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Researchers from the U.S. Army Research Laboratory (ARL) are using recycled polyethylene terephthalate (PET) plastic, found in water bottles, yogurt containers, and other recyclable waste materials as 3D printing feedstock.

With such reclaimed materials, service members can utilize 3D printers within frontline bases to speedily fabricate replacement parts for military vehicles, weapons, and equipment. This practice will cut costs, shorten military supply chains, and increase the independence of troops on forward operating bases.

“Ideally, soldiers wouldn’t have to wait for the next supply truck to receive vital equipment,” said Dr. Nicole Zander, Research Chemist at the ARL.

“Instead, they could basically go into the cafeteria, gather discarded water bottles, milk jugs, cardboard boxes and other recyclable items, then use those materials as feedstocks for 3D printers to make tools, parts and other gadgets.”

Operational readiness through 3D printed waste materials

According to the U.S.Government Accountability Office, the U.S. Department of Defense (DoD) has an inventory of 5 million items, including food, fuel, ammunition and replacement parts, distributed through eight distinct supply chains. These items are often stockpiled at frontline bases causing material shortages for troops.

Although many of these bases are equipped with 3D printers to make replacement equipment such as hot cup handles and door latch components, the filament must be requisitioned which can take over a month to arrive. Thus, recognizing the strength of waste plastics, Dr. Zander, U.S. Marine Corps Capt. Anthony Molnar and ARL researchers began developing a process for converting such materials into 3D printing filament. Capt. Molnar stated:

“As our enemies have shown us, they can often outpace our ability to react to their new tactics and equipment. This new technology will enable the warfighter to more rapidly develop tools necessary to defeat an ever-changing enemy technology.”

The U.S Army Armament Research, Development and Engineering Center (ARDEC) has also previously integrated 3D printing to improve military readiness as seen with its portable 3D printing part replacement system, the PackBot.

Recycled composites

Using a process called solid-state shear pulverization, ARL researchers generated composite thermoplastic filaments. In this process, shredded plastic and paper, cardboard and wood flour was pulverized in a twin-screw extruder to create a fine powder. This powder was then melt-processed into 3D printer filament.

After testing, the researchers concluded that the new composites had improved mechanical properties, as well as improved strength for 3D printed materials. Dr. Zander added:

“In terms of mechanical properties, most polymers used in FFF have bulk strengths between 30 and 100 MPa[ megapascal]. Recycled PET has an average strength of 70 MPa, and thus may be a suitable 3D printing feedstock.”

Chemical testing of recycled filaments

The researchers tested the recycled PET filaments by printing a vehicle radio bracket, a long-lead-time military part, which used approximately 10 water bottles and took about two hours to complete.

ARL researchers and the U.S. Marine Corps are now collaborating to build a mobile recycling trailer for specially trained soldiers to fabricate 3D printing filaments from plastic waste. Dr. Zander is also seeking ways to print materials from plastic pellets instead of filaments, which could produce larger 3D printed parts and machinery.

“We still have a lot to learn about how to best process these materials and what kinds of additives will improve their properties,” said Dr. Zander. “We’re just scratching the surface of what we can ultimately do with these discarded plastics.”

This research will be presented at the 256th National Meeting & Exposition on August 23rd at the American Chemical Society (ACS), in Boston.

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Featured image shows Dr. Nicole Zander demonstrating the filament converting process for Capt. Anthony Molnar. Photo via U.S. Army/ Jhi Scott.