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. Thixotropic agents are used to provide non-sag properties. At one time asbestos fiber was used as the main thixotrope; however, today this has been replaced by other fibrous fillers such as cellulose fiber.
RESULTING PROPERTIES
The above table shows a comparison of properties using fumed silica and cellulose fibers in a 1K, elevated temperature curing epoxy adhesive formulation. Note that a certain percentage of fumed silica is still required in the cellulose fiber filled formulations for optimal non-sag properties. The cellulose fibers’ low specific gravity (1.1) relative to other filler materials also contribute to weight savings that further improves the sag resistance of these systems.
