The network structure and properties of multifunctional epoxy/anhydride systems

In this study, bi-, tri-, and tetra-functional epoxy systems were chosen to design network structures using hexahydrophthalic anhydride as curing agent and tris-(dimethylaminomethyl) phenol as accelerant with bifunctional 1,4-butanediol diglycidyl ether as the flexible reactive diluents to further adjust the network structure. The cross-link density and activation energy (E_a) of glass transition were calculated by dynamic mechanical thermal analysis (DMTA) data. The packing of molecular chain and average distance between molecular chains were analyzed by DMTA and X-ray diffraction measurements, respectively. As a result, the loss modulus, glass transition temperature (T_g), cross-link density, average distance between molecular chains and E_a were found to be positively correlated with the degree of functionality. Meanwhile, the storage modulus of cured epoxy products at glass state was found to vary as follows: diglycidyl ether of bisphenol F (DGEBF) > tetraglycidyl diaminodiphenylmethane > triglycidyl-p-aminophenol (TGPAP). The loading of diluents decreased T_g and E_a and increased the storage modulus at glass state of DGEBF and TGPAP systems.