Evaluation of airborne particle emissions from commercial products containing carbon nanotubes

The emission of the airborne particles from epoxy resin test sticks with different carbon nanotube (CNT) loadings and two commercial products were characterized while sanding with three grit sizes and three disk sander speeds. The total number concentrations, respirable mass concentrations, and particle size number/mass distributions of the emitted particles were measured using a condensation particle counter, an optical particle counter, and a scanning mobility particle sizer. The emitted particles were sampled on a polycarbonate filter and analyzed using electron microscopy. The highest number concentrations (arithmetic mean = 4,670 particles/cm³) were produced with coarse sandpaper, 2 % (by weight) CNT test sticks and medium disk sander speed, whereas the lowest number concentrations (arithmetic mean = 92 particles/cm³) were produced with medium sandpaper, 2 % CNT test sticks and slow disk sander speed. Respirable mass concentrations were the highest (arithmetic mean = 1.01 mg/m³) for fine sandpaper, 2 % CNT test sticks and medium disk sander speed and the lowest (arithmetic mean = 0.20 mg/m³) for medium sandpaper, 0 % CNT test sticks and medium disk sander speed. For CNT-epoxy samples, airborne particles were primarily micrometer-sized epoxy cores with CNT protrusions. No free CNTs were observed in airborne samples, except for tests conducted with 4 % CNT-epoxy. The number concentration, mass concentration, and size distribution of airborne particles generated when products containing CNTs are sanded depends on the conditions of sanding and the characteristics of the material being sanded.