Keywords

fluoropolymer, ultrasonic, hydrophobic, contact angle hysteresis, degradation

Abstract

Many important processes, from manufacture of integrated circuit boards, to an insect’s ability to walk on water, depend on the wetting of liquids on surfaces. Wetting is commonly controlled through material selection, coatings, and/or surface texture. However, wetting is sensitive to environmental conditions. In particular, some hydrophobic fluoropolymer coatings are sensitive to extended water exposure as evidenced by a declining contact angle and increasing contact angle hysteresis. Understanding “degradation” of these coatings is critical to applications that employ them. The durability of a series of fluoropolymer coatings were tested by measuring the contact angle before, during, and after extended submersion of coated glass slides in deionized water. These measurements were compared to similar measurements taken before, during, and after the same coatings were subject to ultrasonic vibration while covered in deionized water. Both methods caused changes in advancing and receding contact angles, but degradation rates of vibrated coatings were significantly increased. Prolonged soaking caused significant decreases in the contact angle of most of the samples, though most experienced significant recovery of hydrophobicity when heat-treated at 160°C after submersion. Some coatings appear noticeably more resistant to degradation by one or both methods. FluoroSyl showed no clear change under submersion, while other coatings experienced significant contact angle change. Degradation of vibrated coatings is inconsistent among coatings, and is not simply an acceleration of the degradation resulting from submerging coatings in water. This is apparent as some coatings are affected by one method but not the other. Atomic force microscopy revealed differing surface effects for different coatings after the coatings were submerged and heat-treated, but the magnitude of this roughness change is insufficient to fully explain the wetting changes. The rate of contact angle degradation was not altered significantly for coatings that were vibrated with acceleration magnitudes between 700 and 7000 g.

Original Publication Citation

Matthew Trapuzzano, Nathan B. Crane, Rasim Guldiken, and Andres Tejada-Martinez, “Wetting Metamorphosis of Hydrophobic Fluoropolymer Coatings Submerged in Water and Ultrasonically Vibrated,” Journal of Coatings Technology Research (JCTR), Published 8/6/2019.

Document Type

Peer-Reviewed Article

Publication Date

2019-08-06

Publisher

Journal of Coating Technology Research

Language

English

College

Ira A. Fulton College of Engineering and Technology

Department

Mechanical Engineering

University Standing at Time of Publication

Full Professor

Share

COinS