Improvements in manufacturability, bonding strength, and curing efficiency of a silicone adhesive

Two-component room temperature vulcanizing silicone adhesive RTV566 with a lower elastic modulus has been widely used in precision optomechanical products such as remote sensors and aerospace infrared cameras. However, the silicone adhesive is of poor manufacturability due to its extremely high viscosity, and the bonded joint usually exhibits low bonding strength and requires a long curing time. This paper investigates a way to improve both the adhesion strength and curing efficiency of Invar alloy and optical glass with RTV566 through single-lap experiments. It is found that adding small amounts of acetone and water can significantly reduce the viscosity, enhance the bonding strength, and shorten the curing time. The viscosity can be reduced by 63.4 % and the bonding strength can be improved by 136.4 % with the weight ratio of adhesive to acetone being 20:2. Moreover, a little amount of water in the weight ratio of 100:10:0.1 (adhesive: acetone: water) can shorten the curing time from 7 days to 4 days without harms to the bonding strength and elastic modulus. As to the mechanism, the silicone adhesive can be dissolved by acetone and its sulfuration reaction can be enhanced by water, resulting in good manufacturability and high curing efficiency. This work contributes a novel and easy-to-use method to greatly improve the performances of the bonding process of precision optical structures.