The purpose of this paper is to predict the load-elongation relationship of parallel filament yarn not only at the yield point and at the breaking point but also in the state of whole stress-strain process. A theory and a simulation of tensile properties of the yarn were proposed by using a method of statistics and the Monte Carlo method, respectively, both based on the parameters of idealized stress-strain curve of filament fibers. A comparision between the results of theoretical calculation, simulation and experiments showed good agreement. In addition, for tensile properties of the yarn, the influence of the coefficient of variance of yield strain and stress of the fibers was studied in terms of the theory and simulation.

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PET films stretched under different conditions were treated by radio frequency low-temperature plasma with various gases, and the surface topographical change was investigated by wettability and the introduction of functional groups. The results indicated that undrawn and biaxially drawn films treated with plasma were etched irregularly and randomly, but regular etching structure (seashore structure) which was made at right angle to the stretching direction was observed on uniaxially drawn films treated with plasma. This tendency was especially conspicuous, in oxygen and argon gas plasma treatment, but the degree of etching of the surface treated with nitrogen-containing gas plasma such as nitrogen and ammonia was small because nitrogen atoms were incorporated into PET surface during plasma treatment, Untreated PET films exhibited different wettability according to stretching conditions, but once they underwent the low-temperature plasma treatment, they showed nearly equal wettability irrespective of stretching conditions. The results showed that the oxygen gas plasma improved surface wettability exceedingly among the gasses used in this study, and it gave the greatest critical surface tension. Hydrophilic functional groups may have been introduced into PET surface treated with oxygen gas plasma, judging from the ratio of dispersion force and polar force calculated from expanded Fowkes equation.

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A variety of poly(ethylene terephthalate) (PET) fibers having different fine structures were treated with RF discharge low-temperature plasma, and effects on etching were investigated by SEM. In particular, etching profile appeared conspicuously by oxygen plasma on the PET fiber surface was affected by fiber orientation and crystallinity rather than intrinsic viscosity. The investigtion revealed that the PET fiber of low orientation and low crystallinity is randomly etched, that is to say, irrespective of fiber axial direction, whereas the PET fiber of high orientation and high crystallinity is etched at right angles to the fiber axial direction. The regularity intervals are related to the long period of fine structure, suggesting that noncrystalline portion is selectively etched. It has been proved that etching profile of PET undrawn fiber treated by low temperature plasma was changed after streched and this surface topographical structure was very different from that of plasma-treated PET fiber which had been drawn before plasma treatment.

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Photoresponsive cellulose p-phenylazobenzoates (AB-celluloses) with degrees of substitution (DS) of 2.2-2.9 were prepared by repeated reactions of cellulose powders with p-phenylazobenzoyl chloride. The AB-celluloses were found to be soluble in some organic solvents and form lyotropic liquid crystalline phase at the concentrations higher than a certain critical concentration. The critical concentration in tetrahydrofuran was higher than that in less polar chloroform, and it decreased with increasing DS of the AB-cellulose. The critical concentration was found to increase 3 to 5 wt% with UV light irradiation. The ordered structure once formed at the concentrations slightly higher than the critical concentration disappeared with UV light irradiation, and then on standing after interruption of the irradiation it restored again, although not perfectly. The change in the critical concentration with UV light irradiation and disappearance of the ordered structure thereby were explained by the isomerization of azobenzene moiety in the AB-cellulose from trans to more polar cis from. When the AB-cellulose was irradiated with UV light for a short time, the ordered structure continued to decrease even after the interruption of irradiation. The time required for perfect disappearance of the ordered structure after interruption of the UV light irradiation decreased with increasing irradiation time and reached zero at a certain time depending on the concentration of the AB-cellulose; the time required for the disappearance increased with increasing concentration of the AB-cellulose.

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The effects of humidity and oxygen on the photofading of Crystal Violet (CV) in nylon 6 film were studied in detail. Both moisture and oxygen were necessasy for the formation of Michler's Ketone. The effects of temperature and humidity on the photofading of CV in nylon 6 and polyester films were discussed in terms of kinetics. The fading rate was accelerated with rises in temperature and humidity for both films, and the rate was lower in polyester film than in nylon. The quantum yield in film decreased with the progress of decay, whereas it was almost unchanged in solution. The relationship between relative quantum yield (φ) in film and absorbance (A) at λ_max was expressed by the equation, φ=β(A-a₀)^m. The parameter m indicates the ease of decrease of the rate with the progress of decay. The influences of temperature and humidity on the value of m were compared. The value of m depends on the initial absorbance in some cases. At elevated temperatures m has smaller value in almost all the cases.

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The subject of the title was investigated. The higher crystalline fibers hot-drawn at temperature above 400°C had poor long-term thermal stability (290°C), regardless of imidization methods of the precursor fibers, presumably as a result of the physical deterioration which was accompanied by increase in crystallinity caused by the heat treatment. The lower crystalline fibers which were chemically imidized and drawn 1.1-1.2 times at 290°C had moderate tensile properties and excellent heat durability; i.e., percents of both tenacity and elongation retained after 65h at 290°C in air were about 100%.

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