Study of cure kinetics of diglycidyl ether of bisphenol a with Ni(II) and Cu(II) complexes of benzil bisthiosemicarbazone

The curing reaction kinetics of the diglycidyl ether of bisphenol A (DGEBA)-based epoxy and inorganic complexes curing agents based on Ni(II) and Cu(II) chelates with benzil bisthiosemicarbazone LH6 as a ligand was studied using differential scanning calorimetry (DSC). The curing reaction with the ligand and the complexes was characterized by high cure onset and peak maximum temperatures. The kinetics of the curing reaction was evaluated using three kinetic models; Kissinger, Ozawa-Flynn-Wall, and Malek. For the NiLH4 and CuLH4 the average values of E, were calculated to be 82.3 and 116 kJ/mol, respectively. For both complexes, their activation energies at 40 and 30 phr are equal. The values of activation energy (E,), and initial and maximum temperatures of the exothermic curing peak (T-i and T-p) of the ligand are smaller than those of the complexes, and the values of these parameters of the DGEBA/NiLH4 system are lower than those of DGEBA/CuLH4 system. These results indicate the order of reactivity of LH6 > NiLH4 > CuLF4 toward epoxy resin. The effect of hardener concentration, heating rate, and type of metal ion on the cure kinetic parameters and the shape of DSC thermograms were investigated.