Intumescence (Latin: intumescencia, from tumor - swelling) denotes an expansion or swelling, i.e. an increase in volume of a solid body without chemical conversion.
In fire protection, the term describes the appropriate "swelling" or foaming of materials. Intumescent building materials increase in volume and correspondingly decrease in density when exposed to heat . As a rule, intumescent materials are used in preventive structural fire protection, where they can perform the following tasks:
- Foam to form a light insulation layer as a heat brake. Expandable graphite ( expandable graphite ), for example, releases gases when exposed to heat. For example, if it is added to the insulating jacket of an electrical line, it forms a "foamed" layer of ash with the incinerating insulating material , which hinders the supply of oxygen - and thus the spread of the flame.
- Endothermic cooling through evaporating crystal water (hydrates); z. B. in building materials made of gypsum
- Formation of a fire protection bulkhead through expansion pressure, e.g. B. when filling the cavity, the a-melting plastic - pipe leaves in a wall or ceiling opening.
Intumescent building materials are also called "intumescent layers". In Germany , intumescent building materials, the building products they contain and the types of construction made with them are subject to approval.
→ see main article fire protection coating
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