No abstract

The contact angles of water and organic liquids have been measured on films of corn starch, amylose, amylopectin, viscose-type cellulose and polyvinyl alcohol. Hydroxyl-containing liquids tend to form unstable angles with complications due to sorption and swelling effects; however, the initial advancing contact angles of water on starch and cellulose films are finite, ranging from 83 to 15°d epending upon the degree of prior equilibration; only on starch is a stable finite water contact angle (40°) found. Raw cotton fibers are very hydrophobic and the impurities responsible are progressively removed by solvents and alkali. A number of organic liquids, mainly of halogenated type, form stable, finite and reproducible angles on these polymer surfaces. As has been found by Zisman, linear relationships hold between the cosines of the contact angles and the surface tensions of the respective liquids. Each of the polymers possesses a characteristic line and the several lines extrapolate to critical surface tensions (y") between 35 and 42 dynes/cm. The relative positions of these lines suggest that the wettabilities, and free surface energies, of the polymers increase in the order starch, amylopectin, amylose, polyvinyl alcohol, cellulose. In contrast to some other types of polymers, small, or negligible, hysteresis effects were found. Foils were prepared by casting from solutions onto various substrates and stripping off. The wetting characteristics of the air-sides and the substrate-sides of these foils were significantly (up to 30°) different with the effects being most pronounced for amylose and least for polyvinyl alcohol. Induced orientation is postulated and the polar-inducing order of substrates is glass, mercury, Lucite, Mylar, polystyrene, "air," Kel-F and Teflon. (20) E.

Special Issue: Special Issue to Honour Professor Dr. Rudi van Eldik on the occasion of his 70th birthda

No abstract

In this study, we examined the influence of surfactants on the adsorption of polymers on cotton fibers. The extent of polymer adsorption on cotton was determined directly by means of fluorescence spectroscopy using fluorescently labeled polymers. The investigation of polymer adsorption in the presence of different types of surfactants and for a large range of differently structured polymers allows us to obtain a rather general picture of this important issue. Systematic relationships between the presence of surfactant and the type of polymer can be deduced but cannot be cast in simple terms such as electrostatic interaction but instead depend on the detailed interaction between the surfactant and polymer both in solution and adsorbed on the cotton surface. A particularly complex situation arises for the case of oppositely charged surfactant and polymer because of the possibility of precipitate formation. The study of such complex systems not only is of scientific interest but also is of great commercial interest because both polymers and surfactants are parts of detergent formulations and cotton is one of the most abundantly used materials for fabrics.