Carbonaceous nanomaterials are a group of innovative materials that include multi-walled carbon nanotubes (CNTs). They are playing an increasingly important role in many areas of industry due to their outstanding electrical and mechanical properties. By designing these new materials to be safe for use, unacceptable risks to humans should be largely excluded from the outset. This project investigated causes for the very different dustiness behaviour of various CNTs in order to derive recommendations for safe application.
Different methods for the activity-related investigation of dustiness behaviour were used to examine different CNTs for their dustiness. The comparability of the different methods was demonstrated, which is an important building block for the evaluation of materials with regard to their dustiness. These results were compared with a selection of morphological properties (e.g. length, diameter and curvature). The materials with the highest dustiness are all in a diameter range between 20 and 50 nm and in the lower middle range in terms of their curvature. This is an interesting indication, as in this diameter range a transition between a critical and a less critical rigidity (fibre stiffness) in terms of damaging effect is expected. Initial findings from the analysis of fibre curvature point to a further connection between dusting tendency, morphology and rigidity of a material. This is being further investigated in research project F 2365.
The project results are particularly relevant for the development of application-safe carbonaceous nanomaterials. Thereby the non-biodegradable CNTs with a low dustiness, non-critical rigidity and non-critical fibre morphology pose a lower health risk than non-biodegradable CNTs with a high dustiness and a release of rigid, critical fibre morphologies.
Unit 4.5 "Particulate Hazardous Substances, Advanced Materials"