What property of intumescent coatings allows them to provide fire protection?

Intumescent coatings are specifically designed to provide fire protection by undergoing a chemical transformation when exposed to high temperatures. The key property that enables this fire protection is their ability to expand when heated.

When an intumescent coating is exposed to fire or extreme heat, it reacts by swelling significantly, forming a thick, insulating char layer. This char layer serves as a barrier that protects the underlying material from the heat of the fire, delaying structural damage and providing valuable time for evacuation and firefighting efforts.

The other aspects listed may pertain to other properties of materials in different contexts, like chemical bonding or water resistance, but they do not directly contribute to the fire protection capabilities associated with intumescent coatings. The expansion upon heat exposure is central to its function as a fire-resistant material, making it the correct choice in this scenario.