Amine cured epoxide networks: Formation, structure, and properties

Various types of epoxide-amine networks based on diglycidyl ether of Bisphe nol A (DGEBA), diglycidylaniline (DGA), or TGDDM were prepared, and the eff ect of the reaction mechanism on network formation, its structure, and prop erties was investigated. Structure evolution was followed, and fraction of the sol, equilibrium rubbery modulus, and glass transition temperature of n onstoichiometric networks were determined as a function of composition. Sho rt-range cyclization was proved to be the main factor governing formation a nd structure of DGA-based networks, resulting in a nonnegligible sol fracti on of the stoichiometric system. In contrast, the substitution effect in am ine determines the structure evolution in the DGEBA-diamine networks. A the oretical model for formation of DGA-amine networks was developed, taking in to account the full complexity of the reaction mechanism: cyclization, inte rdependent reactivity of epoxy and amine groups, homopolymerization by ethe rification, and ionic polymerization as well as formation of reactive inter mediates. A reasonable agreement with experimental data in both amine and e poxide excess was obtained.