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VOC Emissions and Formation Mechanisms from Carbon Nanotube Composites during 3D Printing
Citation:
Potter, P., S. Al-Abed, D. Lay, AND S. Lomnicki. VOC Emissions and Formation Mechanisms from Carbon Nanotube Composites during 3D Printing. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 53:4364-4370, (2019). https://doi.org/10.1021/acs.est.9b00765
Impact/Purpose:
Polymers used in 3D printing are known to emit hazardous materials when heated. While the emissions from pristine polymers and some filaments have been studied, many filaments contain additives that may influence their hazardous emissions. For example, carbon nanotubes (CNTs) are added to some filaments to confer structural and electrical properties and are likely to interact with volatile organic compound (VOC) emissions. This research used a commercially-available CNT-containing 3D printer filament to investigate the effect of CNTs on VOC emissions during the printing process. While the presence of CNTs caused a slight overall decrease in the total VOC emissions, there was a shift towards more hazardous compounds being emitted. These findings should influence future studies on 3D printer emissions to include additives such as CNTs, metals, and dyes. These methodologies may be used by EPA's Chemical Safety and Pollution Prevention (OCSPP), Consumer Protection and Safety Commission (CPSC), and National Institute of Occupational of Safety and Health (NIOSH).
Description:
A commercially available, 3D printer nanocomposite filament of carbon nanotubes (CNTs) and acrylonitrile−butadiene− styrene (ABS) was analyzed with respect to its VOC emissions during simulated fused deposition modeling (FDM) and compared with a regular ABS filament. VOC emissions were quantified and characterized under a variety of conditions to simulate the thermal degradation that takes place during FDM. Increasing the residence time and temperature resulted in significant increases in VOC emissions, and the oxygen content of the reaction gas influenced the VOC profile. In agreement with other studies,the primary emitted VOC was styrene. Multiple compounds are reported in this work for the first time as having formed during FDM, including 4-vinylcyclohexene and 2-phenyl-2-propanol. Our results show that printing 222.0 g of filament is enough to surpass the reference concentration for inhalation exposure of 1 mg/m3 according to the EPA’s Integrated Risk Information System (IRIS). The presence of CNTs in the filament influenced VOC yields and product ratios through three types of surface interactions: (1) adsorption of O2 on CNTs lowers the available O2 for oxidation of primary backbone cleavage intermediates, (2) adsorption of styrene and other VOCs to CNTs leads to surface-catalyzed degradation, and (3) CNTs act as a trap for certain VOCs and prevent them from entering vapor emissions. While the presence of CNTs in the filament lowered the total VOC emission under most experimental conditions, they increased the emission of the most hazardous VOCs, such as α-methylstyrene and benzaldehyde. The present study has identified an increased risk associated with the use of CNT nanocomposites in 3D printing.
URLs/Downloads:
DOI: VOC Emissions and Formation Mechanisms from Carbon Nanotube Composites during 3D Printing
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