Particles Emission from an Industrial Spray Coating Process Using Nano-Materials
Benedetta Del Secco, Sara Trabucco, F. Ravegnani, Antti Joonas Koivisto, Ilaria Zanoni, Magda Blosi, Simona Ortelli, Marko Altin, Gianni Bartolini, Anna Luisa Costa, Franco Belosi
Abstract
Industrial spray coating processes are known to produce excellent coatings on large surfaces and are thus often used for in-line production. However, they could be one of the most critical sources of worker exposure to ultrafine particles (UFPs). A monitoring campaign at the Witek s.r.l. (Florence, Italy) was deployed to characterize the release of TiO2 NPs doped with nitrogen (TiO2-N) and Ag capped with hydroxyethyl cellulose (AgHEC) during automatic industrial spray-coating of polymethyl methacrylate (PMMA) and polyester. Aerosol particles were characterized inside the spray chamber at near field (NF) and far field (FF) locations using on-line and off-line instruments. Results showed that TiO2-N suspension produced higher particle number concentrations than AgHEC in the size range 0.3–1 µm (on average 1.9 102 p/cm3 and 2.5 101 p/cm3, respectively) after background removing. At FF, especially at worst case scenario (4 nozzles, 800 mL/min flow rate) for TiO2-N, the spray spikes were correlated with NF, with an observed time lag of 1 minute corresponding to a diffusion speed of 0.1 m/s. The averaged ratio between particles mass concentrations in the NF position and inside the spray chamber was 1.7% and 1.5% for TiO2-N and for AgHEC suspensions, respectively. The released particles’ number concentration of TiO2-N in the size particles range 0.3–1 µm was comparable for both PMMA and polyester substrates, about 1.5 and 1.6 102 p/cm3. In the size range 0.01–30 µm, the aerosol number concentration at NF for both suspensions was lower than the nano reference values (NRVs) of 16·103 p/cm-3.