Polyimide

Polyimide
(PI) insulation is defined by ASTM as lightweight, flexible, open-cell foam for
use as thermal and sound-absorbing insulation in commercial and industrial
environments. PI is manufactured as large rectangular buns, typically 4 ft wide
x 8 ft long x 5-30 inches tall, in a range of densities. Prior to actual
installation, buns are fabricated into various shapes, including flat sheets
and preformed pipe half-shells designed to fit over NPS pipe and tubing.
Complex shapes also can be fabricated to fit tightly around fittings, elbows,
and other equipment. ASTM material specification C 1482 covers PI insulation at
service temperatures from -328°F to +572°F.

ASTM
C1482 defines the requirements for density, thermal conductivity, acoustic
absorption, thermal stability, flammability, smoke density, smoke toxicity,
chemical resistance, corrosiveness, and mechanical properties. This ASTM spec
lists two grades and four types of PI foam, but the following three types are
most commonly used for commercial and industrial applications.

Key
applications for PI foam include thermal and acoustic insulation for HVAC and
industrial equipment, acoustic duct liner, high temperature pipe insulation,
and expansion joints for cryogenic facilities.

The
use of an appropriate vapor retarder is required in all applications where
condensation could occur. There are a wide variety of vapor retarders, both
films and coatings, that can be specified.

Figure 1