From Plastic Waste to a Valuable Resource
3D Filament from Post-Consumer PET Used to 3D Print Spare Parts
PET plastics such as water bottles and packaging are one of the most prolific wastes found on the battlefield. U.S. and coalition forces produce large volumes of this waste. A collaboration between the U.S. Army Research Laboratory and the U.S. Marine Corps shows, how useful a used plastic water bottle might be for the military.
The study of the potential applications is being led by U.S. Army Research Laboratory (ARL) researcher Nicole Zander and Capt. Anthony Molnar of the U.S. Marine Corps. So far, research has resulted in the production of a 3D filament made of 100 % recycled PET from bottles or containers without any chemical modifications or additives.
Zander said that while PET is widely used in many applications, it is not widely used as a feedstock for fused filament fabrication (FFF) due to its high melting temperature, water absorption and issues with crystallinity, which can make printing difficult. "In terms of mechanical properties, most polymers used in FFF have bulk strengths between 30 and 100 MPa. Recycled PET has an average strength of 70 MPa, and thus may be a suitable 3D printing feedstock," Zander explains.
Mechanical testing, including uniaxial tensile and three point bending experiments were conducted in the laboratory. In these tests, the tensile strength of 3D printed recycled PET was compared against commercial filaments and found to have similar strength. In addition, a custom test fixture was made to test a 3D printed radio bracket (a long-lead military item). Brackets made from recycled PET failed at a similar load to brackets printed with commercial ABS filament. The recycled PET filament may have the capability to replace commercial filament in printing a diverse range of plastic parts.
Steve Post, business development manager for Thermo Fisher, the maker of the equipment the Army used to produce its filament, said this is a strong statement on sustainability. "The Army really thought out of the box on this application, turning a troublesome waste product into a valuable resource," he said.
In addition to mechanical testing, the recycled plastics underwent chemical analysis, thermal stability and a host of other tests. "Recycled polymers have a variety of different additives, fillers and dyes and may have experienced different processing conditions – even for the same polymer type," Zander said.
To get a better understanding of different recycled plastic feedstocks and the best properties to expect from such materials, chemical, thermal and mechanical analyses were performed.
Researchers said the driving force for this work is to enhance warfighter capability and readiness by enabling repairs while deployed and to reduce dependence of the logistical supply chain. Zander and Molnar are in the process of building a mobile recycling facility to enable soldiers to be able to repurpose plastics into feedstocks for 3D printing.
"How useful might that used plastic water bottle be for the military?" Click here for the YouTube video .