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Epoxy resins 'physical and chemical characteristics
Secondary hydroxyl groups and epoxy groups are present in epoxy resins, which add to their remarkable reactivity and versatility. Due to the polyurethane adhesives 'secondary hydroxyl groups' ability to react with isocyanates, epoxy resins can be used as polyol components. However, only the hydroxyl groups are present in these reactions, leaving the epoxy groups out.
Through a variety of chemical reactions, epoxy resins can be modified to improve their performance. For instance,
Acid-catalyzed ring-opening reactions In polyurethane adhesives, the carboxyl groups of acidic resins can open the epoxy ring, allowing for further reactions with isocyanates.
Epoxy resin modification by combining phosphoric acid with ethyl acetate in a heated reaction with phosphoric acid can result in adducts that enhance polyurethane adhesives 'initial adhesion, thermal resistance, and hydrolytic stability.
Amine modification Polyols are produced when reacting epoxy resins with alcohols or amines, and the inclusion of tertiary nitrogen atoms in the adducts speeds up the reaction with isocyanates.