The water sorbed in a series of poly( para -phenylene terephthalamide) (PPTA) fibers (regular Kevlar, Kevlar 49, Kevlar 149, and a heat treated PPTA fiber) was characterized by analyzing the moisture sorption isotherm and thermodynamic quantities derived from calorimetric measurements of heat of moisture sorption. The maximum volume of adsorbed water in Langmuir's monolayer fashion per unit mass of dry material v m normalized by the degree of noncrystallinity was much larger for the series of PPTA fibers than that for nylon fibers, such as 6, 66, and 46, possessing almost the same concentration of peptide groups as the PPTA fibers. The number of water molecules adsorbed in monolayer fashion per each peptide site in the noncrystalline region was around 0.4 moles/mole for the PPTA fibers and about 2.2 times larger than that for the nylon fibers, all at 30°C. The hydration enthalpy ΔH L at dryness and the hydration entropy TΔS L near dryness were -25 ∼-35 and -10 ∼ -12 kJ /mol, respectively, both at 30°C, when liquid water was taken as the reference. These values are about 1.5 times larger than those of nylon 6 fibers, large enough to assign the initially sorbed water in the PPTA fibers as doubly hydrogen bonded and in a highly ordered state like the crystal lattice of ice. These results indicate that the bulky and rigid phenyl ring in the aromatic polyamide chain opens the space for each peptide site to adsorb moisture more efficiently than the site in the aliphatic polyamide chain.Poly (para-phenylene terephthalamide ) ( PPTA ) is a liquid crystalline polymer developed by E.I. du Pont de Nemours & Company in 1971 to produce a series of aromatic polyamide fibers using a wet spinning process from an anisotropic solution in sulfuric acid [ 1 ] . The fibers, commercially named Kevlarf), exhibit high tensile strength and elastic modulus in bulk [ 7 ] . The tensile modulus in bulk has reaches as high as 125 GPa for Kevlar 49 and 180 GPa for Kevlar 149 [ 8 ] , values that are fairly close to the crystal lattice modulus in the c-axis direction observed by x-ray diffraction as 156 GPa [ 28 ] and to that calculated theoretically from chain conformation as 182 GPa [ 35 ] . The fact that the tensile modulus in bulk is fairly close to the lattice modulus must be interpreted in terms of a high degree of crystal orientation toward the fiber axis as well as a high degree of crystallization, possibly in extended chain fashion, both arising from flow-induced orientation and crystallization of PPTA during the wet spinning process of the liquid crystalline solution.PPTA fibers such as Kevlar 29 and 49 have hygroscopicity as high as nylon 6 and 66 fibers, attaining moisture regains of around 4% (g/g) and 7% (g/g) at 65 and 100% relative humidities, respectively, at 30°C [23]. These moisture sorption behaviors are consistent with the fact that PPTA fibers have almost the same molar concentration of peptide linkages ( which must act as moisture adsorption sites) as nylon 6 and 66, but are inconsistent with t...

ABSTRACT:The interaction of moisture with nylon 6 was investigated using an FT-IR spectroscopy over a near-infrared range of wavenumbers from 4500 to 8000 em -1 to cover the first overtones of (2vCH) and (2vNH) as well as the water sensitive 5100 and 6900 em -1 bands, a combination of (<10 H)+(v.,0 H) and a combination of (v,0 H)+(v"'0 H), respectively. Two types of differential procedures were performed to separate the contribution of the water sensitive bands from the entire spectrum: i.e., subtracting the spectrum of the test specimen conditioned at dryness of 0% relative humidity from that conditioned at a given relative humidity of x% (procedure A) or the spectrum for x% from that for (x + tl.x)% (procedure B), both as functions of the given relative humidity of x%. From the areas of the water sensitive bands thus separated, the moisture sorption isotherm could be composed in fairly good agreement with that obtained by a gravimetric method. The 6900 em -1 band of bulk water as well as those in the differential spectra, were decomposed into three components of a Lorentzian function, sub-band I, 1-11, and II in the order of descending wavenumber. They were attributed to three kinds of water species differing in the degree of hydrogen-bonding covering singly to doubly hydrogen-bonded water (ice-like water) species. It was found that the water species, which more strongly interact with each other, also more strongly interact with the water accessible sites of nylon 6 to form fewer number of layers of adsorption in the sense of B.E.T.'s multilayer adsorption or the core portion of water cluster in the sense of Hill's multimolecular adsorption. Semi-quantitative comparison was made between the characterization of the sorbed water by the B.E.T.'s multilayer adsorption and that by the present FT-IR spectroscopy.KEY From the temperature dependence of the moisture sorption isotherm, the thermody-

Aims: Scedosporium apiospermum sometimes causes serious infectious diseases on the skin of immunodeficient subjects. Antifungal effects of fatty acid salts in soap against S. apiospermum were investigated under different water conditions. Methods and Results: Ultrapure soft water (UPSW) was generated by the water softener with cation-exchange resin. The calcium and magnesium ions were replaced with sodium ions in UPSW. Scedosporium apiospermum was incubated with different fatty acid salts that constituted soap in distilled water (DW), tap water (TW) and UPSW. After incubation, the number of fungi was counted. Among the fatty acids, palmitic acid salt (C16) reduced the number of S. apiospermum. UPSW enhanced the antifungal effect of C16 on S. apiospermum. The absence of both calcium and magnesium ions and the existence of sodium chloride in UPSW were responsible for its antifungal effect. In addition, repeated short-term treatment with UPSW and C16 decreased the number of S. apiospermum. Conclusions: Antifungal effects of C16 on S. apiospermum were demonstrated. Moreover, the use of UPSW promoted the antifungal effect of C16. Significance and Impact of Study: This study provides the preventive method for diseases associated with S. apiospermum infection using novel palmitic acid soap in UPSW.

Twelve kinds of cellulosic

The interaction of water