Adhesives Setting by Polyaddition

Epoxy resin Adhesives. Epoxies [47], [48] are among the most widely used structural adhesives. These chemically reactive systems include two-component systems that cure at room temperature or elevated temperature and one-component systems, which usually require heat for curing. 

Epoxy thermoset adhesives, available in many formulations, can be used to join most materials. These adhesives have good strength, do not emit volatile substances during curing, and have low shrinkage. However, peel strength and flexibility are low, and epoxies are brittle. 

A typical two-component system consists of a resin and a hardener, which are packaged separately. In a one-component system, the resin and hardener are packaged together. Other possible additives include accelerators, reactive diluents, plasticizers, resin modifiers, and fillers. 

The most common epoxy resin is based on the diglycidyl ether of bisphenol A. Epoxy resins are sometimes esterified with fatty acids or modified with polyurethane intermediate chains for elastification. 

The hardeners used for hot-setting formulations, i.e., for hardening temperatures above 100°C, are preferably dicarboxylic acid anhydrides, dicyandiamide, and certain aromatic amines. The hardening temperatures, which are normally in the range 150-200°C, can be lowered by adding accelerants [49]. 

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