Low-Rate Dynamic Contact Angles on Poly(methyl methacrylate) and the Determination of Solid Surface Tensions

✍ Scribed by D.Y. Kwok; A. Leung; C.N.C. Lam; A. Li; R. Wu; A.W. Neumann

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 145 KB
• Volume: 206
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1998.5610

✦ Synopsis

Low-rate dynamic contact angles of nine liquids on a poly-(methyl methacrylate) (PMMA) polymer are measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It is found that two liquids dissolved the polymer on contact. From the experimental contact angles of the other seven polar and nonpolar liquids, it is found that the liquid-vapor surface tension times cosine of the contact angle changes smoothly with the liquid-vapor surface tension (i.e., ␥ l cos depends only on ␥ l for a given solid surface). The dependence of ␥ l cos on ␥ s is explicitly illustrated by replacing the solid surface from the PMMA to other methacrylate polymers: such a procedure shifts the curves in a very regular manner. Thus, because of Young's equation, ␥ sl depends only on ␥ l and ␥ s . This contact angle pattern is in harmony with those from other inert and noninert (polar and nonpolar) surfaces. The solid-vapor surface tension of PMMA calculated from the equation of state approach for solidliquid interfacial tensions is found to be 38.5 mJ/m 2 , with a 95% confidence limit of ؎0.5 mJ/m 2 from the experimental contact angles of the seven liquids.