A simple methodology for producing super-hydrophobic composite films on various substrates
Various nanoparticles (silicon oxide, tin oxide and aluminium oxide) were mixed with poly (methyl siloxane) (Rhodorsil 224). The mixtures were sprayed on silicon substrates resulting in the formation of a rough, two-length-scaled hierarchical structure surface layer. We report that: (i) Super-hydrophobic composite films were produced with all the particles used, (ii) The effect of the particle's nature on the developed hydrophobicity was examined showing that the maximum static water contact angle is independent of the nature of the polymer-particle binary mixture, (iii) The effect of the particle concentration on the hydrophobic character of the composite film was also examined showing that the static contact angles measured on surfaces which were prepared from dilute dispersions, increase rapidly with particle concentration reaching a maximum value (162±2°) and (iv) When the static contact angle is maximum, the contact angle hysteresis reaches some minimum values (2-4°) providing evidence that the composites prepared with high particle concentration are super hydrophobic and exhibit augmented water repellency. The methodology was also tested on various substrates (glass, marble, concrete, aluminum, silk, wood). The static water contact angle measurements revealed that the substrate has no significant effect on the superhydrophobic character of the applied coatings.