Characterization of emissions arising during machining of nanocomposites

Status:

completed 04/2013

Aims:

Nanomaterials and their application are regarded as one of the most significant technologies of the 21st century. Nanomaterials are increasingly being incorporated into familiar materials (polymers, metals) in order to lend new properties to them. Over the life cycles of these new nanocomposites, it is probable that in certain cases they will be machined, for example by drilling or grinding. The objective of the project is to characterize the emissions, particularly of nanoparticles, arising during the machining of nanocomposites.

Activities/Methods:

At the Chair of Particle Process Engineering of the University of Kaiserslautern, nanocomposites are studied that are either sourced in ready-to-use form (such as Zentallium, an aluminium-CNT composite) or produced in the Chair's own laboratories (epoxy resin with CNTs). On test apparatus specially erected for the studies, the nanocomposites are machined and the emissions occurring in the process are analysed. Collecting processes for imaging methods (electron microscopy) and direct-indicating instruments for counting (the scanning mobility particle sizer, SMPS; the electrical low-pressure impactor, ELPI) are used for this purpose.

Results:

The greatest number of particles released in the sub-micrometre range were observed by the University of Kaiserslautern in grinding tests on CNT-epoxy resin composite materials. Some of the particles which were released and were collected by means of ELPI or electrostatic filters are seen under the scanning electron microscope to have exposed fibre ends. Isolated free CNTs were not detected. We are not aware at this time of any toxicological assessment that has been performed of such composite particles.

Based upon this experience, the IFA drew up a proposal for an evaluation by scanning electron microscope of collected nanoscale particles. Specifically, the number of CNTs was to be determined by means of proposed counting criteria.

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