There are occasional questions about chemical resistance of silicone, in the sense of whether silicone and in particular silicone rubber can be in contact with certain chemicals without being completely or partially destroyed.
The most common answer is "It depends, can you describe more".
And it does depend. Parameters such as the concentration of the chemical in question, the exposure time and pressure, the ambient temperature and the exposure surface can all have an impact ranging from zero to very high. In particular, there is a big difference between, for example, a silicone adhesive joint being able to withstand being completely immersed in a chemical liquid, or only getting a few drops on it during operation. For example, a gearbox can be sealed with a standard silicone sealant as long as the seal is not completely immersed in the gearbox oil, which is rarely the case.
But to give a little more guidance, you can look at the table below. It shows what happens if a piece of standard quality cured silicone rubber (i.e. silicone adhesive, sealant or gasket, etc.) is fully immersed in a number of chemicals and left there for a week, at room temperature.
The most common impact is that the silicone rubber absorbs the chemical and swells, sometimes quite a lot. In some situations, the change in volume matters, in other situations it does not. Double circle in the table means that the volume change is less than 10 %, which should be acceptable in most cases.
An increase in volume means that several properties of the material change. Elasticity may increase, but the strength tends to go down and so does the hardness. This can degrade the performance of the application.
As the table shows, standard grade silicone is not suitable for sealing petrol, diesel and strong solvents. Instead, you should use fluorosilicone, which I have written about here. If you need good resistance to mineral oils, you can also use silicone adhesives that are specially formulated to cope with it, such as RTV1473.
Do you need help with this? Please contact Tribotec to discuss the matter. We can give tips on which materials work where, and how to test chemical resistance if you are unsure.
