Modifications of hydrosiloxane polymers for coating applications

An alternative approach to the formation of resins by hydrolysis-condensation reactions has been developed and evaluated. It combines the use of inexpensive polysiloxanes and transition metal catalysts to easily modify polymers in a one-pot reaction. Polyhydridomethylsiloxane (PHMS) serves as the base polymer, and it can be cured or modified by dehydrocoupling or a combination of hydrosilylation-dehydrocoupling reactions, both catalysed by transition metal catalysts (Pt and Ru). The modified polymers are linear and contain very high mol% of Sl-OH and combinations of Si-OH and Si-OR pendant groups. These groups assist the bonding to surfaces when the modified polymers are deposited as coatings, They then cure by condensation and hydrolysis-condensation reactions, catalysed by both acids and bases. The modified polymers are used for low-temperature paint-like applications, especially where ambient curing is desirable. This article discusses modifications of PHMS for coating applications and describes potential coating applications and typical coating strategies.