Epoxy adhesives are generally more resistant to a wide variety of liquid environments than other structural adhesives. However, the resistance to a specific environment is greatly dependent on the type of epoxy curing agent used.
A solid epoxy is one in which a limited reaction between the resin and hardener has been allowed to take place. The resin contains sufficient unreacted functional groups to effect full curing to the thermoset state on subsequent heating.
RESULTING PROPERTIES
The first powder epoxy resin to attract attention was that formed by the reaction of diglycidyl ether bisphenol A (DGEBA) epoxy resins and metaphenylenediamine (MDA). However, under controlled conditions it is possible to form solid epoxy products from a number of bisphenol resins and hardeners.
The above table shows a formulation for an epoxy powder adhesive. Application can be by fluidized bed or electrostatic spray. Cure conditions are 3 min at 204°C or 12 min at 149°C. Shear strength on steel is 3300 psi at room temperature.
