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 MIL-HDBK-1001/5A
Section 7:
SPRAYED POLYURETHANE FOAM
7.1
Material Description. Sprayed polyurethane foam (PUF)
is a field-produced, monolithic plastic foam roof insulation,
produced in the field by nozzle-mixing of two separate liquid
streams, an A (isocyanate) component and a B (hydroxyl or
polyol) component. In addition to these basic chemical
ingredients, the sprayed field mix also requires:
a) a blowing agent (fluorocarbon gas) to form foamed
cells that expand the polyurethane foam resin's volume;
b)
a surfactant to control cell size and cell-wall
c) catalysts to control the reaction rate between the
two chemical components);
d)
fire retardants.
7.2
Uses. Although sprayed polyurethane foam can be used
for new roofs, its major use is in reroofing.
7.2.1
Advantages. Compared with conventional built-up roof
systems, PUF offers the following advantages:
a)
High thermal resistance per unit thickness;
b) Lightweight (roughly 1 psf (5 kilograms per square
meter) for 3-inch (76-millimeter) thick foamed insulation plus
membrane coating);
c) Fast construction (generally two to three times the
rate of conventional bituminous systems);
d) Adaptability to steeply sloped, curved, and other
irregular roof surfaces;
e) Excellent adhesion, capable of producing 3,000 psf
(0.14 Pascal) uplift resistance when placed on a clean, dry,
properly prepared substrate;
f)
Simple flashing details;
g)
System is seamless;
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