Elastic CNT–polyurethane nanocomposite: synthesis, performance and assessment of fragments released during use

Abstract

Intended for use in high performance applications where electrical conductivity is required, we developed a CNT-TPU composite. Such a composite can be prepared by melt processing (extrusion) on an industrial scale. Due to the known hazard upon inhalation of CNTs, we assessed three degradation scenarios that may lead to the release of CNTs from the composite: normal use, machining and outdoor weathering. Unexpectedly, we find that the relative softness of the material actually enhances the embedding of CNTs also in its degradation fragments. A release of free CNTs was not detected under any condition using several detection methods. However, since machining may induce a high acute dose of human exposure, we assessed the cytotoxicity potential of released fragments in the in vitro model of precision-cut lung slices, and found no additional toxicity due to the presence of CNTs. At very low rates over years, weathering degrades the polymer matrix as expected for polyurethanes, thus exposing a network of entangled CNTs. In a preliminary risk assessment, we conclude that this material is safe for humans in professional and consumer use.

Releases from transparent blue automobile coatings containing nanoscale copper phthalocyanine and their effects on J774 A1 macrophages

“…Our results are consistent with other studies which investigated in vitro or in vivo toxicity of sanding dust from paint containing nanoparticles (NanoTiO 2 and nano silica) (Wohlleben et al, 2011;Saber et al, 2012a, b;Kaiser et al, 2013) or from CNTs containing polymer composites Wohlleben et al, 2013;Ging et al, 2014;Schlagenhauf et al, 2015;Saber et al, 2016;Civardi et al, 2016). For example, Ging et al (2014) demonstrated that the survival of Drosophila was reduced at each dose tested with free amine functionalized CNTs, while there was no toxicity when these CNTs were embedded in epoxy.…”

“…Additionally, the abrasion process may also directly impact on the concentration and size of released particles. For instance, Wohlleben et al (2011Wohlleben et al ( , 2013 showed that simulated long term wear using a Taber abraser resulted in fewer released particles from carbon nanotube (CNTs)-based composites than more aggressive sanding processes applied to identical materials. Furthermore, a combined mechanical and chemical stresses applied to simple and multi- …”

“…6 (Wohlleben, 2012;Wohlleben et al, 2011Wohlleben et al, , 2013Walter et al, 2014). The size distribution analyses of pristine n-CuPc and Frag n-CuPc in RPMI showed that the dispersion of pristine n-CuPc contained smaller particles than the Frag n-CuPc.…”

“…For example, Ging et al (2014) demonstrated that the survival of Drosophila was reduced at each dose tested with free amine functionalized CNTs, while there was no toxicity when these CNTs were embedded in epoxy. Wohlleben et al (2013) showed that there were no cytotoxic effects of Thermoplastic polyurethane (TPU) with or without CNTs on lung tissue in vitro. Saber et al (2012aSaber et al ( , b), 2016 found that there were no additive effects of adding CNTs to epoxies or adding NanoTiO 2 to paint for any of the pulmonary endpoints in mice (pulmonary inflammation and DNA damage and hepatic histopathology).…”

Quantitative measurement of carbon nanotubes released from their composites by thermal carbon analysis

“…However, the release of free CNTs and CNTs partly embedded in matrix debris into the air may occur during mechanical and abrasion processes involving CNT composites. Some studies have indicated that CNT-matrix mixtures are less harmful than free CNTs [1][2][3][4]. However, the harmful effects of CNT-matrix mixtures have not yet been fully evaluated.…”