Gamma-rays initiated cationic polymerization of epoxy resins and their carbon nanotubes composites

Epoxy resins based on diglycidyl ether of bisphenol A (DGEBA) in the presence cationic initiator in the form of iodonium salt were exposed to gamma-rays in order to initiate curing process. The influence of the initiator concentration, dose rate, chemical structure of monomers and the presence of carbon nanotubes were determined on the basis of the recorded on-line thermal effects. The induction time of radiation curing increased with lowering concentration of the initiator and oxirane groups as well as with decreasing dose rates. As was confirmed by SEM images, carbon nanotubes were uniformly distributed over the matrix and closely surrounded by the macromolecules. Such a structure resulted from adsorption of the initiator on the filler surface what allowed to begin polymerization around nanoparticles and facilitated their incorporation into the matrix. As a consequence, the mechanical properties of the nanocomposites were improved.