Microwave exfoliated reduced graphene oxide epoxy nanocomposites for high performance applications

Abstract

a b s t r a c tGraphene has captured the attention of scientific community due to recently emerging high performance applications. Hence, studying its reinforcing effects on epoxy resin is a significant step. In this study, microwave exfoliated reduced graphene oxide (MERGO) was prepared from natural graphite for subsequent fabrication of epoxy nanocomposites using triethylenetetramine (TETA) as a curing agent via insitu polymerization. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), C 13 NMR spectroscopy, X-ray photoelectron spectroscopy (XPS) and ultravioletevisible (UVevis) spectroscopy were employed to confirm the simultaneous reduction and exfoliation of graphene oxide. The reinforcing effect of MERGO on epoxy resin was explored by investigating its static mechanical properties and dynamic mechanical analysis (DMA) at MERGO loadings of 0 to 0.5 phr. The micro-structure of epoxy/MERGO nanocomposites was investigated using scanning electron microscope (SEM), transmission electron microscope (TEM) and XRD techniques. The present work reports an enhancement of 32%, 103% and 85% in tensile, impact and flexural strength respectively of epoxy by the addition of even 0.25 phr MERGO. At this loading elastic and flexural moduli also increased by 10% and 65%, respectively. Single-edge-notch three-point-Bending (SEN-TPB) fracture toughness (K IC ) measurements were carried out where a 63% increase was observed by the introduction of 0.25 phr MERGO. The interfacial interactions brought about by graphene also benefited the dynamic mechanical properties to a large extent in the form of a significant enhancement in storage modulus and slightly improved glass transition temperature. Considerable improvements were also detected in dielectric properties. The epoxy nanocomposite also attained an ac conductivity of 10 À5 S/m and a remarkable increase in dielectric constant. The simple and cost effective way of graphene synthesis for the fabrication of epoxy/MERGO nanocomposites may be extended to the preparation of other MERGO based polymer nanocomposites. This remarkable class of materials has thrown open enormous opportunities for developing conductive adhesives and in microelectronics.

High performance graphene oxide/epoxy nanocomposites fabricated through the solvent exchange method

“…Moreover, the observed decrease in the height of tan δ by increasing GO content (Fig. ) confirms the restricting effect of GO particles on the chain mobility of the epoxy matrix, which is indicative of strong interfacial interactions between GO sheets and the epoxy matrix .…”

“…This significant enhancement in elongation at break is attributed to the uniform dispersion of GO, strong interfacial interaction between GO and epoxy and reduction of epoxy crosslink density. However, at higher GO loading, the strong interactions between the GO sheet and epoxy matrix leads to diminishing epoxy molecular mobility and slightly reduces the elongation at break .…”

An alternative synthesis route to graphene oxide: influence of surface chemistry on charge transport in epoxy-based composites

“…Indeed, our directly synthesized mGO (i.e. without being subjected to any subsequent reduction process) displays a smaller related mass loss than either chemically reduced GO (via reaction with hydrazine hydrate) [53] or microwave reduced GO [32]. Figure 4 shows XPS data obtained from the precursor graphite, the GO and the mGO powders.…”

“…The associated reactions between GO and epoxy were investigated and presented elsewhere [29]. Therefore, GO produced in this way is either used sparingly to modify mechanical performance [30] or further processed by reduction [31,32] or functionalization [33][34][35]. In some cases, even the functionalization of GO was not sufficient to prevent alteration of the epoxy stoichiometry [36,37].…”

Reasons and remedies for the agglomeration of multilayered graphene and carbon nanotubes in polymers

“…The second highest improvement in K 1C is achieved with a combination of sonication and magnetic stirring and K 1C increased by 109% [61]. The smallest improvements of K 1C are achieved when sonication is coupled with ball milling [12,62–63]. Both sonication and ball milling reduce the sheet size and produce surface defects [64–78], and we believe that this impedes the improvement of K 1C .…”