Wear studies of superhydrophobic coatings of wax sprayed from rapid expansion of supercritical solutions (RESS)
(English)Manuscript (preprint) (Other academic)
The wear resistance of superhydrophobic coatings made by spraying a wax from supercritical carbon dioxide solutions have been evaluated by different methods. Scratch tests were performed by using the tip of the cantilever in an atomic force microscope (AFM) by applying an increasing load force on the tip during the measurement. Compression tests were also performed by applying different loads onto a rubber stamp that was placed on the surfaces. In addition to this, frictional wear was evaluated by moving an index finger over the surface using a device that measured the applied load and frictional forces. The wetting properties of the exposed coatings were subsequently evaluated in terms of advancing and receding water contact angles, the superhydrophobic sliding resistance parameter and the surface roughness (RMS). The morphology of the coatings was studied by scanning electron microscopy and optical profilometry. Scratching, with the AFM, at load forces of 12 nN was enough to fully remove the coating from the underlying silica substrate. Results also show that the surfaces remained superhydrophobic after being exposed to compression loads up to 59 kPa. The frictional wear measurments showed that the superhydrophobic properties were immediately lost after pressing and moving a finger over the coating since the lateral movement destroyed the fine surface structure. Finally it was found that the surfaces could stand up to 200 000 falling water drops without losing its superhydrophobicity.
IdentifiersURN: urn:nbn:se:kth:diva-156401OAI: oai:DiVA.org:kth-156401DiVA: diva2:766505
QS 20142014-11-272014-11-272016-06-02Bibliographically approved