No abstract

Cotton fabrics were oxidized with nitrogen dioxide and sodium periodate and crosslinked with dimethylol urea (DMU) and with dimethylol dihydroxy ethylene urea (DMDHEU) by the pad-dry-cure process. The effect of pre- and post-oxidation to resin treatment on the crease-resistance and tensile properties of cotton fabrics have been investigated. The results show that crease-recovery angle increases with degree of oxidation, and further periodate oxidation causes the release of strain in cellulose structure, thereby lowering the loss in tensile strength. Resin treatment, on the other hand, improves alkali sensitivity of periodate oxycellulose. Periodate oxidation and resin treatment therefore seem to complement each other.

The dissociation, capacity, swelling, and water content of crosslinked methacrylic acid—methyl methacrylate resins have been measured. Resins were prepared with different degrees of crosslinking for the same carboxylate content, and vice versa. The ionic strength of the external solution was also varied, and the behavior of commercial resins compared with that of the laboratory resins. Potentiometric titration curves were obtained, and curves were also obtained by back‐titration of the salt form of the resins with acid. The capacities showed that almost all carboxyl groups are accessible in resins containing 2.5% or 4.0% divinylbenzene, but not in those containing 8% or 12%. For these highly crosslinked resins the back‐titration curves differed from the forward curves. Apparent dissociation constants pK′a = pH + n log [(1 − α)/α] decreased with increased ionic strength, increased with increased crosslinking, and showed no trend with carboxylate content. Swelling is decreased by increased salt concentration, particularly for lightly crosslinked resins. Maximum swelling is achieved at about 80% dissociation. The reciprocal of the swollen volume is proportional to the per cent of divinylbenzene. Commercial resins showed much lower swelling than laboratory prepared resins ostensibly having the same composition. The Gibbs‐Donnan theory of resin dissociation was applied to calculate the intrinsic dissociation constant (pK′0). Assuming a model of randomly kinked chains dissolved in the sorbed solution, good agreement with the expected value of 4.85 was found (calcd. pK′0 = 4.81 = 0.14), except for the most highly crosslinked resins. For polyampholyte resins, agreement was found by using a model having a uniform potential distribution throughout the resin (pK′0 = 4.9).

Ion exchange and sorption of charged molecules such as dyes, crosslinking agents, etc., by cotton cellulose very much depend on the charge on cellulose, which in turn is known to depend on the external pH of the medium. In order to understand the role of various fixed groups in cellulose in its polyelectrolyte behavior, the standard cellulose was deliberately oxidized with nitrogen dioxide and sodium periodate, and the sorption of formaldehyde and dimethylol dihydroxyethylene urea by these oxycelluloses as well as by alkali‐treated nitrogen dioxide–oxycellulose was investigated. The results obtained are interpreted in terms of polyampholyte behavior of oxycellulose. The nitrogen dioxide–oxycellulose is positively charged and is a polycation in acidic medium due to protonation of aldehyde groups while it is negatively charged and acts as a polyanion in slightly acidic to alkaline medium due to dissociation of carboxyl groups.

A etudy haa been made of the kinetica of the removal of water from native, alkaliswollen, and regenerated duloeic fibem under well dehed conditions of experiment. In all caw, the rate of evaporation m e appeam to be made up of five dietinct and separate portions, and there are four points on each curve at which sudden changee of direction take place. From the changea in the rates of removal of water, attempta have been made to determine the amounts of water present in celluloeic fibem with different degreee of aeaociation with the fiber subetance and to compare them valuea with thoee recorded by other workem employing different techniques. Removal of primary adsorbed water from different celluloeic fibers could be beat reprseented by three Mitt phaeee, the firat two of which obey kinetics of reaction of firat order and with apparent activation energy of the order of 8-9 kd./mole. An attempt haa also been made to calculate the radii of crrpillariea preaent in water-awollen celluloeic fibers. Y43