Personal Products Co.

For maximum liquid-holding capacity, an uncompressed fibrous assembly requires wettable fibers of high wet modulus. Tests with rayons of various denier, state of finishing, and modulus indicate that, for compressed absorbents, it also is desirable to minimize the required compaction forces by reducing the dry modulus and resilience of the fibers. The use of wet crosslinked rayon, which has the requisite combination of wet and dry properties, leads to significant improve ments in absorbency. The effect of increasing bulk density on the liquid capacity per unit weight and capacity per unit volume of absorbents is discussed, and a mechanistic description of the latter is presented.

A method is described for measuring in absolute units the rate at which the surface of a continuous filament or yarn becomes wet when in contact with liquidWhen cotton and rayon yarns interact with H2O, the rate of surface wetting is dependent on the temperature of the water as well as the finish of the yarn.When plotted according to the Arrhenius equation, most data indicated 2 straight-line segments.Evidence supports the hypothesis that the double-segmented Arrhenius curves arise from melting of a constituent of the yarn or the finish.The energy of activation ranged from 1.6 to 9.1 kcal/mole for the lower-temperature segments and higher for the others.Measurements on boiled-off cotton yarn indicated that long Draves-test sinking times were highly dependent on the rate of surface wetting.The skein test is virtually insensitive to rates of surface wetting >0.5 cm/sec, which is very slow compared to practical production speeds.

, Phenomena related to the equilibrium take-up and retention of fluid in porous media can be explained and predicted in terms of the capillary sorption cycle (CSC) formed by the absorption and exsorption isotherms. An experimental method is described for determining the CSC as well as the simultaneous changes in the bulk volume of the porous medium as it cycles between 0 and 100% fill-up. The complex shape of the CSC and the, sometimes highly significant, differences between the first and all subse quent cycles can be explained in terms of the mechanism which causes volume changes. The method of analysis provides a tool for investigating the capillary sorption proper ties of heteroporous media, such as fiber masses of different composition, structure, and bulk density. This has been demonstrated by applying the criteria of sorption equi librium to phenomena related to the spontaneous fill-up and capillary transfer of fluid in the pore system of fiber masses.