Influence of spray-coating process parameters on the release of TiO2 particles for the production of antibacterial textile

Abstract

Titanium dioxide (TiO2) nanoparticles (NPs) are produced in high volume and widely used in manufacturing processes, raising potential occupational health concerns. Here, workers' exposure was assessed during production of antibacterial textiles, where TiO2 NPs were impregnated onto 65% polyester 35% cotton textile surface by spray-coating. The influence of pressure, web speed and number of working spray nozzles to TiO2 particles release was studied under different experimental conditions. Real-time monitoring was used to measure size-resolved particle concentration and lung-deposited surface area (LDSA) concentration using an optical particle counter and a diffusion charger, respectively, from both near- and far-field. Particles were sampled from the working area for off-line electron microscopy characterization, and suspensions of sampled particles were characterized by dynamic light scattering. Post-campaign data analysis was carried out and used for quantitative exposure safety assessment. Particle number concentration and LDSA results showed that pressure at the spraying nozzles (P) is the main parameter that influences the release of particles in the environment. Other process parameters studied (web speed and number of working spray nozzles) did not appear to significantly affect the release of particles. The particle number concentration in default experimental conditions (intermediate values for all process parameters; P = 2.3 bar, web speed = 6 m/min and number of working spray nozzles = 2) was quantified as 1.19 106 # L−1. Upon increasing the pressure, from 1.5 to 4.0 bar, near-field average mass and LDSA concentrations increased from 0.90 to 1.76 mg/m3, and from 51.8 to 290.5 μm2/cm3, respectively. Average (avg) mass concentrations were well below the maximum recommended exposure limit of 2.4 mg/m3 for fine TiO2 particles proposed by the US National Institute for Occupational Safety and Health.