The hydrophobicity of APTS modified surface decreased quickly under the compact pressure of droplet.
After applying an enough hydraulic pressure, the hydrophobicity could not be restored automatically.
The wettability of APTS modified surface occurs spontaneously in immersion conditions.
The critical pressure of PFO modified surfaces were much smaller than the static energy barrier ΔP.
A modified captive bubble method for determining advancing and receding contact angle is proposed.
We have designed a pressure chamber with a pressure control system to the original experimental.
The modified method overcomes the deviation of the bubble in the traditional captive bubble method.
The modified captive bubble method allows a smaller error from the test.
Fluoropolymer, because of the extremely low surface energy, could be non-stick to water and thus could be a good candidate as anti-icing materials. In this paper, the icephobic properties of a series of fluoropolymer materials including pristine PTFE plates (P-PTFE), sandblasted PTFE plates (SB-PTFE), two PTFE coatings (SNF-1 and SNF-CO1), a fluorinated room-temperature vulcanized silicone rubber coating (F-RTV) and a fluorinated polyurethane coating (F-PU) have been investigated by using SEM, XPS, ice adhesion strength (tensile and shear) tests, and static and dynamic water contact angle analysis. Results show that the fluoropolymer material with a smooth surface can significantly reduce ice adhesion strength but do not show obvious effect in reducing ice accretion at −8 °C. Fluoropolymers with sub-micron surface structures can improve the hydrophobicity at normal temperature. It leads to an efficient reduction in the ice accretion on the surface at −8 °C, due to the superhydrophobicity of the materials. But the hydrophobicity of this surface descends at a low temperature with high humidity. Consequently, once ice layer formed on the surface, the ice adhesion strength enhanced rapidly due to the existence of the sub-micron structures. Ice adhesion strength of fluoropolymers is highly correlated to CA reduction observed when the temperature was changed from 20 °C to −8 °C. This property is associated with the submicron structure on the surface, which allows water condensed in the interspace between the sub-micron protrudes at a low temperature, and leads to a reduced contact angle, as well as a significantly increased ice adhesion strength.
In this work, we have prepared a series of samples with five representative surface wettabilities: i.e. superhydrophilic, hydrophilic, critical, hydrophobic and superhydrophobic. These samples were in situ observed the freezing process of water droplets on clean and artificially contaminated surfaces to investigate the relationship between surface wettability and ice formation. Ice accretion was also tested by spraying supercooled water to samples at different horizontal inclination angles (HIA). Surface topography was proved to be essential to the icing through heterogeneous nucleation. However, the correlation between surface wettability and ice formation was not observed. Finally, we found that the superhydrophobic surface clearly exhibited reduced ice accumulation in the initial stage of ice formation associated with the lower sliding angle (SA) of water droplets.
