Polyurethane Adhesives are known for toughness and flexibility even at low temperatures. They have fairly good shear strength and excellent water and humidity resistance. Polyurethane adhesives form strong bonds to rubber, plastics, metal, wood, paper, ceramic, and fabrics. Most types are limited to service temperatures below 80°C.
One-component polyurethane adhesives
consist of isocyanate-containing prepolymers dissolved in a solvent carrier, and reaction with moisture occurs as the solvent evaporates. In order to achieve high adhesive strength and to avoid the formation of bubbles curing is performed under pressure in suitable pressure devices. The curing time can be reduced by adding heat. One-component polyurethanes are used for the construction of sandwich elements of porous materials (wood, polystyrene foam, polyurethane foam and others) and laminated boards (plastics) or metals (aluminum) that are then used in partitioning walls and doors or side walls of caravans and trailers.
Some types of water-borne urethanes are also available, but the newest types of moisture cure urethanes are made in the form of hotmelt adhesives. These are called reactive hotmelts, and exhibit a dual property. They are applied like regular hotmelts, but after application begin to crosslink with moisture to form a tough adhesive layer with high resistance to heat, moisture, and impact
consist of a polyol component (resin) and an isocyanate component (hardener) that must be mixed in a defined ratio prior to application. Important criteria for the users are: the mixing ratio (from 1:1 to 1:10), the pot life (from a few minutes to several hours, depending on the cycle time) and the processing consistency of the adhesive (viscosity from easily pourable to sag resistant).
Two-component polyurethanes are used for large-surface adhesive bonds in vehicle superstructures (sandwich construction), facade elements, ship building and container construction.
are one-component, solvent-free sealants based on moisture cross-linking polyurethanes. They cure to an elastic sealing compound by absorption of moisture from the air. According to their formulation, these masses are pliable to energy-elastic. The maximum admissible permanent movement is 15 - 25%. Polyurethane sealants are paint compatible