10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Aerosol Release during Mechanical Solicitation of Tio2 Nano-Additived Paint
CHARLES MOTZKUS, François Gaie-Levrel, Nicolas Feltin, Stephane Delaby, Scientific and Technical Center for Building (CSTB)
Abstract Number: 921 Working Group: Indoor Aerosols
Abstract The market of the nanocomposite materials in the construction industry is exponentially growing. Several types of nano-objects are currently used, in particular titanium dioxide (nano-TiO2). However, many questions are still open concerning the impact of these nanomaterials on the human health and the environment as previous studies showed. The degradations induced by the aging mechanisms could leads to the release of particles into the environment and today the chemical nature, size and concentrations are poorly known. In order to provide new scientific knowledge in this field, a research project called “EMANE” associating the CSTB and the LNE aims to characterize the particle release as a function of various aging scenarios for TiO2 nano-additived paints.
In this study, a nanomaterial called “model paint” was performed in laboratory, composed of an acrylic paint and 5% in mass of nanoparticle of nano-TiO2 (Aeroxide® TiO2 P25 Evonik Degussa). The physicochemical properties were characterized for this “model paint”, and also for an acrylic paint and a commercial nano-additive photocatalytic paint. Samples of these three paints applied on the plasterboard plates (10x10 cm²) were submitted to different aging scenarios representative of environmental and use conditions encountered in indoor environments (humidity, temperature, oxidation, cleaning and mechanical solicitation).
The mechanical solicitations of samples were performed by abrasion by a TABER model 5750 linear Abraser. This device has a load arm which moves back-and-forth in a linear manner. The linear movement performed create a mechanical solicitation by friction at the tested material imply a particles released in the aerosol form. Test parameters such as stroke length, speed, load and the abrasive substrate used are adjustable. Two abrasion protocols have been developed. The first (stroke length = 7.6 cm, normal force = 8.3 N, velocity = 60 cycles/s, time = 30 s and cycles number = 30) corresponds to a strong abrasion removing the paint on the plasterboard plates and the second (stroke length = 7.6 cm, Normal force = 3.4 N, velocity= 75 cycles/s, time = 2 min and cycles number = 150) to a moderate with a partial abrasion of the paint. The abrasive substrate used (H18) is made of vitrified clay and has a diameter of 19 mm.
For each type of paint and scenario tested, three tests were carried out for each of the two abrasion protocols, corresponding a total of 165 experiments. In order to study the aerosol release associated with these two abrasion scenarios, the Taber abraser was installed in an experimental chamber to confine the aerosol and to move towards the aerosol emission to sampling isokinetic probes. The aerosols were characterized by real-time measurements (APS, DMS 500 and CNC3007) to measure the number concentration and the size distribution over a size range of 5 nm to 20 μm and by off-line measurements (MEB-EDX) carried out on aerosol samples.
The results obtained by DMS 500 and APS during abrasion on the “model paint” and on the commercial nano-additive paint samples show the emission of aerosols characterized by three particle populations around 60 nm, 200 nm and 2 μm. The results analysis shows the importance to normalize the number of particles emitted to the weight mass losses during an abrasion process for sample comparison. The study provide new scientific knowledge on the behavior of nanomaterials (TiO2 nano-additived paints) and especially on the aerosol released during mechanical solicitation. These new experimental data will allow us in the future to estimate the exposure of the people to manufactured nano-objects.