This sponge-like polyurethane foam expands to several times its size when exposed to open flames or high heat (above 300°C). The heated foam forms a solid char, which resists further heat degradation.
Expanding intumescent materials are used for seals that rapidly close off the passage of fire, smoke, and toxic gases during a fire. It is used for doors, ventilation ducts, and pipe and cable lead-ins. It can be packed around plastic piping, where it fills out the vacant space left when pipes burn and melt during a fire.
The foam is easily cut to the desired shapes and sizes, and it can be painted after installation. The active ingredient in this intumescent material is "expandable graphite", which in its undiluted state expands hundredfolds when heated.
Use intumescent materials in machine construction to isolate a fire inside the machine.
The sample measures minimum 40 mm x 40 mm x 40 mm.
Burn the sample to see it expand. You can see the black expandable graphite flakes
in the foam.