Epoxy Resins essays

Epoxy Resins essays The group of synthetic resins called epoxies produce the strongest adhesives in current use, as well as plastics and corrosion-resistant coatings. Epoxy adhesives are thermosetting; that is, after initial hardening, they cannot be remelted by heat. They have excellent resistance to solvents and weathering agents, and high electrical and temperature resistance. Their adhesion to almost any type of surfaceincluding metal, ceramic, wood, and fabricis unmatched. Epoxies are usually made by reacting epichlorohydrin and Bisphenol A to produce a polymer chain of somewhat complex structure. The end of the polymer chain is an epoxy group from epichlorohydrin; the resulting plastic receives its name from the end epoxy group. The unmodified epoxies are brittle; however, the properties of the cured resin can be varied widely by the selection of a suitable resin, curing agent, filler, and curing procedure. Flexible grades are modified with polyamines and polysulfides. Most epoxy formulations have two components that are mixed for curing. One-component epoxies are available that either contain a latent curing agent or are simply cured by absorption of oxygen from the air. Unlike most thermosetting plastics, epoxies shrink only slightly during curing. Epoxies can be used as filler-adhesives; the strength of the cemented joint is independent of its thickness. The epoxies are used as molding and potting compounds, reinforced plastics, surface finishes, and adhesives. Molding compounds are chiefly used by the electronic and electrical industries; potting compounds are poured to encapsulate small electronic parts. Epoxy paints have outstanding corrosion resistance and are permitted for use on food equipment such as flour bins and can coatings. Large and complex dies for the forming of metal sheet are made of epoxy and are often modified with powdered metal such as aluminum. Uses in construction include the repair and bonding ...