Contact Angle Measurement Reliability Through Washburn Method

This research investigated deionized water contact angle measurement reliability with alumina powder using the Washburn method. This method relates the capillary rise of a liquid through a column of packed powder to the contact angle of the system. A reference liquid that is assumed to be perfectly wetting, such as hexane due to the low surface energy, must be used to compare to the tested liquid. Consistency was hypothesized to be achieved with more powder structure and consistency of packing between reference and test trials. The three types of packing structures explored in this study were unstructured, visually-structured (user tapped), and machine-structured tapping. It was also hypothesized that similar contact angle results would be found for different packing methods of the same powder and liquid. However, the average contact angle for unstructured packing was found to be 32.9°, while the angle for the tapped structure was only 11.7°. This large deviation between types of packing shows that there are more inconsistencies with the use of this method than just the regulation of the packing structure. There were two similar glass chromatography columns used, but the second column experienced an unknown interference that led to a delay in the hexane uptake into the powder, which then led to invalid contact angle calculations. There was no discernible relationship between the packing structure and the standard deviation between trials, so the more structured packing does not seem to affect the consistency of results. It is recommended to perform more experiments on a single packing type with different apparatuses and a narrower particle size range.