Network Aggregation of CNTs at the Surface of Epoxy/MWCNT Composite Exposed to UV Radiation | NIST

Abstract

Carbon nanotubes (CNTs) are increasingly incorporated in polymers to enhance their mechanical and electrical properties. However, organic polymers are prone to degrade when exposed to UV radiation. Therefore, CNTs in a polymer nanocomposite could eventually be released into the environment during their life cycle, which might have a negative impact on the environment and thus presents a roadblock to their use. This study investigates the degradation of an amine-cured epoxy/multi-walled CNT (MWCNTs) composite and characterizes the CNT concentration at the nanocomposite surfaces during exposure to UV radiation. An amine-cured diglycidyl ether of bisphenol A epoxy and MWCNTs pre-dispersed in the epoxy resin were used as the polymer matrix and CNT, respectively. Epoxy/MWCNT composites having a thickness of approximately 125 μm were exposed to 75 % RH, 50 o C, and UV radiation between 290 nm and 400 nm in a NIST-developed UV chamber. Chemical degradation, mass loss, and surface morphology were measured at specified exposure time using FTIR, gravimetry, SEM, and AFM techniques. Results show that the epoxy matrix in the nanocomposite containing 0.72 % (by mass) MWCNTs undergoes rapid photodegradation, resulting in a large concentration increase and network aggregation of MWCNT at the nanocomposite surface with exposure time.