The US Army is exploring ways to convert discarded plastic bottles into recycled PET filament. Soldiers will become even more self-sufficient in the battlefield by 3D printing useful spare parts from waste material.
A collaboration between the US Army Research Laboratory and the US Marine Corps has resulted in the discovery of using waste plastics — such as water bottles, milk jugs and yogurt containers — for 3D printing parts that soldiers may need on the battlefield.
Recycled plastics could be a valuable source of material for additive manufacturing in the US Army. Not only would it improve the self-reliance of service members on forward operating bases, it would also cut costs and reduce demand for the resupply of parts.
“The potential applications for additive manufacturing technologies are extensive,” says ARL researcher Dr. Nicole Zander. “Everything from pre-production models and temporary parts to end-use aircraft parts and medical implants.”
Additive manufacturing offers many advantages over traditional manufacturing, including increased part complexity and reduced time and cost to produce one-off items, such as a bracket for a radio.
The research by Zander and Captain Anthony Molnar from the U.S. Marine Corps generated filament from 100 percent recycled polyethylene terephthalate (PET) from bottles and plastics without any chemical modifications or additives. This filament can then be used in fused deposition modeling (FDM) 3D printers.
Work is also underway to generate filament from other recycled plastics and reinforced filaments. Zander says that while PET is widely used in many applications, it is not widely used as a “feedstock” for FDM because of difficulties like high melting temperature, moisture absorption, and issues with crystallization.
US Army Developing Mobile Recycling Facility for Battlefield 3D Printing
Molnar, project officer with the mobility and counter mobility team in Quantico, Virginia, argues that PET plastics such as water bottles and packaging are one of the most prolific wastes found on the battlefield.
Both US and coalition forces produce large volumes of this waste, and being able to repurpose this on location will reduce the logistic burden of transporting parts to forward operating bases. Not to mention the additional costs of disposing of the recyclable material.
To this end, Zander and Molnar are in the process of building a mobile recycling facility so that soldiers will be able to repurpose plastics into feedstocks for 3D printing.
“The MRF will be a plastic processing laboratory housed in a 20-foot ISO container, with all equipment and tools needed to fabricate 3D printing filament from plastic waste,” Zander says.
The researchers have determined that recycled plastics have shown to be suitable material for 3D printing, provided the material is properly cleaned and dried. The tensile strength of printed parts from recycled PET was equivalent to printed parts made from commercial off the shelf PET pellets and commercial filaments. But the work will not stop here.
Zander said blending with other plastics, or the addition of fillers such as reinforcing or toughening agents, may further improve the mechanical properties of the recycled plastic filament and expand the realm of applications in how it may be used.
“Ultimately, we’d like to produce the best possible feedstock we can from recycled plastics and waste materials,” Zander explains.
“Future work will involve testing select 3D printed long-lead parts against original parts to determine if they can be a suitable long-term or at least a temporary replacement.”
Source: Press Release