Nanoparticles aerosols generation from materials under stress : Characterization and Measurement
Résumé
The overwhelming use of nanoparticles in contemporary applications, as a result of possible opportunities for innovation, has brought huge potential risks to the workers and consumers due to their release/emission during their use. Therefore, it is necessary to study such an emission under different conditions of use so that the products are safe by design. The present study is focused on this aspect. Based on a multiaxial research approach, it has been found that the release of the aerosol particles, in general, is a direct result of the wear or fretting of surfaces due to various extrinsic and intrinsic surface properties which get affected during stress application conditions. In order to mimic these stress conditions, a linear abrasimeter (Taber 5750) is selected along with real time aerosol measuring devices (CPC, APS and SMPS), and a system for collecting the sampled particles for their further microscopic analysis. A range of materials treated with nanoparticles of titanium dioxide and silica, including both surface (nano-coatings) as well as bulk (nanoparticles reinforcement) treated, are tested in order to measure their particles emission tendency. The parameters studied include external load acting on the abrasion system, relative sliding speed, number of abrasion cycles and type of abrasives. The imperativeness of a proper nanosecurity during the tests is ensured by the conformity of a nanosecured post with an enclosing emission test chamber. The measurement of particles emission during the variation in abrasion parameters and the proper nanosecurity measures have allowed us to design and develop a versatile system which could quantify (semi-quantify to precise) as well as characterize the particle emission under diverse stress conditions. This study further benefits from a state of the art theoretical approach (under development) which emphasizes on the development of a scientific base explaining and justifying the reason behind the particles emission. The results show that during abrasion, considerable emission of wear particles occurs in the form of polydispersed aerosol. The particles are principally in micronic size range with a nanometric fraction, thus having a composition which is representative of the original matrix. The existence of nanoparticles in free state (not embedded inside a matrix) is also found to be likely in the cases of polymers, however, emitted particles number concentration in such a case is limited.