Book excerpt: Unmodified, epoxy resins cause certain problems for both the adhesive formulator and end-user. They are often rigid and brittle; hence, impact resistance and peel strength are poor. For decades, Chemist have been vigorously working to minimize these major shortcomings. Based on a popular course sponsored by the Society of Plastics Engineers and written by an authority in the field, this comprehensive text presents a variety of methods to accomplish what up to now has been a formidable task. Beginning with epoxy chemistry, moving on to fillers, filler treatments, and surfactants, and ending with current and future development in formulating Epoxy Adhesives, this rigorous text addressed the problem of improving flexibility, durability and strength by adding chemical groups to the epoxy structure either via the base resin or the curing agent or by adding separate flexibilizing resins to the formulation to create an epoxy-hybrid adhesive.