The addition of graphene as an efficient nano-filler to different polymer matrices lead to a substantial improvement in different physical properties which, as a result, pave the way towards promising applications. In this work, Polystyrene (PS) was reinforced with different low loadings of graphene oxide (GO). The latter was prepared according to the Hummers method. The incorporated weight fractions were (0.01, 0.05, 0.1, 0.25, 1.0) wt. %. Solution blending was the adopted approach to prepare the nanocomposites. The resulted nanocomposites were characterised compared to the neat polymer. Many tools were employed to investigate the structure, morphology, thermal, and thermo-mechanical behaviour of GO, neat polymer, and the nanocomposites. The structural and morphological outcome for GO and PS was confirmed compared to the literature. The outcome confirmed as well the good dispersion of GO nano-sheets in the PS. The thermal and thermo-mechanical properties were enhanced for the nanocomposites compared to the neat polymer. The results emphasised the improvement of nanocomposites' performance as the inclusion of GO went higher.
Carbon based nano-fillers for a range of applications have recently attracted a considerable attention due to their exceptional mechanical and physical properties such as high strength, high stiffness and high thermal and electrical conductivities. Many of research groups have prepared and study the features of these materials according to their low cost, low weight and ease of processing. Graphite, fullerene, carbon nano-tubes and the recently discovered material, graphene, are derived from this fascinating material, carbon, and they are the most widely studied allotropes of interest to technologists and researchers due to their unique applications in various fields.
Graphene is a planar honeycomb lattice that is a two dimensional, one atom thick carbon sheet. Its properties include high thermal conductivity, high intrinsic electron mobility, optical transmittance of 98%, large specific surface area and high Young’s modulus. These properties offer graphene the potential for numerous different applications in many disciplines such as sensors, energy conversion, storage devices, solar cells and reinforced composites. To enable the exploitation of these unique properties in applications, graphene and its derivatives have been successfully prepared using different routes such as bottom-up chemical vapour deposition and top down exfoliation of graphite by means of oxidation, intercalation and/or sonication. As a consequence of their high G-G interactions (kind of non-covalent interaction between electron rich G system and another molecule), graphene sheets are not directly mixed with the polymer matrices to produce polymer nanocomposites as the graphene sheets tend to stack into large aggregates. For this reason, graphene oxide is usually incorporated into polymer matrices for making high quality polymer nanocomposites, as it has better compatibility with polymers, forms a uniform dispersion and offers a possibility of mass production.
In this study, different low loadings of GO were incorporated homogenously into a PS matrix and different structural, thermal properties were studied as well as the nanomechanical behaviour for the polymer, and the nanosheets imaged in the cryogenically fractured surface. The incorporation of low loadings of the GO led to improvement in thermal and thermomechanical performance as the results of TGA, DSC and DMA indicated. As the homogenous dispersion for the nanosheets in the polymer matrix is a prerequisite for a good performance, this kind of dispersion was verified via different microscopic techniques carried out in this study. These techniques included OM, SEM and TEM. According to the very low weight fractions used in this study, no sharp peaks of GO appeared in Raman spectroscopy for the nanocomposites. Weak shoulders appeared in FTIR diagram and tiny humps can be seen in the curves of XRD. These can be attributed to the low loadings of GO in the PS that led to dilution of GO in the polymer matrix. In general, the incorporation of GO in PS using low loadings led to improve thermal and thermomechanical performance for the nanocomposites compared to the neat polymer. Td, Tg, and storage modulus were increased as the weight fraction of GO went higher.