What is a sealant?

A sealant is an elastomeric material that allows for 25% to 50% movement. Sealant is used to fill gaps, to keep water and air at bay, to allow for expansion and contraction of building materials, and to enhance aesthetics. Silicone and polyurethane are two popular types of sealant. Despite their common purpose, there are a few major differences between them.

A Lesson in Chemistry

The primary difference is at the chemical level. Polyurethane is an organic material. Silicone is an inorganic material. The effects of breakdown of silicone and polyurethane depend on the sealant’s chemical makeup.

Why is sealant chemistry important? – UV Stability and Reversion

At this point you may be asking yourself, “why is sealant chemistry important?” It comes down to how the chemistry of each type of sealant performs on a building when it is exposed to UV rays from the sun. In the presence of UV light, an organic material (polyurethane) will eventually revert to its natural state, thus changing properties and deteriorating over time. An inorganic material (silicone) will not.