Solid Surface Tension

1776 Words8 Pages
Determination of Solid Surface Tension Using Contact Angle Method de Guzman, J.R., Labarez, K. H., and Yap, J.O. Department of Mining, Metallurgical, and Materials Engineering College of Engineering University of the Philippines Diliman Quezon City 1101, Metro Manila, Philippines Abstract—The objective of this experiment is to determine the solid surface tension of 20:30 ethanol-water, 0.5M NaCl, and distilled water using contact angle method on different solid flat surfaces. The experimental results obtained in this experiment did not align with existing trends. This could be attributed to the molecular and morphological factors that the experimental procedure could not determine. Index Terms—Solid surface tension,…show more content…
This is why data for the sessile drop tests should be collected shortly after the drop forms, and why it is unreliable for heterogenous surfaces [3]. Other methods to measure contact angle are the captive bubble method and the tilting plate method. In the captive bubble method, a needle is immersed in the liquid and rotated. The advantage of this method is that it ensures “that the surface is in contact with a saturated atmosphere,” “minimizes the contamination of the solid-vapor interface from sources such as airborne oil droplets,” and “is much easier to monitor” [3]. In the tilting plate method, a plate instead of a needle rotates to form a meniscus. The technique is less subjective and more accurate. However, both methods require some kind of machine to make them practical. The objective of this experiment is to measure surface tension of different liquids and surfaces using the sessile drop test, where angles can be measured using a digital camera. The aim is to observe behaviors and trends of the effect of different factors, such as concentration of solute, on surface tension, so the sessile drop test is adequate and practical for this…show more content…
The images of the liquid drops are of mediocre resolution; the blurred edge of the liquid makes it difficult to determine the true contact angle. Also, the boundary between the liquid and its reflection is not perfectly clear; this makes it difficult to determine where to begin measuring the contact angle. Another problem is the angle in which some pictures are taken. Being tilted slightly forward, transparent liquid drops adopt the colour of the surface; it is difficult to get an image perfectly perpendicular to the surface without specialized equipment. Since measurement is done by inspection, repeated measurement of a single image may give varying results, it is best if a well-defined image is processed with a program following strict parameters to avoid human

More about Solid Surface Tension

Open Document