ABSTRACT
Phenolic resins can be bonding agents as neat resin (adhesive) or as part of a formulation (phenolic modifier). The phenolics have good adhesion to polar substrates, good high-temperature properties, resistance to burning, and high strength. Phenolic modifiers are a smaller subset of the general category of phenolic adhesives. There are general types of phenolic modifiers distinguished by whether the phenolic resin functions in the adhesive formulation primarily as a tackifier or as a cross-linking agent. Resols or hexa-modified, novolac phenolic resins are used in structural adhesives. They function primarily as crosslinking components rather than as tackifiers, as is the case with most elastomer-based adhesives. Combinations of epoxy and phenolic resins provide structural adhesives with superior high-temperature resistance in comparison to phenolic-modified vinyl or nitrile-based systems. Phenolic resins have been used widely as modifiers to improve the tack, specific adhesion, bond strength, and heat resistance of elastomeric adhesives.
