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This work presents the preparation of functionalized graphene sheets (FGS)/epoxy coatings cured by cationic photopolymerization with enhanced mechanical properties. The kinetics of the photopolymerization process for formulations up to 1.5 wt% of graphene were evaluated by means of Real-Time FT-IR spectroscopy. The reinforcement of the cured coatings by the graphene was studied by measuring the dynamic mechanical properties and the surface hardness. An increase of almost 40 ºC in the Tg was obtained by adding 1.5 wt% of graphene to the epoxy matrix. A good dispersion state and interaction of the graphene with the matrix were observed by TEM and FE-SEM analyses.

We employed an easy and direct method to measure the thermal conductivity of epoxy in the liquid (nanofluid) and solid (nanocomposite) states using both rodlike and platelet-like carbon-based nanostructures. Comparing the experimental results with the theoretical model, an anomalous enhancement was obtained with multiwall carbon nanotubes, probably due to their layered structure and lowest surface resistance. Puzzling results for functionalized graphene sheet nanocomposites suggest that phonon coupling of the vibrational modes of the graphene and of the polymeric matrix plays a dominant role on the thermal conductivities of the liquid and solid states.PACS: 74.25.fc; 81.05.Qk; 81.07.Pr.

In this work, the effect of several carbon fillers, exfoliated graphite (EG), functionalized graphene sheets (FGS), multi-walled carbon nanotubes (MWCNTs), and oxidized multi-walled carbon nanotubes (f-MWCNTs), were compared on the curing process and physical properties of a cationically photocurable epoxy resin. The extent of the photopolymerization was monitored by Real-Time FTIR spectroscopy. It was found that all the nanofillers induced a delaying of the curing reaction probably due to a shielding effect as well as to an increase of the viscosity by the nanofiller. All the systems showed an electrical percolation threshold, but with MWCNTs was attained at a lower concentration (< 0.1 wt.%). In addition, FGS were the most efficient filler for epoxy resins, deduced by the dynamic mechanical and microindentation measurements. An increase of more than 20 ºC in the glass transition temperature was observed with the addition of 1 wt.% of FGS.

Rigid polyurethane (PU) nanocomposite foams filled with multi-walled carbon nanotubes (MWCNTs), functionalized MWCNTs (f-MWCNTs) and functionalized graphene sheets (FGS) were synthesized by reactive foaming to obtain electromagnetic interference (EMI) shielding materials. Our study indicates that the electrical properties of rigid PU nanocomposite foams are strongly dependent on the foaming evolution, cellular structure and density of these materials, which are themself influenced by the morphology, aspect ratio and surface functionalization of the carbon-based nanofillers. The largest EMI shielding effectiveness was obtained for 0.35 wt% MWCNTs with an electrical conductivity increased of two orders of magnitude ascribed to the formation of a better interconnected network within the systems.