Highly Durable Superhydrophobic, Oleophobic and Anti-Icing Coatings and Methods and Compositions for Their Preparation

A method of preparing a coating on a substrate comprising:

• a) applying to said substrate a coating composition comprising i) a binder and ii) first particles having a size of about 30 microns to about 225 microns, to provide a base coating;
• and
• b) applying to said base coating a composition comprising second particles
• wherein
• i) the second particles have been treated with polydimethylsiloxane or hexamethyldisilazane prior to the application of the second particles to the base coating, or
• ii) the second particles comprise one or more moieties independently selected from the group consisting of cycloalkyl optionally substituted with one or more fluorine atoms, alkyl, haloalkyl and perfluoroalkyl moieties, which one or more moieties are covalently bound to said second particles by reaction of particles with a silanizing agent of formula (I) prior to the application of the second particles to the base coating, said compound of formula (I) having the structure:
• R4-nSi—Xn (I)
• where
• n is an integer from 1 to 3;
• each R is independently selected from
• (i) alkyl or cycloalkyl group optionally substituted with one or more fluorine atoms;
• (ii) C1 to 20 alkyl optionally substituted with one or more fluorine atoms;
• (iii) —Z—((CF2)q(CF3))r, wherein Z is a C1-12 divalent alkane radical or a C2-12 divalent alkene or alkyne radical, q is an integer from 1 to 12, and r is an integer from 1-4;
• each X is independently selected from the group consisting of —H, —Cl, —I, —Br, —OH, —OR2, NHR3, and —N(R3)2;
• each R2 is an independently selected C1 to 4 alkyl or haloalkyl group;
• and
• each R3 is an independently selected H, C1 to 4 alkyl or haloalkyl group;
• and
• wherein the coating has a surface in contact with the substrate and an exposed surface that is not in contact with the substrate, the exposed surface having an arithmetical mean roughness from about 0.2 microns to about 20 microns or a ten point mean roughness from about 1 micron to about 90 microns, or about 7 micron to about 100 microns, and wherein the coating has a greater number of second particles on the exposed surface than on the surface in contact with the substrate.