Characterization of titanium alkoxide sol–gel systems designed for anti-icing coatings: II. Mass loss kinetics

Abstract

New coatings have been developed that display resistance to the nucleation and adhesion of ice [Simendinger, WH III, Miller, SD, Anti-icing composition. US Patent #6,702,953 2004]. These coatings contain a titanium alkoxide-based sol–gel system designed to facilitate the slow release of tripropylene glycol (TPG) and glycerol, which depress the freezing point of water. The performance and the lifetime of this coating critically depend on the rate at which TPG and glycerol are released to the coating surface. The kinetics and mechanism of this process are studied in this article. Mass loss measurements are reported for temperatures ranging from 22 to 90°C for both the isolated sol–gel and the coating. Two regions of mass loss are observed: loss of isopropyl alcohol, which begins immediately after the reactants are mixed, and loss of TPG and glycerol, which begins at a later time, extending up to several months at low temperatures. Diffusivities and activation energies for IPA and TPG/glycerol in the sol–gel are obtained from 22 to 90°C and compared to similar data obtained for an anti-icing coating containing the dispersed sol–gel. The effect of changing the sol–gel reaction conditions on mass loss kinetics is also reported.