E. Sahle-Demessie, C. Han, A. Zhao, N. Gagliardi
U.S. Environmental Protection Agency,
Keywords: polymer nanocomposite, aging, nanorelase, functionalized-CNT-EPOXY
Summary:Epoxies are widely used in various applications, including coatings, electronics insulations, and waterproofing applications due to their excellent properties such as good adhesion, electrical insulation, and heat resistance along with the strong mechanical property. Currently, nanomaterials, such as carbon nanotubes (CNTs), carbon nanofibers, graphene, graphene oxide and nano-carbon black, are extensively utilized to improve their physicochemical properties since the improvement of their properties using micromaterials reached the apex. 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.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. In addition to the investigation of property changes of epoxy-CNT composites by different functional groups on CNTs, the release of nanomaterials from the composites into the environment has become a significant issue because an ample amount of nanomaterials is used to improve the polymers’ properties, and many studies reported that some nanomaterials demonstrated toxicity to humans and animals. Therefore, it is important to study the release of nanomaterials from polymer composites into the environment. In the present study, we prepared different epoxy-multiwalled-CNTs (MWCNTs) composites using 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 aged samples by accelerated weathering were 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.