The structure of carbons derived from acrylic fibers was analyzed by examination of structural peculiarities, i.e., anisotropy and distortions in the crystal. Changes in the structure of these fibers during the carbonization process and their dependence on stabilization conditions were investigated. During the carbonization process, a fiber structure was developed through a process whereby carbons in unorganized regions were gradually incorporated into crystallites as the carbonization temperature was increased. A marked increase in the fractions of crystallites and a discontinuous increase in the density of unorganized regions were observed at temperature of about 800°C, where growth of carbon layers associated with nitrogen elimination took place. Regularity in carbon layer stacking normal to the layer plane markedly increased at 1100°C. The microvoids in carbonized fibers were not those present in the stabilized fibers. At early stages of the carbonization process, the microvoids quickly disappeared, and at 800°C, they were recreated during the development of the carbon structure. Stabilization of the acrylic fibers minimizes loss of mass during the carbonization process. However, crosslinks formed by the stabilization prevented growth of carbon crystallites. Hence, as the degree of stabilization increased, the stacking height and the fractions of the crystallites in the carbonized fibers decreased, while the density and the fractions of unorganized regions increased. When the density of the stabilized fibers exceeded about 1.4g•cm-3, the excess oxygen uptake was eliminated as decomposition gases formed during the carbonization process, and the fractions of the microvoids in the carbonized fibers was increased.
The following three experiments were carried out to determine the safety limit for negatively charged polyester working wear. (1) Through the estimation of muximum (absolute value) voltage causing no discharge by a single contact with a grounded needle electrode, the limiting charged voltage of -3.5kV was obtained as a mean value. The safety limit calculated by adding the doubled standard devition to the mean value was -2.0kV. (2) By measuring the residual voltage on charged fabric after the multiple contacts (scanning) with a grounded sharp electrode, the safety limit causing no discharge was determined to be -2.0kV. (3) From the relation between discharge-initiating voltage of a metallic plate facing a grounded sharp electrode and the distance between these two electrodes, the discharge-initiating voltage at zero-distance was estimated to be -2.0kV in negative static field and 1.4kV in positive field. Considering the above mentioned results, the authors conclude that the salty limit for negatively charged working wear is -2.0kV. This safety limit is effective to avoid static hazards caused by discharges between fabrics and a sharp tip of metallic materials.
Highly filler-containing paper was prepared with two kinds of silica of different size, and the effects of filler sizes and contents on the sheet properties, such as pore volume, pore size distribution and physical strength were investigated. The sheet prepared without Filler (filler-free sheet) mainly has pores of 2-5μm diameter by a mercury intrusion porosimeter measurement. Sheets containing silica kept the pore structure of the filler-free sheet indifferent to the filler type and its content up to 50% or more. Silica of 26.1μm diameter (PW-20) couldn't increased the pore volumes of sheets containing it more than 30% over that of the filler-free sheet, even at its content of 75%. On the contrary, sheets containing silica of 9μm diameter (SD-8) marked an increase of pore volume up to four times over that of the filler-free sheet at the silica content of 85%. The mechanical strenght of the loaded paper fell down remarkably with filler contents, especialy in the case of the SD-8 sheets. These behavior of the pore volume increase and the paper strength reduction was explained by the difference of filler particle sizes.
To confirm the contribution of high molecular lignosulfonate to a powerful cellulose production system with Acetobacter xylinum, the commercial sulfite pulping waste fraction (CP powder) which led to high cellulose productivity was divided into a high and a low molecular lignosulfonate fractions which contained different quantities of carbohydrate by the sequential ethanol precipitation method. The culture media with the high molecular lignosulfonate fraction showed better cellulose membrane yields than those with the low molecular carbohydrate rich fraction or the whole CP powder. The more the high molecular lignosulfonate fracttion was purified, the more the efficiency for cellulose production increased. This means that the purification to eliminate both carbohydrates and low molecular fraction is effective. The prominent cellulose productivity was also observed by the addition of either sodium or calcium lignosulfonates on the market, which indicates that the high molecular lignosulfonate in CP powder is the dominant contributor for the high cellulose productivity. In order to clarify the contribution of the dispersing nature of the lignosulfonate, the effects of synthetic dispersant and natural digitonin were also investigated but they showed only a little effect.
