Toughening of epoxy resins

Abstract

Epoxy resins constitute an important class of thermosets which are used extensively in the field of composites, adhesives surface coatings, etc. They are of aliphatic, cycloaliphatic or aromatic backbones. Epoxy resins based on bisphenol A are commercially available and they have good thermal and mechanical properties. They are cured by a variety of curatives, such as amines and anhydrides, and the mechanism of curing largely depends on the type of curing agent used. They show comparatively low cure shrinkage. Cured epoxies are brittle with poor resistance to crack initiation and growth. Their mechanical properties, in particular toughness, can be modified by incorporating a rubbery phase into the resin matrix. The epoxy matrix can also be modified by various other methods such as incorporation of thermoplastics and particulate fillers. The toughening process leads to improvement in fracture toughness and impact resistance. This review examines the various options and the state-of-the-art vis-à-vis epoxy modification.

Epoxy modified bio-based hyperbranched polyurethane thermosets

“…It is also possible to achieve by physical modification, creating a chemical cross-linking mechanism, blending or via interpenetrating network formation with the other polymers. Epoxy resins are one of the most important classes of thermosetting matrices, which possess good mechanical, thermal, dielectric behavior, low shrinkage during curing, low creep, good adhesive strength, excellent corrosion and weather resistance, good chemical resistance, dimensional stability, wide range of cure schedules and their easy processibilities [9][10][11][12][13]. Polyurethane can be linked to the epoxy network through physical as well as chemical bonding and so it is used to modify polyurethane [14,15].…”

Novel Thermally-Reversible Epoxy-Urethane Networks

“…In general, glycidyl ether epoxy resins can be shynthesized from the condensation reaction of epichlorohydrin and phenol (or alcohol) containing active hydrogen, using two approaches [29][30][31][32]. We synthesized diglycidyl ether monomers (DE) by the cycloaddition DA reaction of 2-furfuryl glycidyl ether to urethane bismaleimides (BMI) (Scheme 1).…”

Thermal Characteristics of Oxazolidone Modified Epoxy Anhydride Blends

“…The epoxy terminated oxazolidone is converted by means of a crosslinking reaction into a three dimensional hard thermoset (Younes, Wartewig, Lellinger, Strehmel, & Strehmel, 1994). The ring opening mechanism governs the reaction between the epoxy and the anhydride (Unnikrishnan, Thachil, & Eby Thomas, 2006). The mechanism of anhydride cure is complex and both etherification and esterification can occur.…”