Structure, morphology and properties of epoxy networks with dangling chains cured by anhydride

Abstract

A series of epoxy networks containing side aliphatic dangling chains were prepared by the curing reaction of bisphenol F diglycidyl ether (DGEBF), the monofunctional epoxy (including n-butyl, dodecyl, cetyl) and the anhydride. In the cured epoxy networks with the flexible side aliphatic chains, micro-phase separations with different dimension were observed by atomic force microscopy (AFM). Scanning electron microscopy (SEM) measurements implied the presence of a ductile fracture on the fracture surfaces of the modified samples. The result of wide angle X-ray scattering (WAXS) characterization revealed no crystallizations in the modified epoxy resins. Significantly, the nano-sized and submicron-sized phase separations coexisting were observed in the cured E₄-20 (molar ratio of epoxy group between DGEBF and butyl glycidyl ether was 20 : 1). Subsequently, by means of adjusting the length and content of the flexible side aliphatic chains, the mechanical and thermal properties of the cured resins can be tuned in different scales. It was also observed in their dynamic mechanical properties that the storage modulus of modified samples was higher than that of the unmodified sample at glass state regions. Especially, mechanical property tests showed that the cured E₄-20 sample demonstrated excellent mechanical properties with a tensile strength of 98.5 MPa, an elongation at break of 6.1%, and a tensile modulus of 3.1 GPa.