This work aimed to produce graphene oxide with few graphene layers, a low number of defects, good conductivity and reasonable amount of oxygen, adequate for use as filler in polymeric composites. Two starting materials were evaluated: expanded graphite and graphite flakes. The method of oxidation used was the Staudenmaier one, which was tested over different lengths of time. No appreciable differences were found among the oxidation times and so the lowest oxidation time (24 h) was chosen as the most adequate. An investigation was also conducted into suitable temperatures for the reduction of graphite oxide. A temperature of 1000 ºC gave the best results, allowing a good quality material with few defects to be obtained. The reduction was also evaluated under inert and normal atmosphere. The best results were obtained when the least modified material, e. g., graphite flakes, was used as a starting material, oxidized for 24h and reduced at 1000 ºC for 30 s in a quartz ampoule under a normal atmosphere.

Artículo de publicación ISIThe use of graphite and polyolefins as starting materials to prepare nanocomposites is convenient because both are inexpensive and have very different properties, one is conductive and the other is insulating. The formation of nanocomposites can extend the applicability of both commodities. In this work we synthesized nanocomposites of polyethylene (PE) with two types of graphites, graphite oxide (GO) and reduced graphite oxide (RGO), by in situ polymerization using a supported metallocene catalyst. The functional groups on the graphites were used to support the metallocene catalyst by a previous treatment with methylaluminoxane. The nanocomposites were obtained with good catalytic activities and presented excellent morphology and dispersion; their elastic modulus and crystallization temperatures were higher than those of neat PE. However, the nanocomposites PEGO were insulant, whereas PERGO had a conductivity of 1.1 x 10(-5) S cm(-1) with 3.1 wt% filler. This is a significant result compared to the conductivity obtained using non-supported graphite nanosheets where more than 15 wt% of graphite nanosheets are needed to obtain conductivities higher than 10(-7) S cm(-1). This improvement in the percolation threshold was attributed to the good morphology of the PERGO nanocomposites obtained due to the control of the graphitic sheets and the support methodology.CNPq 302902/2013-9 473128/2011-0 FAPERG-PRONEX 09/2009 Department of the Navy Grant N62909-11-1-7069 Millennium Nucleus of Chemical Processes and Catalysis (CPC) NC12008

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