Carbinol- (Hydroxy-) Functional Silicones

The term carbinol refers to a hydroxyl group bound to carbon (C-OH) and is frequently used in silicone chemistry to differentiate them from hydroxyl groups bound to silicon (Si-OH) which are referred to as silanols. Carbinol-terminated siloxanes contain primary hydroxyl groups which are linked to the siloxane backbone by non-hydrolyzable transition groups. Frequently a transition block of ethylene oxide or propylene oxide is used. Carbinol-functional polydimethylsiloxanes may be reacted into polyurethanes, epoxies, polyesters, and phenolics.

Applications include additives for urethane leather finishes and as reactive internal lubricants for polyester fiber melt spinning. They are also utilized as surfactants and processing aids for dispersion of particles in silicone formulations.

Polyethyleneoxide transition blocks are more polar than polypropyleneoxide blocks and maintain a broad range of liquid behavior. Carbinol-terminated siloxanes with caprolactone transition blocks offer a highly polar component which enables compatibility in a variety of thermoplastic resins.

Mono(dicarbinol)-terminated polydimethylsiloxanes are macromers with diol termination on one end of a polydimethylsiloxane chain. In contrast with telechelic carbinol-terminated polydimethylsiloxanes, they have the unique ability to react with isocyanates to form urethanes with pendant silicone groups. In this configuration the mechanical strength of the polyurethane is maintained while properties such as hydrophobicity, release and low dynamic coefficient of friction are achieved. For example, a 2 wt% incorporation of MCR-C61 or MCR-C62 into an aromatic urethane formulation increases water contact angle from 78° to 98°. The reduction of coefficient of friction and increased release of urethanes formulated with diol-terminated macromers has led to their acceptance as additives in synthetic leather.