Bisphenol-A-Carbon Nanotube Nanocomposite: Interfacial DFT Prediction and Experimental Strength Testing

Epoxies, their derivatives, and composites, due to superior specific strength, are preferred for many potential applications in the field of automobiles, aircraft, bonding of structures, protective coatings, water filtration, etc. As structural members in automobiles and aircraft, the epoxy-based components are exposed to various static/dynamic mechanical loading conditions during their service life. The interfacial interactions, between the matrix and reinforcement, greatly affect the final properties of the composites. The present study demonstrates that the solvent used for the preparation of the composite can also contribute toward interfacial interactions. Present research systematically finds out a suitable solvent (acetone) and reinforcement type [multi-walled carbon nanotube (CNT)] for epoxy [bisphenol-A (BPA)] nanocomposites. Dynamic and static strengths of the as-prepared epoxy-CNT nanocomposites were carefully investigated. Well dispersed CNTs in acetone were mixed with an ester of BPA under constant magnetic stirring conditions. Samples of tablet shape were prepared for testing static and dynamic performance of the composite using a nano-indentation technique. Considerable enhancement by 55 and 22% in the static elastic modulus and hardness of BPA-CNT composites, respectively, was observed (compared with that of pristine BPA). The storage modulus and tan-delta of the nanocomposites were also improved by 14 and 46%, respectively. Improved static and dynamic performance, reported in this work, significantly enhances the scope of utilization of BPA-CNT-based nanocomposites under severe static and dynamic loading conditions simultaneously. Static and dynamical analysis of CNT-reinforced epoxy provides more realistic understanding of the mechanical performance of the nanocomposite. Density functional theory (using QuantumATK software) simulations were performed to investigate and identify the alterations in the atomic morphology of CNTs during interfacial interaction with the acetone molecule and epoxy matrix. The calculations predicted that CNTs with mild defects as compared to pristine CNTs were better suited for synthesis of the nanocomposite and also assisted in a homogeneous distribution of CNTs in BPA without aggregation (with acetone as the solvent). Furthermore, structural changes in CNTs after treatment with BPA and the curing agent and the role of defects are studied in detail.