PUR hot melts are commonly available in a slug, cartridge, pails, or drums and are often used for very demanding applications. Common uses of PUR hot melts are: bookbinding, woodworking, automotive, filter applications and product assembly when a structural bond is required. Fast strong adhesion is realized almost immediately but reaches full strength in 24 hours or more. A difference between PUR and all other hot melts is that PUR hot melts cure upon reaction with water drawn from air or substrate. This can be good or bad for cure time based on the amount of moisture content in the air. When uncured PUR hot melt is exposed to moisture, curing begins. While processing, it should be noted that all PUR adhesive exposed to air should be used up as quickly as possible and equipment cleaned immediately if appropriate. Unlike EVA, Metallocene, PE and other hot melts, once heated and exposed to moisture, a PUR cannot be reheated and used.