Chang H Jho

Drop weight technique for the measurement of dynamic surface tension

Abstract We investigated the dynamic drop weight technique originally proposed by Brady and Brown [“Monomolecular Layers” (H. Sobotka, Ed.), p. 33. AAAS, 1954 ] for the determination of the dynamic surface tension. The principal empirical equation on which their method is based was found to be inconsistent with our extensive new data. It is concluded that their equation was a result of insufficient data. In the course of our investigation we discovered a new important empirical equation that enabled us to develop a simple, straightforward method to determine the dynamic surface tension of both aqueous and nonaqueous surfactant solutions.

The effect of viscosity on the drop weight technique for the measurement of dynamic surface tension

Abstract The effect of viscosity on the drop weight technique for the measurement of dynamic surface tension has been investigated. The previously discovered empirical equation (master equation) was found to depend generally on the viscosity. This equation is the basis for the correction of the hydrodynamic effect necessary for the determination of the dynamic surface tension. It was confirmed, however, that the master equation is valid independently of the viscosity within the viscosity range of liquids (⩽15 cP) used to construct the equation. It was also shown that the equation is independent of the physical properties of the liquids and the tip radius, provided the dimensionless surface tension number, N γ = pRγ η 2 > 10 2 , where γ is the surface tension, R is the tip radius, and p and η are the density and the viscosity, respectively.

Spreading of aqueous solutions of a mixture of fluoro- and hydrocarbon surfactants on liquid hydrocarbon substrates☆

Abstract We have studied the spreading kinetics of aqueous solutions of a mixture of hydrocarbon and fluorocarbon surfactants on liquid hydrocarbon substrates. A commercial AFFF (aqueous film-forming foam) agent was used as the mixture of the surfactants. An empirical relation was established between the rate of spreading and experimental parameters involved in the spreading, such as the equilibrium and dynamic surface and interfacial tensions, the spreading coefficient, and the concentration of the spreading solution.

Industrial Applications of Surfactants, and Surfactants in Emerging Technologies

Surface sizing generally refers to the process of imparting paper resistance to wetting by liquid through the surface modification of paper. In this study, the interfacial phenomena in surface sizing were examined by considering the penetration of liquid into the porous structure of paper. By modifying Fowkes’ original study on the work of adhesion [F.M. Fowkes, Ind. Eng. Chem..56, no.12,40 (1964)] and Washburn-Lucas model [E.W. Washburn, Phys. Rev., 17,273 (1921); R. Lucas, Kolloid-Z, 21,15 (1918)] on capillary penetration, a theoretical framework on the penetration of liquid into surface-sized substrate is presented. Theoretical analysis was made to determine the criteria and governing factors in developing the resistance to polar and nonpolar liquids. The authors gratefully acknowledge the support of the management of PPG Industries for this work.

Effect of mold material on the surface properties of an acrylic copolymer

Abstract We have demonstrated that the surface properties of a copolymer of glycidyl methacrylate and acrylic monomers depend on the material of the mold in which the polymerization reaction was carried out. On the basis of surface free energy measurements by contact angle goniometry, it is shown that the polarity (polar component of the surface free energy) of the polymer surface is directly related to the polarity of the mold surface; the more polar the mold material is, the more polar or hydrophilic the polymer surface becomes. The study of the effect of the mold material was also extended to the polymer samples that were further chemically treated with tris(hydroxymethyl)aminomethane. Upon treatment the polymer showed an increased polarity due to the creation of surface hydroxyl groups, but did not follow the same direct relationship between the polarity of the mold and that of the polymer, as observed with untreated polymer; instead, a surface saturation effect was observed. These observations are explained on the basis of the preferential adsorption of epoxy groups at the polymer surface induced by the polar mold surface during the polymerization reaction.