Reinforcement of graphene nanoplatelets on water uptake and thermomechanical behaviour of epoxy adhesive subjected to water ageing conditions

Abstract

Adhesive joints are frequently utilized due to their lightweight nature and minimal damage to the substrates. However, their application is constrained by a lack of reliable performance under moist conditions. This study assesses the impact of incorporating varying concentrations (0.25–0.75 wt%) of graphene nanoplatelets (GNPs) on moisture uptake, dynamic thermal properties, and tensile behaviour of engineered epoxy adhesives when subjected to water for periods of up to 8 weeks. The objective of this study is to ascertain the optimal concentration from the standpoint of degradation in the thermomechanical performance of the epoxy resulting from water ageing. The addition of GNP results in a 45% reduction in the diffusion coefficient of the 0.25 wt% GNP-modified epoxy relative to the unmodified epoxy. The reduced absorption of water by the GNP-reinforced adhesive results in diminished thermomechanical degradation, particularly during the initial immersion period (less than 14 days). The loss modulus exhibits an increase of up to 21% in comparison with the unmodified epoxy. The reduction in tensile strength of the modified epoxy is 53% less than that of the unmodified epoxy following 14 days of water ageing. Under the same water ageing conditions for 14 days, the epoxy modified with 0.25 wt% GNP exhibited a 75% increase in tensile strength compared to the unmodified epoxy. This work may facilitate the GNP application in epoxy adhesive joints, thereby enhancing their durability under high humidity conditions.