IMIDAZOLE AND CHROMIUM ACETYLACETONATE AS ADDITIVES FOR THE CURE AND FRACTURE-TOUGHNESS OF EPOXY-RESINS AND THEIR COMPOSITES

The effects of additives such as 2-undecyl-imidazole (C(11)Z) and chro mium acetylacetonate (Cr(acac)(3)) were examined on the curing behavio r and fracture toughness of tetraglycidyldiaminodiphenyl methane/diami nodiphenyl sulphone (TGDDM/DDS) epoxy resins and their composites. The C(11)Z additive alone reacted with TGDDM epoxy resins at about 127 de grees C and increased the resin viscosity, resulting in an acceptable resin content for composite processing. Further addition of Cr(acac)(3 ) to TGDDM/DDS/C(11)Z formulation increased the fracture toughness 5.7 times compared to the typical TGDDM/DDS/BF(3)MEA epoxy formulation us ed for the preparation of laminates. The interlaminar fracture toughne ss of the laminates prepared by TGDDM/DDS/C(11)Z/Cr(acac)(3) formulati on was only twice as much as that prepared by typical TGDDM/DDS/BF(3)M EA. This was due to the fiber bridging contribution to the interlamina r fracture toughness. Based on the experiment, this fiber bridging con tribution was only dependent on the fiber content. Thus, the interlami nar fracture toughness is approximated by the sum of the fracture toug hness of epoxy matrix and the estimated fiber bridging contribution.