Polyisocyanurate

Polyisocyanurate (/ˌpɒlɪˌaɪsoʊsaɪˈænjʊəreɪt/), also referred to as PIR, polyol, or ISO, is a thermoset plastic[1] typically produced as a foam and used as rigid thermal insulation.

At these elevated temperatures and in the presence of specific catalysts, MDI will first react with itself, producing a stiff, ring molecule, which is a reactive intermediate (a tri-isocyanate isocyanurate compound).

Remaining MDI and the tri-isocyanate react with polyol to form a complex poly(urethane-isocyanurate) polymer (hence the use of the abbreviation PUI as an alternative to PIR), which is foamed in the presence of a suitable blowing agent.

As such PIR manufacturers can offer multiple products with identical densities but different indices in an attempt to achieve optimal end use performance.

[3] PIR foam panels laminated with pure embossed aluminium foil are used for fabrication of pre-insulated duct that is used for heating, ventilation and air conditioning systems.

[11] PIR insulation board (cited as the FR4000 and the FR5000 products of Celotex, a Saint-Gobain company)[12] was proposed to be used externally in the refurbishment of Grenfell Tower, London, with vertical and horizontal runs of 100 mm and 150 mm thickness respectively;[13] subsequently "Ipswich firm Celotex confirmed it provided insulation materials for the refurbishment.