Exploring Insulation Materials

June 1, 2012

Polyisocyanurate

Polyisocyanurate
thermal insulation (PIR) is rigid foam insulation, with a closed cell
structure. It is usually manufactured as large rectangular buns, typically 4 ft
wide x 3-24 ft long x 1-2 ft tall, in a range of densities and compressive
strengths. Prior to actual installation, buns are fabricated into various
shapes, including flat boards and preformed pipe half-shells 3-4 ft long,
designed to fit NPS pipe and tubing. Complex shapes can also be fabricated to
fit around valves, fittings, and other equipment. ASTM material specification C
591 covers PIR at service temperatures from -297°F to 300°F. ASTM C 591
contains requirements for density, compressive resistance, thermal
conductivity, water absorption, water vapor permeability, dimensional
stability, closed cell content, and hot-surface performance. This ASTM
specification lists two grades and six types, with the types identifying the
various densities noted below. The most commonly used densities are in the
2-2.5 lb/ft³ range (types IV and II). For comparison purposes, the thermal
conductivity of the Grade 2, Types IV and II PIR, is a maximum of 0.20
Btu•in/(hr•ft²•°F) at 75°F.

The two grades, 1 and 2, identify PIR designed for
different temperature ranges. Grade 1 has a temperature range of -70°F to
300°F; while Grade 2 has a temperature range of -297°F to 300°F.

Key
applications for PIR insulation are on pipe, equipment, tanks, and ducts,
operating at temperatures below ambient. Examples include commercial chilled
water, refrigeration, and liquefied natural gas lines. It is also used as the
core material in the manufacture of foam core panels for various applications,
including transportation, building construction, and temporary shelters.