polyiso

Polyiso, short for polyisocyanurate, is a rigid foam plastic used primarily as insulation in buildings and other applications. It is produced by reacting a polyol with methylene diphenyl diisocyanate and a blowing agent to form a crosslinked closed-cell network with isocyanurate linkages. The resulting material is lightweight and available as boards, sprayed foams, or composite panels, often faced with aluminum foil, paper, or fiberglass to improve fire performance and moisture control.

Thermal performance is a key attribute. Polyiso typically offers an R-value of about 6.5 to 7.0 per inch (in imperial units) and a thermal conductivity around 0.025 W/m·K, making it one of the most efficient insulation materials by thickness. Its closed-cell structure provides relatively low water vapor permeability and good dimensional stability, though moisture exposure and damage can affect performance if barriers are compromised. Installation quality, including proper sealing and air barriers, is important to maximize effectiveness.

Common applications include exterior and interior wall insulation, roof and attic insulation, and insulated panels for cold storage. It is also used in some sandwich panels and as a component of multidensity or faced products designed for specific building assemblies.

Safety, fire, and environmental considerations are important. Polyiso is combustible and must meet fire-safety requirements for its installed use; facings and coatings influence flame spread and smoke development. Production and handling involve isocyanates, so appropriate ventilation and protective equipment are necessary. Blowing agents have evolved to lower global warming potential, but environmental impact depends on formulation and end-of-life management.

Standards and regulation typically reference ASTM C578 for polyiso insulation boards, along with related standards for sprays, facings, and assemblies. See also polyurethane, insulation materials, and building envelope design.