Wettability and Anti-icing Properties of Slippery Liquid Infused Porous Surfaces
Permanent address of the item is
Lubrikantti-impregnoitujen huokoisten pintojen kastuvuus- ja jäätymättömyysominaisuudet
Nature has provided intriguing possibilities to tackle wetting and to some extent even icing. By capturing the unique and inventive structures, novel surfaces with low wettability and low adhesion to ice are being under research. After deliberate material selection, these surfaces would provide easement to many industries suffering from ice accretion. In the Arctic region, buildings, wind turbines, maritime vessels, aviation and other transportation operators could benefit surfaces with anti-ice or ice-repellent properties. The aim of this master’s thesis was to study slippery liquid infused porous surfaces, SLIPS, by selecting proper porous solid and water immiscible lubricant combinations. The focus was in finding a surface which would have low ice adhesion and good anti-wetting properties with low lubricant evaporation. Different lubricants and oils with altered viscosities, were used in the tests as they naturally repel water. As a porous solid material, polytetrafluoroethylene (PTFE) –membrane was used to impregnate the lubricant into. The membranes had altering pore sizes and were manufactured by two different companies. Since PTFE is also water-repellent, that is hydrophobic, the produced SLIPS surfaces functioned in wettability tests as expected. From the fabricated SLIPS, the evaporation was examined as to its effects on wettability of the surface. The wettability was observed as a function of time as static contact angle, contact angle hysteresis and sliding angle tests were performed to the SLIPS. From the evaporation and wettability tests, the most promising and interesting SLIPS –samples were selected to the cyclic ice adhesion test. The cyclic ice adhesion test encompassed ice accretion in icing wind tunnel, ice adhesion measurement with centrifugal machinery and wettability tests afore next cycle. It was noticed that different pore sizes in the membranes had effects on wettability, but more significantly on ice adhesion strength. Moreover, when the results of the work are reviewed, submicrometer pore sizes were superior to micrometer pore sizes, as the ice detached from them more easily. It was detected that different lubricants had altering evaporation rates but also differenced in wettability experiments. Altogether, more cyclic ice adhesion testing is needed to perform in order to gain better comprehension towards SLIPS lifespan in icing and de-icing cycles. In addition, more lubricant and porous solid pairs are needed to tests to yield good performance SLIPS with exceptionally low ice adhesion strength.