Síntese e caracterização de compósitos nanoestruturados a base de nanofolhas de grafeno quimicamente modificadas: preparação, estudo da estrutura e propriedades físico-químicas

Abstract

In this study, the influence of the tetraethylenepentamine (TEPA), covalently bound to the walls of graphene oxide (GO), on the thermal and mechanical properties of nanocomposites based on diglycidyl ether of bisphenol A (DGEBA)/graphene was investigated. The GO-TEPA nanosheets were synthesized in a fast reaction assisted by microwave radiation. The mixture of nanofiller with epoxy resin was carried out by roller mill in order to reach homogeneous dispersions. The morphology and properties of nanosheets of GO and GO-TEPA were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetry (TG/DTG) and Raman spectroscopy. Composites containing 0.1, 0.3 and 0.5 wt% of GO and GO-TEPA were prepared and improvements in the thermal and mechanical behavior of theses materials were observed. The composites were characterized by SEM, differential scanning calorimetry (DSC), nanoindentation, dynamic mechanical thermal analysis (DMA) and by the flash laser method. Nanoindentation measurements showed significant increases of up to 73% on Young's modulus and 140% on hardness for the composite containing 0.5 wt% GO-TEPA. The thermal conductivity measurements showed gains of up to 103% for composites compared to pure polymer. The thermal and mechanical performance of composites was corroborated by DMA and DSC measurements that showed increases of up to 20°C in the glass transition temperature (Tg). The good thermomechanical behavior of the composites strongly dependes on the degree of exfoliation and dispersability of nanofillers in the polymer matrix, which are associated with the extent of chemical modification of graphene nanosheets.