Foster® 81-33™ Fire Resistive Adhesive is the preferred adhesive for use with rigid polyurethane insulations. It can be used as a fabricating adhesive in making fittings, as a joint sealer and adhesive in the joints of polyurethane insulation, and as an adhesive to attach insulation to equipment surfaces. Bonds of polyurethane to itself made with Fire Resistive Adhesive are stronger than the base insulation.

Fire Resistive Adhesive withstands continuous surface temperatures up to 300°F (149°C), but it has been subjected to higher temperatures for short intervals with good results. Its excellent resistance to water and high humidity makes it a good sealing compound for joints and seams of insulation on cold water piping and equipment.