USE OF DIFFERENT GRAPHENE-DERIVATIVES TO PREPARE HIGH-PERFORMANCE POLYMERIC COMPOSITES

Abstract

The outstanding properties of graphene-based nanomaterials have been found very useful for improving the mechanical, electrical, barrier and optical properties of graphene/polymer composites. Some precise investigations have shown that the suitability of different derivatives of graphene, such as, graphene oxide (GO) and reduced graphene oxide (rGO), as fillers in polymer matrix composites, is highly dependent on targeted applications. Therefore, it is desirable to investigate the comparative performance of these graphene-derivatives (G-derivatives) for a particular set of properties. In this dissertation work, we have exposed the effectiveness of some common G-derivatives as fillers in graphene-based nanofillers reinforced acrylonitrile butadiene styrene (ABS) composites. For this purpose, initially, efforts have been made to reduce the processing time for synthesis of high-quality GO. This has been achieved through the addition of nitric acid (HNO3) in the previously used combination of sulphuric-phosphoric acids (H2SO4-H3PO4). The introduction of HNO3 has been intentionally done to accelerate the intercalating potential of the mixture of H2SO4 and H3PO4. Comparative properties of GO prepared via three different approaches have been discussed in the related sections with the help of X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy and Thermo-gravimetric analysis (TGA). Subsequently, the graphene oxide synthesized via HNO3-based approach has been reduced through two different reduction processes (i.e. chemical reduction using hydrazine hydrate and thermal annealing) and three different types of composites were prepared through melt blending of these nanofillers individually in ABS. The basic properties of rGO synthesized via two different reduction techniques have been analyzed using XRD analysis, FESEM images, EDX analysis, Raman spectroscopy and XPS analysis, and then the effect of these nanofillers on tensile and viscoelastic properties of ABS matrix composites have been discussed in the related sections with the help of XRD analysis, FESEM images, EDX analysis, Tensile testing and Dynamic mechanical thermal analysis (DMA). Further, corresponding properties of most suitable G-derivative reinforced ABS composites, prepared by varying the content of filler from 0.5 – 6 wt%, have been discussed to suggest the optimum content of filler v | P a g e for superior tensile and viscoelastic properties of such graphene/ABS composites. Finally, in order to improve one of the defects generated due to the use of harsh processing conditions employed during the preparation of GO and rGO, the doping of two specific metallic species; i.e. Boron (a metalloid) and Nickel (a transition metal) in rGO nanosheets has been experimentally performed to expose the effectiveness of metallic dopants on corresponding properties of selective G-derivative reinforced ABS matrix composites. Furthermore, some typical secondary correlations based on dynamic storage modulus (i.e. variation in stiffness, degree of entanglement and C-factor) and Cole-Cole plots have been used to validate the change in basic viscoelastic properties and to verify the compatibility of particular graphene-based nanosheets as reinforcing filler in ABS matrix. In addition, the creep and recovery profiles of different graphene-based nanomaterials reinforced ABS composites have been studied to investigate the comparative mechanical stability of different composites.