The moisture sorption properties of poly (ethylene terephthalate) (PET) fibers including a series of high-speed spun filaments and a series of chemically and/or physically modified staple fibers were investigated in terms of the moisture sorption isotherms and of the heat of moisture sorption. The isotherms for the unmodified PET fibers were found to be composed of the solution component following the Henry's solution law and of an additional swing-up component at vapor pressures higher than ca. 25mm Hg at 30°C. The isotherms for the chemically modified hygroscopic fibers were composed not only of the solution component, but also of an adsorption component following the B. E. T.'s or Langmuir's equation and further of some condensation component. The Henry's law solubility coefficient K_D was linearly dependent on the X-ray noncrystallinity (1-X_x) for most of the PET fibers. In general, the higher the degree of crystallinity, the lower was the value of K_D; e. g., a filament spun at a particular rate around 7000m/min yielded a minimum value of the coefficient and a maximum value of the crystallinity among the series of high-speed filaments. The temperature dependence of K_D agreed well with the van't Hoff relation, leading to an enthalpy difference of ΔH_D_??_-9.6kcal/mole between the solution water and the water in vapor. The thermogram for wetting of dried specimen revealed at least qualitatively the simultaneous occurrence of a rapid endothermic process and a slow exothermic process. These results showed the existence of three components of sorbed water in PETs; the solution component in a little less interacting state, the adsorption component in much more interacting state, and the condensation component in a little more interacting state than in the liquid state of water.

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The high-strength poly (vinyl alcohol) fibers were prepared by the crosslinking/wet spinning method (B-type fibers). The mechanical and thermal properties of the fibers were compared with those of conventional fibers prepared by non-crosslinking type method (N-type fibers). The mechanical properties of the B-type fibers were much superior to those of the N-type fibers. The drawability of pre-heat-treated B-type fibers was higher than that of N-type fibers. The high drawability of B-type fibers was explained by “topological memory effect” due to removable crosslinks.

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The formation of the characteristic surface of cupraammonium rayon fibers was investigated using the electron microscope. The rough surface of cupraammonium rayon, similar to that of pine trees, was often considered a result of the coagulation that takes place under flowing at large deformation rate in the coagulation zone of the spinning process. In this experiment, never-dried gel fibers were obtained at a stage just before the drying process of the production line. Water in the gel fibers was first removed by a centrifuge, and then the fibers were dried under various drying conditions. Freeze and critical-point drying methods were employed for sample preparation to reduce distortions of the structure of the dried fibers. Electron microscopic observation proved that the surface layer of the gel fibers consists of microfibrilar networks. The water content leveled off at about 400% when fibers being dried with the use of the centrifuge. The surface topology of the fibers up to 100% moisture content approximately preserved the fibrilar structure such as the never-dried gel fibers. Upon further drying, fibril to fibril contact caused the fibrilar networks collapse and a new surface developed. The surface structure of cupraammonium rayon fiber, therefore, largely depends upon the drying process. Air drying at room temperature formed a relatively smooth surface. The rough and granulated surface appeared with the rapid drying in an air oven at high temperatures. Shrinkages and/or wrinklings of the fibrils introduced during the drying process played an important role in forming the characteristic surface structure. The experimental results show that the drying process rather than the coagulation process, governs the formation of the surface structure of the cupraammonium rayon fibers.

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Dielectric constant ε′ and dielectric loss ε″ at microwave frequencies were determined for hand-sheets of various densities prepared by changing freeness, mesh size for fractionation and pressure for wet pressing. Both ε′ and ε″ at 4.0 GHz increased linearly with increasing density. Empirical formulae ε′=0.531+3.07 ρ and ε″=-0.098+0.619 ρ for handsheets of hardwood pulps were obtained for densities between 0.5 and 1.0g/cm³. The correlation coefficient between ε′ and ρ and between ε″ and ρ were 0.994 and 0.984, respectively. These formulae were interpreted on the basis of proportionality of density to the number of dipoles per unit volume in the paper sheet.

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Based on the surface characterization (FT-IR) of acrylic acid grafted polyester fabric (PET) after treated with aqueous Na₂CO₃, both the variation of wettability of PET to water and the improvement of soil release properties were highly correlated to the amount of introduced COON groups on fiber surface (SGD). The capillary spreading measurements were employed to compare the wettability of fabrics and surface treatments. The values of A₁, the area at the time 1min, and n, the slope of spreading of water during phase II, of grafted PET increased and decreased with increasing in the grafting degree or SGD, respectively. It was explained in terms of surface modification to more hydrophilic and a smaller advancing contact angle of the fiber to water (θ).

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Our previous study showed that an anion exchangeable cotton yarn was capable of adsorbing hydrolyzed reactive dyes in waste water, This yarn was prepared by Hofmann-degradative treatment of poly (acrylamide) -cotton graft copolymers by using hypochlorite. In this paper we report on the improvement of the preparation of anion-exchangeable cotton yarns. For enhancing grafting ratio and conversion ratio of the graft copolymerization of acrylamide onto cotton yarns, a Fe⁺²-H₂O₂ redox system was used as an initiator. The ferrous salt was adsorbed on cotton yarns and then added to a monomer solution containing H₂O₂. This redox system as an initiator gave three times higher grafting ratio than the cerium salt system. The conversion ratio of graft copolymerization was dependent on the monomer concentration and the bath ratio. The maximum conversion ratio (78%) was obtained with 10% acrylamide at bath ratio, 1:8 by using this redox system. The capacity of yarns for adsorbing hydrolyzed reactive dyes was dependent on the conditions of Hofmann-degradative treatment. The maximum capacity of dye adsorption (230mg/g) was attained when the grafted yarn was treated at room temperature for 6h in the solution containing a large excess of NaOH and hypochlorite, where the active chlorite was 1.4 times as much as the molar quantities of the grafted acrylamide. The adsorbed dye on the cotton yarn was easily eluted with dilute NaOH solution and the maximum desorption of dyes (96.3%) was attained with 0.05% NaOH solution. This yarn adsorbed the dye more effectively even at a high flow rate (SV 215) than the activated carbon in the column method.

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