ISOTHERMAL CURING BEHAVIORS OF EPOXY/GRAPHITE OXIDES NANOCOMPOSITES

Abstract

The cure kinetics of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane(TGDDM) and 4,4′-diaminodiphenylsulphone(DDS) nanocomposites filled with graphite oxide(GO) was studied by isothermal differential scanning calorimetry(DSC).Furthermore,the functional groups on the surface of GO and their influence on the cure behaviors of TGDDM/DDS/GO nanocomposites were studied by X-ray photoelectron spectroscopy(XPS) and Fourier-transform infrared spectroscopy(FTIR),and the thermal stabilities of the neat graphite and GO were compared by thermalgravitimetric analysis(TGA).The XPS,FT-IR and TGA results showed that there were large numbers of polar functional groups such as hydroxyl,carboxyl and cyclic epoxide groups on the surface of GO,which effected the cure behaviors of TGDDM/DDS/GO nanocomposites.The experimental data of the isothermal DSC for both the neat TGDDM/DDS system and its GO nanocomposites showed an autocatalytic behavior.Furthermore,with the increase of GO contents,the time to the maximum cure rate decreased whereas the initial cure rate increased with the increase of GO contents,which indicated that GO catalyzed the cure reaction of epoxy.The apparent activation energy for the initial stage of the reaction(E1) of TGDDM/DDS/GO nanocomposites obtained by Kamal's model decreased first and then increased with the increase of GO contents,while the apparent activation energy for the reaction after the initial autocatalytic stage(E2) slight decreased with the increase of GO contents.Good agreement between the experimental data and the autocatalytic model with the modified diffusion factor in the later stage of cure was found over the whole curing temperature range for all of the neat epoxy resin and its nanocomposites with GO.The results showed that the incorporation of GO accelerated the cure reaction of the TGDDM/DDS system at lower GO content due to the interaction between the functional groups on the surface of GO and the epoxy resin.