MIL-HDBK-1001/SA
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;
rigidity;
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 (S 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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