Curing behavior, thermal, and mechanical properties of epoxy resins cured with a novel liquid crystalline dicarboxylic acid curing agent

A novel di‐carboxylic acid curing agent (DACA) was successfully synthesized and cured with three different epoxy resins: glycidyl end‐capped poly(bisphenol‐A‐co‐epichlorohydrin) (pDGEBA, Mn = 377), N,N‐diglycidyl‐4‐glycidyloxyaniline (TGAP), and 4,4′‐methylenebis(N,N‐diglycidylaniline) (TGDDM). The cured epoxy exhibited excellent thermal stability, which was indicated by high initial degradation temperature (Tid) and char yield. The Tid values of cured epoxy were in the range of 327–338°C, and the char yields increased with increasing epoxy functionality. The char yields of cured DACA/pDGEPA, DACA/TGAP, and DACA/TGDDM samples were 21.1, 60.4, and 66.9%, respectively. In addition, the cured epoxy samples also showed low coefficients of thermal expansion and high storage moduli (E′), which were around 60 ppm/°C and 2800 MPa, respectively. The failure surfaces were ductile and rough, so the cured epoxy samples are expected to have high fracture toughness and impact strength. POLYM. ENG. SCI., 54:695–703, 2014. © 2013 Society of Plastics Engineers