Seven cellulose nanocrystalline (CNC) powder samples from North American facilities were fully characterized and tested for dustiness and the potential to release nanoparticles upon mixing. In water all of the CNC samples were readily re-dispersible and had similar nanoscale lengths and widths. With respect to the standard dustiness test, some of the CNC powders were highly dusty whereas others exhibited very low potential for dust formation. While the CNC powders were all composed of micron sized particles, closer examination did reveal the presence of nanoparticles in the size range of 500 nm, which appeared to be adsorbed or attached onto the larger particles. Free nanoparticles were not observed in any of the powder samples. Analysis of the air in an exposure chamber using an SMPS sampler, during controlled mixing of the powdered CNC, demonstrated the presence of numerous nanoparticles in two distinct fractions representing nanoparticles from 50-200 nm and 400-800 nm. Samples of the nanoparticles in the chamber were sampled onto grids using a thermophoretic sampler (TPS) and characterized by electron microscopy. For each powder, regardless of the drying technology employed, the nanoparticles captured all appeared similar and were greater than 500 nm in length. In contrast to the SMPS readings, no nanoparticles in the range of 50-200 nm were observed on these sampling grids. It is possible that these nanoparticle size fractions are short lived in the exposure chamber and quickly agglomerate onto the larger nanoparticles that are present. It is thought that the particles in the range of 400-800 nm were either being released from the larger particles, due to the energy imparted, or generated from the powders as a result of the increased mixing energy. Overall, the data indicates that during the manipulation of CNC powders, workers could be exposed to nanoparticles that are markedly larger and different from the form of CNC nanocrystals in aqueous solutions.<br/>

Occupational health and safety characterization and assessment of CNC’s from North American producers

253rd National Meeting (2017)

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