Aging and release of pristine and functionalized carbon nanotubes from epoxy-nanocomposites during accelerated weathering

Epoxy-based materials are widely used for coatings, electronics insulations, and waterproofing applications due to their excellent properties such as excellent adhesion, electrical insulation, and heat resistance along with the strong mechanical property. The making of composites by mixing nanomaterials, such as carbon nanotubes (CNTs), carbon nanofibers, graphene, graphene oxide and nano-carbon black with epoxy are extensively utilized to improve their physicochemical properties. CNTs as a nano-filler in epoxy-nanomaterial composites are widely used in the improvement of their properties because they are very light, thermally stable and mechanical strength. Composites are made by filling epoxy resins through catalytic homopolymerisation, or with a wide range of co-reactants. Moreover, CNTs may have different functional groups, including -NH₂, -COOH, and -OH, depending on functionalization methods. Since epoxy resins are reactive polymers, various functional groups on CNTs may react with epoxy resins and change the nanocomposite properties during curing processes. Usually, curing agents are added in epoxy-nanomaterial resins for crosslinking, and the curing is done at high temperatures. Therefore, it is of great interest to investigate the effect of the CNT fillers with different functional groups on the property changes of epoxy-CNT composites for long-term applications. The problem of environmental aging on the change in mechanical properties, leaching of phenolic compounds and release of filler nanoparticles. Different epoxy-multiwalled-CNTs (MWCNTs) composites were prepared by filling a polymer with pure MWCNTs, NH₂-, and COOH-functionalized MWCNTs to study the effect of functional groups on the properties of epoxy-MWCNT nanocomposites. We also aged the nanocomposites in an accelerated weathering chamber, which simulates actual weather conditions in summer and rainy conditions. Moreover, we collected water samples, which were used to simulate raining conditions, during the weathering process. The accelerate aging of epoxy was characterized with TGA, DSC, SEM, FTIR and an optical microscopy technique. The collected water samples were analyzed with LC/MS and dynamic light scattering. The release of CNTs from the aged composite was characterized by TEM, dynamic light scattering, and single particle-ICP-MS. The results of the interaction of different functional groups on MWCNTs with epoxy, the characterization of the aged composites, the release of MWCNTs, microplastics, and organic compounds from the aged nanocomposites will be discussed in detail at this presentation. The study could provide how molecular-level interactions between the functionalized CNTs and Epoxy polymers affect the aging and release of CNTs.