Polyisocyanurate

Polyisocyanurate (also referred to as PIR, polyiso, or ISO) is a thermoset plastic typically produced as a foam and used as rigid thermal insulation. Its chemistry is similar to polyurethane (PUR) except that the proportion of methylenediphenyl diisocyanate (MDI) is higher and a polyester-derived polyol is used in the reaction instead of a polyether polyol. The resulting chemical structure is significantly different, with the isocyanate groups on the MDI trimerising to form a isocyanurate ring, hence polyisocyanurate.

Production

Polyisocyanurate is produced by a reaction of diisocyanate with a polyol. The reaction mixture is composed of the polyol, a blowing agent, flame retardants, and a catalyst. The reaction is exothermic, and the heat generated causes the blowing agent to evaporate and create small bubbles in the polymer, resulting in a foam.

Properties

Polyisocyanurate is known for its high thermal resistance. It has one of the highest R-value (thermal resistance) ratings of any rigid insulation. Polyisocyanurate insulation is available in a variety of thicknesses and densities. It is light-weight, durable and considerably more fire-resistant than polystyrene.

Applications

Polyisocyanurate is commonly used as a foam insulation in construction, particularly in roofs and walls of commercial buildings. It is also used in the manufacturing of composite doors and in the HVAC industry.

Environmental Impact

Polyisocyanurate is considered to be a more environmentally friendly alternative to some other types of insulation, as it is free of CFCs and HCFCs, which can deplete the ozone layer. However, it is not biodegradable and can contribute to waste in landfills.

See Also

• Polyurethane
• Thermal insulation
• R-value (insulation)

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