In general most RTV sealant compounds are silcone based and do not bond to all materials. This is especially true with some non-metallic materials i.e.polyethylene, teflon, etc. It is important that the mutual surfaces to be sealed are clean and free of oil. Brake cleaner or alcohol are good solvents to use before applying the RTV. If the sealing aplication involves high pressure it is important to let the RTV fully cure before applying pressure. RTV is the acronym for room temperature vulcanizing. Complete curing of these sealants usually requires at minimum 12-24 hours. There are applications where non-hardening type sealants perform better than the RTV type.