Development of novel metal complexed curing agents for epoxy resins.

A number of novel chloride and acetato complexes, of the type M(PGE-EMI)4X2 where M = Mn, Co, Ni, Cu and Zn and X = Cl and CH3COO-, was successfully prepared and characterised using FTIR, NMR and UV/Vis spectroscopic analysis. The majority of the complexes precipitated as brittle glasses, hence no crystallographic analysis could be carried out to evaluate the exact structure. However, the use of magnetic susceptibility measurements gave an indication of the stereochemistry of the complexes, the majority being octahedral as expected. A thermal dissociation study was undertaken to ascertain whether the complexes were thermally dissociable at elevated temperature. This study was carried out using variable temperature 1H-NMR spectroscopy and showed that the chloride complexes dissociated reversibly whilst the acetato complexes did not (Table 4.1). In order to determine whether these PGE-EMI complexes were effective curing agents in commercial epoxy resins, a kinetic study was carried out at 120°C. The 1H-NMR results in D6-DMSO solution (Table 5.1), showed that by changing the transition metal in the acetato complex series from Copper to Cobalt, the rate constant (k') of the reaction was affected significantly. The Copper acetato complex reacted faster than the corresponding Nickel and Cobalt acetato complexes, hence following the Irving-Williams series of thermal stability. A bulk (solvent free) kinetic study was also carried out (Table 5.2) at 120°C using the acetato metal complexes and showed Nickel acetate to display the fastest rate (for data collected at 100°C) compared with their Copper and Cobalt counterparts at 120°C. The data above 100°C for the Nickel acetato complex appeared to show possible autocatalytic behaviour such that no kinetic parameters could be evaluated