Abstract
Nanocomposites modified with graphene nanoplatelet (GNP) have garnered significant attention and widespread application across various domains due to their substantial property enhancements. Nevertheless, excessive GNP incorporation not only leads to agglomeration within the polymer matrix but also degrades the base polymer's performance. Consequently, an investigation into the impact of GNP content on nanocomposite performance holds considerable significance. This study involves the dispersion of GNP with varying weight percentages into epoxy resin (EP) via ultrasonic dispersion to synthesize nanocomposites. The isothermal viscose-time properties were investigated to clarify the effect of the GNP on the curing speed and to suggest a suitable operating time for industrial production. Differential scanning calorimetry (DSC) was employed to investigate the curing kinetics so as to calculate the kinetic parameters and guide the curing process in practical industrial applications. In addition, mechanical properties and microstructure morphologies were analyzed by the direct tensile tests and scanning electron microscope (SEM) tests. Results showed that the addition of GNP in appropriate amounts is effective in promoting the curing reaction and improving the mechanical behavior. Specifically, GNP content was positively correlated with the increase of viscosity during the curing of the system. The EP@GNP-2 blend with 2 wt% GNP had the most significant effect on reducing the apparent activation energy, indicating that too much GNP may have an inhibitory effect on the curing reaction. The curing process parameters, including the gelling temperature (Tgel), curing temperature (Tcure) and post-treatment temperature (Ttreat) were calculated through the T-β extrapolation method. The elastic modulus of EP@GNP-1, EP@GNP-2 and EP@GNP-3 specimens increased by about 5%, 18% and 25%, respectively. However, the elongation at break showed a trend of increasing and then decreasing with the increase of GNP content. SEM tests show that excessive GNP content will attribute to the formation of a long barrier-like structure in the epoxy matrix to block the cross-linking of epoxy molecules on both sides, and the GNP agglomerates become stress concentration points and aggravate the brittleness of the nanocomposite. Furthermore, although a clear negative correlation between GNP content and thermal stability was revealed, the incorporation of GNP significantly enhances electrical conductivity. The results suggest that a reasonable GNP content is necessary, and a GNP content of 2 wt% is a recommended value for improving mechanics and curing efficiency.
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