Sorption and reaction of nitrogen dioxide on nylon substrate were investigated for the study of yellowing of fabrics on storage under the atmosphere. Yellowed nylon fabrics after exposure to NO2 gas were found to have two distinguishable visible absorption maxima at 390 and 440nm. These two absorptions changed in magnitude independently with the period of exposure to NO2 gas. XPS spectra of the yellowed nylon suggested that NO groups were introduced on the substrate by the exposure to NO2 gas. FTIR spectra also indicated that nitrosoamine was formed on nylon substrate. Sorption of NO2 on dry and wet nylon samples was measured by the Saltzman method. The sorption of NO2 on wet nylon and resulting yellowing of the substrate were more remarkable than those for dry nylon.
The mean activity coefficients (γ±) of sodium 4-(p-dialkylaminophenylazo) naphthalene-1-sulfonates [MN dyes, alkyl=methyl (MN), ethyl (EN), and n-butyl (BN)] in water were determined by means of vapor pressure osmometry (VPO). The γ± values for the dyes were much smaller than unity and decreased with increases in the concentration of dye and in the alkyl chain length of the molecule (MN > EN > BN). The γ± values for MN dyes over a wide range of the concentration were smaller than those for the methyl orange series with corresponding alkyl substituents. These results suggested that the γ± values for MN dyes were also affected by the naphthalene nucleus. The aggregation numbers (n) for the dyes were predicated by the relation between the mean activities and concentrations, and furthermore by the analysis of visible absorption spectra. At 50°C, MN dye existed in aqueous solutions as nearly a trimer (n=3) and EN dye as a tetramer (n=4), while BN dye formed much larger aggregates than the others. The formation of large BN aggregates was confirmed by the solubilization of a hydrophobic cationic dye (methylene blue)-BN complex into a concentrated BN aqueous solution.
The interaction of acid azo dyes having alkyl chain groups of different length with α-, β- and γ-cy-clodextrines (CD) in aqueous solution was investigated by means of the visible absorption spectra at different temperatures. The presence of CD (1×10-6-10-2mol/L) in the dye solution (5×10-5mol/L) changed the absorption spectra, and the degree of the change was in an order of the increasing alkly length in the dyes. With an increase in the concentration of CD, the absorption spectra changed keeping an isosbestic point. The stoichiometry of the binding was confirmed as equimolar by a continuous variation method. Upon assuming the molar ratio of the complex as 1:1, the binding constants were calculated by a nonlinear least-squares method. The mode of the interaction was estimated as an inclusion type. The presence of the alkyl chains in the dye molecule increased the binding constant. The fitness of the dye to the cavity of CD was suggested to affect the binding constant. Based on the temperature dependence of the binding constants at different temperatures. the compensation relation between entropy and enthalpy changes of binding was found and the contribution of entropy to the process was discussed.
Weatherability of membrane materials for membrane structures is usually evaluated by carrying out outdoor exposure and accelerated exposure tests on them. The tensile test and Scanning Electron Microscopy (SEM) observation were conducted on exposure-tested specimens of PVC-coated polyester fabric (PVC membrane) and PTFE-coated glass fiber fabric (PTFE membrane). The specimens were taken from the fabrics, some having been subjected to outdoor exposure test and the others subjected to accelerated exposure test. It was aimed at determining weatherability of the exposure-tested fabrics and finding, if any, correlation between the two exposure tests. Retained tensile strength after 5-years-outdoor- and 5000-hours-accelerated-exposure tested PVC membrane decreased to 75% and 72%, respectively, from their initial value, while that of 10-years-outdoor-and 10000-hours-accelerated-exposure-tested PTFE membrane slightly changed to 80%, 81%, respectively. Micro cracks were observed by SEM on the PVC membrane surface exposure-tested by both methods. Any morphological change could not be found on the PTFE membrane exposed with 10000-hours-accelerated-tests. It was determined that 10-years of outdoor exposure test period roughly corresponded to 8000-hours (in PVC membrane) and 11000-hours (in PTFE membrane) of accelerated exposure tests with respect to decrease in tensile strength value alone.