Determination of Coating Thickness of DEHS on Submicron Particles by Means of Low Pressure Impaction

The increasing use of submicron and nano‐scaled particles in process engineering sets a demand for new methods for the characterization of particle properties. In the present work low pressure impaction as a very sensitive method for the characterization of the coating of nanoparticles is introduced. The determination of the coating thickness is based on the change of effective density due to the differing densities of particle and coating material. As model systems the coating of spherical silver nanoparticles and agglomerates of silver nanoparticles with DEHS (di(2‐ethylhexyl)sebacate) were used. A tandem differential modelling analyzer (DMA) setup served as a reference for the measurement results obtained with the low pressure impactor (LPI). The LPI showed a very high sensitivity for the coating of spherical particles. Changes of the particle radius below 1 nm could be detected. In contrast to spherical particles, agglomerated particles did not show a clear correlation between coating thickness and the change of effective density for coated agglomerates.