What is it about?
As known de-icing methods use a high amount of energy or environmentally harmful chemicals (e.g. for aircraft), this article focuses on the water wettability and ice adhesion on functional PU film surfaces in development towards an improved removal of ice (de-icing) or a reduced formation of it (anti-icing). Inspired by the Lotus plant leaf, a “superhydrophobic” surface can be produced by the combination of a hierarchical micro/nanoscale roughness and a hydrophobic surface coating. By a hot stamping process, we have generated differently shaped microstructures (circular and elliptical cones) on polyurethane (PU) films which were afterward coated by a plasma-enhanced chemical vapor deposition (PECVD) process with thin, hydrophobic fluorocarbon films.
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Why is it important?
PU films are suitable for outdoor use because they are resistant to erosion and UV radiation. The films can be glued to different geometries and can easily be exchanged if damaged. This combination of microstructuring and plasma processes could be suitable for a roll-to-roll process for the functionalization of large-area functionalized polymer films. The water contact angle (CA) measurements show the water repellency of the plasma coatings (advancing CA = approx. 120°), the hydrophobicity could be further improved by microstructuring (advancing CA = approx. 150°). Very small contact angle hystereses of around 1° to 3° were measured, which enables an easy roll-off of water drops. For determination of the ice adhesion force small water droplets were frozen on the produced surfaces and the force for removal was then measured by pull-off tests. The results show a reduced ice adhesion for some of the functional surfaces, especially the flat PU films.
Perspectives
The water contact angle measurements show that superhydrophobic PU surfaces can be created by hot embossing and plasma processes, and these processes could enable a large-scale roll-to-roll functionalization of superhydrophobic polymer films. However, the theory on superhydrophobicity and the measurement results regarding the ice adhesion are outdated and do not withstand newer research findings of both our group as well as other groups. For energy-efficient de-icing and low ice adhesion, the PU film surface functionalization should be further optimized.
Dr. Philipp Grimmer
Universitat Stuttgart
Read the Original
This page is a summary of: Energy Efficient De-Icing by Superhydrophobic and Icephobic Polyurethane Films Created by Microstructuringand Plasma-Coating, June 2015, SAE International,
DOI: 10.4271/2015-01-2159.
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