Originally Aired - Wednesday, September 11 • 4:00 PM - 4:25 PM
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Location: 1B
Title: Replacing Water Break Testing for Objective and Quantitative Control of Coating and Bonding Processes
Description: Coating processes, such as painting, form a bond between the paint and the first few molecular layers of the material being coated. Small amounts of contaminants can cause visual defects and loss of durability or performance in the finished product. It is crucial to understand the condition of the surface that is being coated. The historical qualification method for many coating procedures has been the water break test. In this test a surface is dipped in or sprayed with water, and the behavior of the water on the surface is observed by a technician. If the water remains a smooth sheet over the surface, then the part passes the test. If the water breaks (beads up) on the surface, then the part fails the test. This method of qualification is subjective, depending on the technician to determine if the amount of water break is within scope. Water break also does not have the resolution required for materials that must have very high surface energies for successful coating. The limitations of the water break test can lead to both false positives (bad parts being accepted) and false negatives (good parts being rejected). Many industries would benefit from a replacement for the water break test that is quantifiable, objective, and non-destructive. In this work the water break test is compared to water contact angle analysis on composite and metal samples with various levels of contamination and treatment. Aluminum samples were contaminated via spin coating with varying amounts of silicone. Contamination levels were verified using Fourier transform infrared spectroscopy. Composite samples underwent atmospheric plasma treatment to increase surface energy. Contaminated and treated sample surfaces were qualified with water break test (ASTM F22) and water contact angle analysis. Contact angles that correlated to the transition from a water break free to a water break surface correspond to surfaces that were marginal in terms of cleanliness, surface energy, and bondability.
Type: Technical Paper
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