, and increased breaking strength.

Preparation, chemical, and thermal characterization of nylon 4/6 copolymers by anionic ring opening polymerization of 2-Pyrrolidone and ε -Caprolactam

Nylon 4/6 copolymers based on 2-pyrrolidone (C4) and ε-caprolactam (C6) were synthesized and characterized as part of ongoing efforts to develop thermally stable, melt-processable 2-pyrrolidone (C4) based Nylons. Copolymers of various compositions were synthesized at between 50 and 100 °C via the anionic ring opening polymerization of C4 and C6 using a potassium tert-butoxide catalyst and a benzoyl chloride initiator. The polymers were characterized by NMR spectroscopy, DSC, TGA, GPC, intrinsic viscosity measurements, and X-ray scattering (SAXS and WAXS). Their chemical compositions and sequence distributions were obtained by 1H- and 13C-NMR spectroscopies, respectively. X-ray scattering was used to investigate the lamellar morphologies and the crystal structures of solvent cast films of the copolymers. WAXS revealed the presence of α-phase crystals in the copolymers. TGA data coupled with molecular weight and sequence distribution information indicated that the polymers’ thermal stability depended on both their chemical composition and their sequence distribution.

Synthesis of poly(2,6-dimethyl-1,4-phenylene ether) with controlled molecular weight via suspension polymerization catalyzed by amine–copper (I) complexes under various reaction conditions

The oxidative suspension polymerization of 2,6-dimethyl phenol (DMP) to poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was performed with the use of emulsifier in water–chloroform biphasic medium. The effects of DMP/catalyst mole ratio, ligands, emulsifiers, and 2,4,6-trimethyl phenol on polymerization were investigated in terms of molecular weight and yield. Various ligands were employed in the polymerization to investigate ligand efficiency. Intrinsic viscosity measurement data showed that the most efficient ligand was 1-methyl imidazole (Meim) in terms of molecular weight. By incorporating different amount of DMP in the monomer feed, it was possible to control the molecular weight of PPE in the oxidative suspension polymerization.

Evaluation of the structural properties of plain fabrics woven from various fibers using Peirce’s model

Peirce’s fabric model has been widely used to predict the structural behavior of various plain woven fabrics. The structure of plain woven fabric can be defined in terms of the warp yarn number, weft yarn number, warp fabric density, weft fabric density, warp crimp, and weft crimp. The warp and weft yarn diameters are calculated from the warp and weft yarn numbers, and the effective coefficient of the yarn diameter is defined by using this model. We have investigated structural properties, such as the effective coefficient of the yarn diameter, yarn crimp, and fabric thickness for two different fabrics in which the constituent yarns are assumed to be either incompressible or compressible. This model is also applied to various plain fabrics woven from cotton, rayon, wool, linen, nylon, acetate, polyester, and silk yarns.

New composite yarn with staple fiber and filament controlling the delivery speed ratio

In this study, we describe a technique to produce a new composite yarn with different cross-sectional and longitudinal appearances on a modified ring spinning machine. These new composite yarns are produced by adjusting the delivery speed ratio between staple fiber and filament. In order to examine the effect of the delivery speed on the yarn structure, we investigated the convergence points in the yarn formation zone, with various delivery speeds, using a high speed camera. The convergence point migrated from side to side depending on the delivery speed and, as a result, the produced yarn had various structures. We also evaluated the properties of composite yarns depending on the delivery speed ratios of the filament and staple fiber as well as the twist multiplier in the new composite spinning system. The delivery speed ratio changed the yarn properties, such as unevenness, imperfections, tenacity, elongation, and hairiness. The twist multiplier had a minor effect on the yarn properties for the same delivery speed ratio.

A study on the structural properties of plain fabrics using the lenticular model

The structural properties of a plain fabric were considered using the lenticular model. The structure of a plain woven fabric can be defined in terms of warp yarn number, weft yarn number, warp fabric density, weft fabric density, warp crimp, and weft crimp. Many structural variables of the plain fabric could be calculated by the lenticular model using these terms. Also, this model can be used to explain the geometry of the flattened yarns that occur during the weaving process. Flattening factors of threads for various types of fibers were calculated, compared, and explained with the number of yarn twist. Flattening factors were found to affect the structural variables of the fabric such as fabric thickness, air permeability, and yarn crimp. Yarn crimp was also studied with variation of the structural variables of the fabric.

Orientation Density Function of Ply yarn

Assuming that the individual fibers in a ply yarn have the form of a doubly wound helix, we simulate the paths of the individual fibers in the yarn. We show the fiber paths as a function of the fiber position in the single yarn, the number of twists of the single yarn and the ply yarn, and the direction of twist for the single yarn and the ply yarn. We also calculate the orientation angle, the orientation density function, and the mean of orientation angle in a ply yarn in order to predict the mechanical properties of ply yarn.Assuming that the individual fibers in a ply yarn have the form of a doubly wound helix, we simulate the paths of the individual fibers in the yarn. We show the fiber paths as a function of the fiber position in the single yarn, the number of twists of the single yarn and the ply yarn, and the direction of twist for the single yarn and the ply yarn. We also calculate the orientation angle, the orientation density function, and the mean of orientation angle in a ply yarn in order to predict the mechanical properties of ply yarn.

New definition of the fibrogram and its application to cotton blending

The fibrogram theory is newly derived from the superposition principle of the conventional staple diagram, in which the left-hand ends of the fibers have to share a common starting point in order for the fiber length distribution to be measured, and the right-hand ends of the fibers form points. It is shown that the fibrogram is the staple diagram of the fiber sample having different random starting points, as well as the double cumulative distribution function of the frequency length function in the length biased sample. Also, the various means, viz. the numerical mean length, numerical mean length in median, length biased mean length, and length biased mean length in median, and the various upper half means, viz. the numerical upper half mean length, numerical upper half mean length in median, length biased upper half mean length, and length biased upper half mean length in median, are discussed in relation to the cotton blending process.