Adhesives Setting by Polycondensation

Polycondensation adhesives include phenolic and resorcinol resins and also urea -and melamine-formaldehyde resins. Adhesives of particularly high quality are obtained by combining phenolic resins with polyfvinyl formal) resins, nitrile rubber, or epoxy resins. Combinations such as these are often marketed as adhesive film. 

Trade Names. In Germany Redux, Tegofilm, Kaurit, Pressal. 

Phenolics or phenol-formaldehyde structural adhesives are chemically reactive systems that cure to form thermosets. In one-component systems, meltable powders (resols) are used as binders for particle board or as alloys (including nitrile-phenolics, vinyl - phenolics, and epoxy-phenolics), which are used in the structural bonding of metals. In two-component systems, the resin and catalyst are mixed and then heated to initiate curing. Both systems cure by a condensation reaction that produces a byproduct. 

Phenolics dominate the wood adhesives market, especially for plywood. The structural adhesive bonding of metals, particularly with phenolic alloys, is another application. 

Vinyl-phenolics are alloys composed of polyvinyl formal (PVF) - phenolics or polyvinyl butyral (PVB)-phenolics. They are available as liquids and films. In general, vinyl-phenolics have a maximum service temperature of SOT and are equal to phenolic - nitriles in strength. These adhesives are better than epoxies in sandwich structures that require high strength. 

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