Cure kinetics and ultimate properties of a tetrafunctional epoxy resin toughened by a perfluoro-ether oligomer

A commercial grade of a tetrafunctional epoxy resin (TGDDM) has been modified by the addition of a perfluoro-ether oligomer to improve the toughness. The cure characteristics of a typical composition of this mixture have been investigated by in situ FT-NIR spectroscopy. It has been found that the presence of the fluoro-oligomer induces a two-fold reduction of the initial curing rate, which has been discussed in terms of the cure mechanism. For all the investigated compositions, the final conversion of the reactants did not change with respect to that of the unmodified resin. The phase structure of this system has been investigated by dynamic-mechanical analysis and by scanning electron microscopy. Both these techniques showed no evidence of a two-phase morphology. Finally, the fracture parameter Gc has been found to increase significantly for concentrations of the modifier exceeding 10 parts by weight.