Silicones

Silicones cure with moisture in the air and the cure progresses inward from the surface. Curing time increases with the thickness of the sealant section. Thus more moisture in air = faster cure. So, lightly misting the area/air with water will speed fixture because increasing humidity will speed fixture. Heat can actually drive off moisture (if not using a heat/humidity cycle) and prolong cure.

Also consider that the speed of cure of the RTV Silicone can be increased by heat, but this is dependent on part geometry and the substrate. The starting points are as follows: 50˚C to 100˚C at 20% to 90%RH. This may reduce the cure time of an RTV cure silicone from 24 hours to less than 24 hours. Henkel recommends that you test all new adhesive applications under simulated or actual end use conditions to ensure the adhesive meets or exceeds all required product specifications. Since assembly conditions may be critical to adhesive performance, it is also recommended that testing be performed on specimens assembled under simulated or actual production conditions.

Most silicones will bond to most painted surfaces, but paint will not adhere to silicone rubber. Paintinsh should be completed before applying silicones.

Based on the requirements of your application, a 1-part or 2-part adhesive may be more fitting as an adhesive solution.

Due to their unique inorganic structure silicones have an inherent heat resistance far superior to anaerobic, cyanoacrylate, and other organic-based products. This inherent heat resistance allows silicones to have service temperatures of 450°F which can be raised to as high as 600°F with the use of special additives.

Silicone rubber is an elastomer which is a rubbery material that can be stretched and deformed and still return to its original shape. This is an important benefit when bonding two different substrates that will see a wide temperature range during use or experience thermal shock (a rapid temperature change). Due to the elastomeric nature of silicone, it can act as a shock absorber. It can absorb the stresses that result when bonded dissimilar materials undergo thermal shock.

Silicones have good resistance to polar solvents such as coolant, water and isopropyl alcohol. Swelling will occur when silicone rubber is exposed to most hydrocarbon solvents, such as fuel oil and gasoline. However, in alcohol and acetone, the swelling is very low. Water does not cause swelling of silicone. In addition, they have excellent environmental resistance to sunlight, ozone and humidity.