There is no perfect elastomer for all conditions. Considering which material to use depends on how it is used in the application. There is a big difference between immersing the elastomer in some chemical and having some residue on the fingers when operating the keyboard. If there is a residue, the easiest way to handle it is to wipe down the keypad with warm water or mild soap. Therefore, we must look at each application individually.
Silicone elastomer is a good general purpose keypad material.
However, it is not resistant to petroleum oils and is highly permeable to gases. Neither Silicone or Fluorosilicone has good resistance to this fuel. We are considering using the MET M2 series keypad assemblies in an airborne application. Altitude Operating Sea level to 10,000 feet Non-Operating Sea level to 40,000 feet With proper venting to equalize pressure. Since the keypad assemblies when mounted on a panel are sealed to the surface, special factors must be considered.