(360g) Cationic Cure Kinetics of a Polyoxometalate Loaded Epoxy Nanocomposite

In this paper, results of the cure reaction kinetics and resulting glass transition temperature of phosphotungstate (PTA) loaded epoxy nanocomposites are presented.  PTA is a 1 nm size particle composed of a tungsten oxide shell and a phosphate group at the core and is part of a class of metal oxides called polyoxometalates.  PTA is dispersed in the epoxy resin up to volume fractions of 0.1.  Differential scanning calorimetry measurements show the cure of the epoxy resin to be sensitive to the amount of PTA.  A kinetics study of the cure exotherm suggests that PTA acts as a catalyst promoting cationic homopolymerization of the epoxy resin.   A cure mechanism based on cationic propagation and termination reactions is proposed.  High resolution TEM images of the cured epoxy nanocomposite show the PTA to be well dispersed in the epoxy matrix.  Dynamic mechanical temperature sweep measurement show a reduction in the glass transition temperature of the cured nanocomposite as the PTA loading is increased.