IsoMelt™ HMPUR 5 Clear OB is a long assembly time, moisture-curing, hot-melt polyurethane adhesive that contains optical brightener. The adhesive is solid at ambient temperatures. The adhesive is applied in the molten form and cures in the presence of moisture to form a tough, durable bond. The IsoMelt™ HMPUR 5 bonds to a wide variety of substrates, but at least one substrate must be gas permeable. Typical substrates include wood and wood products, most foams, primed metals, FRP, and other plastics with Dyne levels greater than 38 dynes. At 3-mil thickness, the adhesive transfers to the opposing substrate at least through five minutes of assembly time, prior to nipping.