INFLUENCE OF OXIDATION TREATMENT OF CARBON POWDERS ON THE CURE KINETICS OF AMINE CURED TETRAFUNCTIONAL EPOXY-RESINS

A tetraglycidyl 4,4'-diaminodiphenylmethane (TGDDM) type tetrafunction al epoxy resin containing carbon powders was cured with the stoichiome tric amount of a tetrafunctional curing agent, namely m-phenylenediami ne (mPDA). Carbon powders were oxidised with air or nitric acid. The i nfluence of carbon powders on curing of the resin was followed by dyna mic mechanical analysis, Fourier transform infrared spectroscopy (FTIR ) and differential scanning calorimetry (DSC). Gelation and vitrificat ion times were determined as a function of the variations of dynamic p roperties. The evolution of viscoelastic modulus during curing of the different mixtures showed that untreated carbon powder clearly acceler ated the kinetics of curing whilst oxidation of carbon powders could r emove their catalysing effect. These results were confirmed by monitor ing the changes in conversion of epoxy and amine groups during cure us ing the FTIR technique. DSC experiments also showed the influence of c arbon powder as a catalyst and the loss of the catalysing effect as a consequence of chemical treatment.