The reducible time, temperature, and fiber length effects in bending creep under constant load for the epoxy and unsaturated polyester resins reinforced with planar randomly oriented short glass fibers have been studied. For both composites, regardless of the interfacial treatment, the creep of matrix could be reduced by the fiber filling. This effect was remarkable with the increase in the length of reinforcing fiber. The creep behavior was well reproduced by a formula that took account of the strain rate and the temperature dependence of critical fiber length. At a given fiber length, a master curve could be drawn for the logarithm of creep compliances plotted against logarithm of time at a certain temperature by shifting the curves obtained at different temperatures along the axis of time. The shift factor for the composition of the master curve could be expressed by the Arrhenius equation. The master curves for different fiber lengths could be further reduced into a composite curve by shifting them along the axis of time. The logarithm of the shift factor decreased linearly with an increase in the aspect ratio of reinforcing fiber.
The relation between the curing condition and the cross-linking structure has been studied for rayon, mercerized cotton and cotton fabrics finished with DMEU resin under various conditions of curing time, temperature and catalysts. From the results obtained, the reactions between DMEU resin and cellulose were discussed. The competitive reactions between condensation reaction of resin itself and cross-linking reaction of the resin with cellulose were elucidated from the quantities of Cell-OCH2-N and N-CH2OCH2-N during DMEU resin finishing. These reactions were affected by temperature, and the type and concentration of the catalysts. In general, higher temperature and higher acidity of catalyst were in favour of the cross-linking reaction between resin and cellulose, and tended to form the cross-links of shorter length. It was also found that the condensation reaction of resin itself was initiated with the formation of N-CH2OCH2-N and followed by the decomposition of N-CH2OCH2-N into N-CH2-N and free CH2O. The later stage of the reaction was influenced by the curing temperature and the catalyst. Different types of cellulose, such as rayon, cotton and mercerized cotton, showed a similar reaction mechanism, but the rate of reaction and the length of cross-links were varied. It was found that the reaction rate was the highest for rayon, modest for the mercerized cotton, and the lowest for cotton. On the contrary, in terms of the length of cross-links formed, cotton showed the greatest, and the mercerized cotton came next which was followed by rayon.
Maximum current and diffusion current in polarography were measured for the solutions of acid dyes and the dye-gelatin systems. The effect of the acid dye in suppressing the oxygen maximum current was influenced by the presence of gelatin. The diffusion current in the acid dye-elatin system decreased in comparison with that of the acid dye alone. However, the current increased when urea was added to the Acid Red 88-gelatin system, because urea broke the binding between the dye and gelatin. In addition, visible spectra of the same solutions were measured and the dialysis experiments were carried out. The variations of the apparent molar extinction coefficient at λmax and the large differences in the absorbances of the solutions inside and outside the membrane after dialysis were observed. These results evidenced some interactions between the acid dyes and gelatin. The interactions were exothermic and were assumed to be not only ionic but also hydrophobic.
The relationship between hydrotropy and molecular weight of polyoxyethylene glycol (POEG) has been studied by measuring spectrophotometrically the solubilities of disperse dyes in the aqueous solution of POEG. Disperse dyes used were C. I. Disperse Red 1 and C. I. Disperse Violet 1. Solubility of the dyes increased with increasing concentration of POEG. The larger the molecular weight the increase in the solubility with increasing concentration of POEG was steeper, but became independent of the molecular weight as it went up over about 1000. On the other hand, a linear relation was found to hold between reduced viscosity of the aqueous solution of POEG and the molecular weight beyond 1000. These results elucidate that POEG with molecular weight above 1000 may form itself into a random coil and exhibit the behavior characteristic of a polymer in the aqueous solution, by which the favorable hydrotropy may be caused. It has been found that the solubilization of disperse dye in the aqueous solution of nonionic surfactant takes place in the polyoxyethylene region of the micelle, and the solubilization power is constant independent of polymerization degree of the poly-oxyethylene group4). The present results seem to suggest the polymer-like behavior of the nonionic surfactant micelle in the aqueous solution.