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SYNOPSISContact angle measurements with three different liquids were performed on: ( i ) butyl rubber PB 101-3 (Polysar Ltd.) and (ii) Dow Corning 236 dispersion. Contact angles were measured at different temperatures within the range from 23°C (room temperature) to 120°C. The surface tensions, ysV, of the polymeric coatings at each temperature were calculated from the contact angles. The temperature coefficients of the surface tensions, dysv/ dT, i.e., the surface entropies, were established for the temperature range covered. I NTRO DUCT10 NThe contact angle and surface tension properties of elastomers and coating materials are known to be important parameters in predicting adhesion. Many industrial processes either require strong adhesion or no adhesion at all. Adhesion to the inner walls of a reactor vessel during polymerization is just one example. Contact angles are readily measured on solid surfaces, and it is generally believed that contact angle measurements is the best approach to the determination of solid surface tensions.The contact angle of a liquid drop on a solid surface is defined by the mechanical equilibrium of the drop under the action of the three interfacial tensions: solid/vapor, ysv, solid/liquid, ysL, and liquid/ vapor, yLv. The equilibrium relation is known as Young's equation:where 8E is the equilibrium contact angle. This equation yields a single, unique contact angle. In practice, however, the contact angle made by an advancing liquid (8,) and that made by a receding liquid (8,) are not identical; almost all of the solid surfaces exhibit contact angle hysteresis (the difference between the advancing and receding contact
SYNOPSISContact angle measurements with three different liquids were performed on: ( i ) butyl rubber PB 101-3 (Polysar Ltd.) and (ii) Dow Corning 236 dispersion. Contact angles were measured at different temperatures within the range from 23°C (room temperature) to 120°C. The surface tensions, ysV, of the polymeric coatings at each temperature were calculated from the contact angles. The temperature coefficients of the surface tensions, dysv/ dT, i.e., the surface entropies, were established for the temperature range covered. I NTRO DUCT10 NThe contact angle and surface tension properties of elastomers and coating materials are known to be important parameters in predicting adhesion. Many industrial processes either require strong adhesion or no adhesion at all. Adhesion to the inner walls of a reactor vessel during polymerization is just one example. Contact angles are readily measured on solid surfaces, and it is generally believed that contact angle measurements is the best approach to the determination of solid surface tensions.The contact angle of a liquid drop on a solid surface is defined by the mechanical equilibrium of the drop under the action of the three interfacial tensions: solid/vapor, ysv, solid/liquid, ysL, and liquid/ vapor, yLv. The equilibrium relation is known as Young's equation:where 8E is the equilibrium contact angle. This equation yields a single, unique contact angle. In practice, however, the contact angle made by an advancing liquid (8,) and that made by a receding liquid (8,) are not identical; almost all of the solid surfaces exhibit contact angle hysteresis (the difference between the advancing and receding contact
Some of the problems and advantages in the use of non‐hydrogel polymers in contact lenses are discussed together with studies on a series of such polymers which have potential advantages over the established material, poly(methyl methacrylate), in that they are both more flexible and more oxygen‐permeable. Of the polymers examined which are all too hydrophobic for direct use, poly(4‐methylpent‐l‐ene) proved to be the most readily modified in such a way that its surface became sufficiently wettable to sustain a coherent tear film without reducing its optical qualities to an unacceptable level. The ‘dissolved’ and ‘gaseous’ oxygen permeability coefficients of this polymer were studied as a function of film thickness, surface hydrophilicity and temperature. A pronounced boundary layer effect was observed in ‘dissolved’ oxygen permeability studies, although this decreased as the surface was treated to make it more wettable (as indicated by the equilibrium advancing water contact angle). The ‘gaseous’ permeability coefficients of oxygen were found to be some 4‐6 times greater than those for nitrogen. A discontinuity corresponding to the glass transition temperature was observed at 28°C with both permeants and apparent activation energies for permeation were determined both above and below this temperature.
The wettability of poly(ethylene terephthalate) films is an important criterion for their industrial use. The attainment of that property is realized by treatment of the material under corona discharge. The purpose of this article is to describe the influence of the principal parameters of the discharge on the modification of the surface properties; the influence was measured by physicochemical methods (ESCA, contact angle). The results prove that the most important physical parameters of the discharge are the wire‐cylinder distance, the current intensity, and the time of treatment. The analysis shows that the fixed species are oxygen and nitrogen in the form of carboxylic functions and amines or nitrogen oxides. In any case, the correlation between free surface energy and concentration of fixed chemical species shows that the surface properties depend on the chemical functions introduced into the material by the discharge.
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