Robert Harold Dettre

Dynamic contact angles and contact angle hysteresis

Abstract Contact angles have been measured as a function of the three-phase-boundary velocity. Large velocity effects observed with other techniques were not seen using the plate method. It is possible to relate the dependence of contact angles on velocity to surface heterogeneity.

Surface properties of polymers: I. The surface tensions of some molten polyethylenes

Abstract A modified Wilhelmy plate technique has been developed for the measurement of surface tensions of viscous polymers. The method requires no knowledge of liquid density and provides a means of assuring a zero contact angle for the polymer on the plate. The surface tensions of several silicone polymers with viscosities as high 106 centipoises have been measured. The method has also been used to determine the surface tensions of several molten polyethylenes as a function of temperature over the range 115° to 215°C.

The temperature dependence of wettability: Hexadecane on a fluoropolymer

Abstract It is often assumed that raising the temperature of a system increases its wettability. The contact angles of hexadecane on a fluoropolymer were measured over a 130°C. temperature range. The advancing angle was found to be independent of temperature and the receding angles increased slightly with temperature. It is postulated that large temperature effects indicate specific interactions such as adsorption or desorption.

Application of esca and contact angle measurements to studies of surface activity in a fluoropolymer mixture

Abstract ESCA and contact angle measurements have been combined in a detailed study of the effect of surface-to-volume ratio or thickness on the surface composition of coatings of a mixture of two fluoroalkyl methacrylate polymers which differ in the length of their fluoroalkyl side chains. These measurements show that the polymer component with the longer side chain is surface active in the mixture. The surface concentration of this component was found to decrease with increasing surfaceto-volume ratio of the coating.

Sorption of Surfactants in Polyester Fibers1

Sorption of amphiphilic compounds in polyester fiber above 200°C increases hydrophilicity of the fiber and facilitates oily soil removal. Hydrophilicity of the treated fabric depends upon the structure of the amphiphile. Sorption of carboxylic or sulfonic acid salts is related to their compatibility with the fiber or a fiber-like model solvent and decreases with the increasing size of their alkali metal ion: Li+ > Na+ > K+. The parent carboxylic acids to not increase hydrophilicity of the fiber. Quaternary ammonium halides with a long hydrocarbon chain increase hydrophilicity, but primary, secondary, or tertiary amine hydrochlorides are ineffective. The efficacy of nonionic surfactants in increasing hydrophilicity depends upon their hydrophilic-lipophilic balance (HLB) values; surfactants with HLB values of 13 to 16 are most effective.