Preparation of hyperbranched epoxy resin containing nitrogen heterocycle and its toughened and reinforced composites

Low‐viscosity hyperbranched epoxy resin‐containing nitrogen heterocycle (HTPE) is synthesized from epichlorohydrin (ECH), dimethylol propionic acid (DMPA), and tris(2‐hydrooxyethyl)‐isocyanurate. The structure and properties of HTPE are characterized by FTIR, GPC, and molecular simulation. The performance of HTPE/diglycidyl ether of bisphenol‐A (DGEBA) composites first increase and then decrease with the increase of the content and molecular weight of HTPE. Compared to those of pure DGEBA, the impact strength, fracture toughness, tensile, and flexural strength of HTPE‐2/DGEBA composite can be enhanced by about 192%, 39%, 18%, and 23%, respectively. The absence of microphase separation and the presence of lots of “protonema” on the fracture surface of the composites are explicated by an in situ reinforcing and toughening mechanism. The intramolecular cavity of HTPE and the strong interaction between HTPE and DGEBA are two key factors to toughening and reinforcing DGEBA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012