The recent paper is an attempt at getting a clearer picture of particle emissions in 3D printing. As the authors mentioned, there have been several research studies on the environmental effects of 3D printing. But none had identified the chemical structure of the particles and organic compounds released from a 3D printer, during printing and in the stand by mode.
The paper was largely focused on characterizing the volatile organic compound (VOC), semi-volatile organic compounds (SVOC), and total volatile organic compounds (TVOC). Volatile organic compounds are organic chemicals (generally contain carbon) which vaporize at a low temperature and enter the surrounding atmosphere. Volatility refers to the tendency of a compound to vaporize.
VOCs are generally released from burning fuel like wood or coal, and consumer products like cigarettes, paints, and adhesives. Depending on the chemical, VOCs could be harmful or have no effect on the health at all. And adverse effects, especially from consumer products, can be countered by increasing ventilation.
In addition to characterizes VOCs released in the 3D printing process, the researchers also classified particle number concentration (PNS) and particle size distributor (PSD) of the VOCs.
The tests were carried out in a controlled environment. A 3 cubic meter steel chamber was designed to be used in the study which was built at Fraunhofer WKI and was compatible with ISO 16000-9 (2006), an indoor air standard to determine VOC emissions.
The chamber was optimized for the experiment, so that “the incoming chamber air was cleaned and filtered to remove organic compounds and particles. The chamber air was set to 23 °C and 50% relative humidity. The air exchange rate was set to 1.0 h−1 or 1.5 h−1.”
As it was a comparative study of various filaments, only one desktop 3D printer was used to carry out all the tests, the award-winning M200 by the Polish manufacturer Zortrax. Multiple filaments were used in the study, including ABS, ASA, HIPS, PETG and PCABS.
All the filaments were purchased from Zortrax and 3Dmensionals, a German retailer of 3D printing equipment.
The National Institute for Standards and Technology (NIST) test artifact was used as the base model for all tests.
Classification of VOCs
It was shown in the study that a 3D printer emits VOCs while heating up the bed at 55°C when no printing process is taking place. Most likely these compounds are part of the mechanical features of the 3D printer, such as metal component lubricants.
Each 3D print test was four-hour long. And after a thorough study, a table of classification of particle composition and emission rates was drawn.
Of all the materials tested PETG showed the lowest total emission rates, whereas ABS and ULTRAT-based filaments had the highest emission rates. Styrene, a colorless oily liquid, was found to be most common in all the filaments tested “except PETG-based filaments (PETG, GLASS and ESD).”
The study concluded: “To the best of our knowledge, we have demonstrated for the ﬁrst time that the particles emitted from a desktop 3D printer are semi-volatile and are composed of SVOCs which are mainly thermoplastic additives and cyclosiloxanes.”
Therefore, it was suggested that the composition of 3D printing filaments should be studied further and their composition improved.
“Our data, which supplement results from previous studies, lead to the conclusion that, regarding particulate and gaseous emissions, 3D printing technology and the chemical composition of filaments still need to be optimized.”