Detection and quantification of free carbon nanotubes in abraded polymer nanocomposites using UV-vis spectroscopy

Here we report a simple and rapid method to quantify free carbon nanotubes (CNTs) in the debris of abraded nanocomposites using ultraviolet-visible (UV-vis) spectroscopy. The method uses a surfactant to disperse free CNTs and separates out these via centrifugation from the CNTs that are aggregated, completely embedded in the polymer fragments, or protruding from the polymer fragments. The UV-vis spectroscopy is then used to measure the absorbance of the dispersed CNTs which is correlated to the total free CNT content in the debris via a calibration curve. We find that the method detects free CNTs in the debris of sanded CNT-epoxy composites. We also determine that when CNT-based anticorrosive paint is removed via sandblasting after its useful lifetime, no free CNTs are present above the detection limit of 1.3 x 10(-4) wt%. Finally, we also show that when various CNT-polylactic acid (PLA) coatings on three-dimensional (3D) printer PLA filaments are abraded, no free CNTs are found in the debris above the detection limit. In contrast to other methods of free CNT analysis, our method quickly provides reliable quantitative information about free CNT content which is useful for both industries and risk assessors in evaluating exposure potential of CNT-based products.