Effects of the shear rate on dispersion characteristics of industrial-based functionalized/non functionalized graphene in an epoxy matrix†

Abstract

Epoxy resin, widely recognized for its durability and chemical resistance, exhibits superior performance when reinforced with nanofillers, making it ideal for demanding engineering applications. This research aims to explore the state-of-the-art developments in epoxy resin and graphene composites via two industrially feasible approaches, such as mechanical stirring (MS) and a high-speed shearing process (HSS), providing insights into the mechanisms of reinforcement and the resulting improvements in material characteristics. As nano-additives, two varieties of graphene powders—functionalized (Gp-C) and non-functionalized (Gp-A)—are chosen. On fractured surfaces, XRD measurements and electron microscopy (both FESEM and HRTEM) are used to verify the filler dispersion and the creation of a strong interface within the epoxy matrix. The remaining functional groups in Gp-C have the ability to react with anhydride or epoxy groups to produce covalent bonds that improve the mechanical and thermal properties of the composite by improving interfacial adhesion. On the other hand, Gp-A graphene reduces the composite's overall mechanical properties by producing an uneven dispersion and possible weak spots. We expanded the research by utilizing Gp-A and Gp-C graphenes (tensile strength of 380 ± 20 MPa, around 10% and 420 ± 20 MPa, about 22% improvements) as fillers in glass fiber single-layer epoxy laminates, building on the incorporation of graphene fillers in epoxy resin. The goal was to examine not only the mechanical enhancements but also the antibacterial properties (zone of inhibition (ZOI) values of 1.2 mm² for E. coli and 1.8 mm² for S. aureus in the GNF (Gp-A) laminate and 0.8 mm² for both bacteria in the GF (Gp-C) laminate). The antibacterial efficacy of graphene-coated epoxy laminates was evaluated using CFU (colony-forming unit) testing, where GNF achieved a log reduction of ≥1.61 for E. coli and 0.49 for S. aureus, while GF demonstrated enhanced antibacterial activity with log reductions of 1.13 for E. coli and 3.38 for S. aureus, attributed to ROS-mediated oxidative stress and bacterial membrane disruption. This study addresses the challenges in dispersing nano-additives in epoxy resin and highlights innovative industrial development prospects, offering valuable insights for enhancing performance in demanding engineering sectors, including infrastructure, marine, and chemical processing industries.