|M.Sc Student||Daniel Beitner|
|Subject||Modifying the Hydrophilic/Hydrophobic Properties of|
PUR Acryl Paints Substrates by ALD and SAMs
|Department||Department of Materials Science and Engineering||Supervisors||Professor Pokroy Boaz|
|Dr. Eric Assouline|
|Full Thesis text|
The modification of polyurethane Acryl paint surface by a combined atomic layer deposition and self-assembling monolayer process was investigated. PUR paint samples were coated with either titanium oxide, aluminum oxide or hafnium oxide, using an ALD process, which can produce very thin and uniform coatings with high precision and control. The aluminum oxide ALD process using trimethylaluminum and water precursors was shown to produce a uniformed coating on PUR paint samples at temperatures as low as 40 °C. Formation of 16-phosphono-hexadecanoic acid SAM on aluminum oxide ALD coated paint samples was achieved using submersion in an ethanol/SAM solution.
The aluminum oxide coating induced an initial large reduction in the contact angle, from 110 ° to 10 °, but the change was not durable - the contact angle returned to its original values within 24 hours of exposure to air. The addition of SAMs, however, induced a durable change: samples coated with SAMs showed an initial decrease of contact angle to 60-70 °, with a further decrease to 25-40° after weathering.
A weather-o-meter was used to test the coatings’ durability, while the contact angle change was measured using an optical tensiometer. The change in the paint hue after coating and weathering was measured using a photo spectrophotometer. The chemical qualities and topography of the ALD coating were examined using environmental scanning electron microscopy and time-of-flight secondary ion mass spectrometry. The SAM growth time and quality were measured both by the change of the wetting angle over time, and via in situ weight gain, utilizing a quartz micro-balance with dissipation monitoring.
These experimental results show that the combination of ALD layers and SAMs can produce durable coatings with modified hydrophilic/hydrophobic properties. The use of SAMs with different end-groups may allow fine-tuning of the wetting properties of the coating.