Low moisture absorptive epoxy formulations for Gr/Ep laminates

Abstract The incorporation of 2‐undecyl‐imidazole (C₁₁Z) and chromium acetylacetonate (Cr(acac)₃) additives into N, N, N′, N′‐tetraglycidyl diaminodiphenylmethane (TGDDM)/diaminodiphenylsulfone (DDS) epoxy formulations was found to significantly decrease the moisture absorption of their prepared graphite/epoxy laminates. However, the same additions did not much affect the moisture absorption of the cured TGDDM/DDS neat resins. Thus, the former case was attributed to the processing effects in view of the fact that C₁₁Z pre‐reacting with TGDDM during lay‐up process produced the ether‐linkage polymer chains in the epoxy networks and raised the viscosity. The following compacting stage of laminates was believed to squeeze the small molecules such as unreacted TGDDM, DDS and Cr(acac)₃, toward the surface of carbon fibers and increase the chance of Cr(acac)₃ to block the hydroxyl groups in the epoxy networks produced by the reactions between TGDDM and DDS. Some evidence was provided to support the above hypothesis in this study.