title: 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.
authors.affiliation: BASF SE, Material Physics, GMC, 67056 Ludwigshafen, Germany. wendel.wohlleben@basf.com
authors.forename: Wendel
authors.initials: W
authors.lastname: Wohlleben
authors.forename: Matthias W
authors.initials: MW
authors.lastname: Meier
authors.forename: Sandra
authors.initials: S
authors.lastname: Vogel
authors.forename: Robert
authors.initials: R
authors.lastname: Landsiedel
authors.forename: Gerhard
authors.initials: G
authors.lastname: Cox
authors.forename: Sabine
authors.initials: S
authors.lastname: Hirth
authors.forename: Željko
authors.initials: Ž
authors.lastname: Tomović
mesh_terms: D000818:Animals; D003460:Crystallization / Q000379:methods; D055119:Elastic Modulus; D004553:Electric Conductivity; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects* / Q000473:pathology*; D008422:Materials Testing; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000633:toxicity*; D010316:Particle Size; D051381:Rats; D017208:Rats, Wistar
chemical_list: D037742:Nanotubes, Carbon