What is the definition of intumescent material?

Intumescent materials are specifically designed to respond to heat by swelling and expanding when exposed to high temperatures, particularly in the presence of fire. This swelling creates a thick, protective char layer that insulates the underlying material from further heat and flame, thereby enhancing fire resistance. This characteristic makes intumescent materials critically important in fire protection applications, such as coatings for steel structures or plumbing, as they slow the spread of fire and help maintain structural integrity during a fire event.

In contrast, materials that shrink when heated would not provide the necessary fire protection; stable materials at high temperatures may not offer the active protection that intumescent materials do; and materials that ignite easily are not suitable for fire safety applications.