Additive manufacturing, more commonly known as 3D printing, has already found commercial application in various industries and its use is on the rise. 3D printing converts 3D digital models created on a computer or with a scanner into physical objects, usually by successively adding material layer by layer. The process allows manufacturers to make complex designs, rapid prototypes and final products while offering the potential to limit process waste and reduce production costs.
3D printing is no longer a novelty, as manufacturers in the automotive, aviation, medical, consumer goods, entertainment and numerous other industries are integrating 3D printing into their production processes. It is only a matter of time before the development of faster, more capable industrial 3D printers, as well as desktop 3D printers, makes the technology a household concept.
As with any evolving technology, 3D printing raises a host of environmental legal questions, surrounding, for example, hazardous waste, air emissions, recycling and chemical disclosure, just to name a few. Recently, 3D printing has caught the attention of the US Environmental Protection Agency (EPA).
Earlier this year, EPA scientists published a report on 3D printing filament additives and the potential release of volatile organic compound (VOC) emissions, and EPA has continued to build upon its findings in a recent article, Keeping up with 3D Printing: EPA Researchers Build on New Plastic Emissions Study (Sept. 10, 2019). While many studies have focused on the effects of VOCs from 3D printing, this was the first to consider how these emissions change when certain additives are introduced to the 3D printing filament.
EPA’s research focused on the potential effects of adding carbon nanotubes (CNTs) to filament composed of acrylonitrile-butadiene-sytrene (ABS)—a common polymer used in 3D printing. EPA was particularly interested in CNTs because they are increasingly being added to filaments to create electrical components due to their conductive and thermal properties.
EPA used a device known as the System for Thermal Diagnostic Studies (STDS) to test two filaments—one composed solely of ABS and one that contained CNTs—under a variety of conditions to simulate the heating, melting and forming of plastics that occur during 3D printing. The filament samples were tested at different temperatures, for different lengths of time and with different oxygen concentrations to replicate common printing conditions.
EPA’s study reached several conclusions:
- The ABS-CNT filament resulted in the emission of two additional VOCs—2,4-di-tert-butylphenol and 2,6-di-tert-butylquinone—that were not emitted by the ABS filament and which could pose an inhalation hazard to users printing several kilograms of material.
- The presence of CNTs in filament lowered the total VOC emissions under most conditions, but increased the amount of emissions from the most hazardous VOCS, including a-methylstyrene and benzaldehyde.
- Increased print temperature had the most significant effect on increasing VOC emissions, followed by increased length of time heating the materials.
- CNTs may “trap” certain VOC gases in the printed plastic.
EPA and the Consumer Products Safety Commission (CPSC) have stated that they will continue to investigate other popular filament additives to determine their possible effects on 3D printer emissions. They also stated the need for addition studies to understand the potential impacts on human health. This is likely the beginning of a much deeper dive for EPA into the 3D printing space.
This study, as well as EPA’s continued focus on emissions released from 3D printing, may have a dramatic effect on the evolution of this technology.
 The STDS is a custom-built, modular instrument that has previously been used to provide thermal conditions for combustion of various waste components.
 Results show that the presence of CNTs slightly decreased emissions of VOCs, except for when the sample was heated to 300° C/3 min/N2.