Reducing the Thermal Aging Effect in Polyisocyanurate Foams



Polyisocyanurate (PIR) foam is a closed-cell, thermoset rigid board insulation that is produced by reacting excess of a polymeric isocyanurate with a polyol in the presence of a blowing agent and other additives. PIR foam provides one of the highest R-value among the conventional buildings insulations. Presence of isocyanurate rings in the PIR structure as a result of cyclotrimerization reaction of isocyanates, leads to improved fire and mechanical properties compared to the polyurethane (PU) foam. These attractive features make PIR foam a versatile and insulation of choice to meet ever increasing energy efficiency, thermal, construction, and fire safety requirements of building codes and regulations. Today, the PIR foam board is a major type of insulation used in the North American low-slope commercial roofs. The PIR boards can be faced with a variety of materials, which include fiberglass, kraft paper, woven polypropylene, steel, plywood, aluminum and cement sheet to suit custom applications.

Research Motivation

Closed-cell PIR foam provides superior R-value compared to the open-cell plastic foams and fiber insulations by entrapping blowing agent gases with a thermal conductivity lower than that of the air in their closed-cells.  However, the thermal performance of closed-cell foams deteriorates with time in a phenomenon known as the “thermal aging”. The thermal aging process in PIR foam is caused by the diffusion of atmospheric gases (mainly N2, O2, water vapor) and blowing agent in and out of the foam cells, respectively. Infusion of air occurs relatively at a much faster rate (typically in first 1-2 years) than the diffusion of blowing agent outwards (typically lasts around 10-20 years). We have been working with industry client(s) to mitigate the thermal aging effect in the PIR foam by modification of the chemistry and addition of nanometric inclusions.


Nitin Shukla, Ph.D.
Senior Technical Staff, Building Enclosures and Materials
Office +1 (617) 714-6519