Impact of UV irradiation on multiwall carbon nanotubes in nanocomposites: Formation of entangled surface layer and mechanisms of release resistance

Abstract

Multiwall carbon nanotubes (MWCNTs) are nanofillers used in consumer and structural polymeric products to enhance a variety of properties. Under weathering, the polymer matrix will degrade and the nanofillers may be released from the products potentially impacting ecological or human health. In this study, we investigated the degradation of a 0.72 % (by mass) MWCNT/amine-cured epoxy nanocomposite irradiated with high intensity ultraviolet (UV) light at various doses, the effects of UV exposure on the surface accumulation and potential release of MWCNTs, and possible mechanisms for the release resistance of the MWCNT surface layer formed on nanocomposites by UV irradiation. Irradiated samples were characterized for chemical degradation, mass loss, surface morphological changes, and MWCNT release using a variety of analytical techniques. Under 295 nm to 400 nm UV radiation up to a dose of 4865 MJ/m2, the nanocomposite matrix underwent photodegradation, resulting in formation of a dense, entangled MWCNT network structure on the surface. However, no MWCNT release was detected, even at very high UV doses, suggesting that the MWCNT surface layer formed from UV irradiation of polymer nanocomposites resist release. Four possible release resistance mechanisms of the UV-induced MWCNT surface layer are presented and discussed.

High‐Performance UV Protective Waterborne Polymer Coatings Based on Hybrid Graphene/Carbon Nanotube Radicals Scavenging Filler

“…Numerous theoretical and experimental studies have demonstrated this capability for carbon nanotubes (CNTs) and similar results have been reported for graphene (G), too . Therefore, both CNTs and graphene have been added in small amount to polymer matrix in order to convey the radical scavenging functionalities to the composite film. In most of the cases, when polymer composites containing a few CNT percentage (0.2–5 wt%) are exposed to strong UV irradiation, at higher temperature (50–60 °C) in oxygen atmosphere, the presence of the filler delay the photooxidation process.…”

A material experiment for small satellites to characterise the behaviour of carbon nanotubes in space – development and ground validation

“…The resistance ratio of the composite material (ME) decreases under UV light. Photo-induced depolymerisation and erosion processes results in a lower resistance connection between the CNTs and changes the electrical properties of the composite sample [26,27]. These interactions between the matrix material and the carbon nanotubes are known and is part of new sensor concepts [26,28].…”

Nano-Charged Polypropylene Application: Realistic Perspectives for Enhancing Durability

“…less than 200 h, the rates of carbonyl formation were found very similar to that observed for unfilled polyethylene film but at longer irradiation times the carbonyl formation was found to increase for lower MW-CNTs contents (0.1 wt %, 0.2 wt % and 0.5 wt %), and to decrease for higher MW-CNTs contents (1 wt % and 2 wt %) [ 33 ]. The stabilization effect of MWCNTs was also found for other polymers: epoxy [ 34 , 35 , 36 , 37 ], Thermoplastic Polyurethane (TPU) [ 38 ], Polyamide 6,6 (PA6) [ 39 , 40 , 41 ], PLA [ 42 ] and isotactic polypropylene (iPP) [ 40 , 43 ]. Epoxy containing MWCNTs exposed to UV radiation degraded at a much slower rate than the unfilled epoxy or the epoxy/nanosilica composite [ 37 ].…”