Research Teams Are Developing New Materials to Safeguard Soldiers and First Responders
By Ed Brennen
At the High Bay Plastics Manufacturing Center in the Saab Emerging Technologies and Innovation Center on North Campus, two research teams from the Francis College of Engineering are developing new materials to help better protect people from exposure to dangerous chemicals and fire.
They’re a stone’s throw from where the university began training textile industry workers almost 125 years ago, but lightyears away from the cotton and wool that students once learned to manufacture on steam-powered looms. Today, UMass Lowell students and faculty are developing bicomponent fibers and multilayer elastomers on state-of-the-art extruders – work that they hope will one day save lives.
Call it a return to the university’s textile roots?
“Absolutely,” says Assoc. Prof. of Plastics EngineeringStephen Johnston, who is the principal investigator on a project that aims to produce bi-component fibers that can make the military’s Flame Resistant Army Combat Uniforms less expensive and, in turn, more widely available to soldiers.
Another project, led by Distinguished University Professor Joey Mead of the Plastics Engineering Department and Assoc. Prof. of Mechanical EngineeringChristopher Hansen, involves the development of multilayer elastomers to enhance the chemical-resistance properties of the protective gear worn by first responders and chemical plant workers and make the suits more flexible.
Both projects are part of the university’s HEROES (Harnessing Emerging Research Opportunities to Empower Soldiers) initiative. They are funded by the U.S. Army Combat Capabilities Development Command Soldier Center (CCDC SC), which was formerly known as the U.S. Army Natick Soldier Research, Development and Engineering Center.
Much of the protective gear currently on the market, such as hazmat suits and gloves, is typically made of thermoplastic layers that are not very flexible. For the past two years, Mead and Hansen, along with graduate student Jianan Yi and postdoctoral researchers Erin Keaney and Jinde Zhang, have been working to develop multilayer elastomers that could be used in protective gear to provide better chemical resistance and flexibility.
With $200,000 in annual funding from the CCDC SC and the purchase of a new Brabender extruder, the team is working on a three-layer system using nitrile rubber, butyl rubber and the fluoroelastomer material FKM.
“We could go with more, but three looked like the best option for covering a broad range of chemicals,” says Mead, who is collaborating on the project with Walter Zukas, a research chemical engineer at the CCDC SC. Mead worked with Zukas at the U.S. Army Research Laboratory in Watertown before joining UMass Lowell in 1997.
Working with three layers has presented the challenge of keeping the final product from being too thick. And there’s also the question of how to get the layers to stick together.
“The multiple layers have to bond to each other properly; otherwise, they will not stay together as a single material,” Hansen says. “It’s a nontrivial effort.”
Mead says they’ve come up with some “unique methodologies” to solve the problem.
“The potential risk,” Yi says, “is the extra layer may increase the thickness, so we are trying to make it as thin as possible.”
Keaney, who serves in an advisory role on the project, says that cost is one of the benefits to this approach.
"He’s using the same materials without any additives, so you’re not spending money on additional materials and chemicals,” she says.
Yi, who presented his work at the International Elastomer Conference in Cleveland in October, is excited about the project’s potential.
“It’s fantastic trying to address challenges so we can protect soldiers and first-responders better,” he says. “Our target is not only in the lab; we want to scale up the process.”
“It’s really interesting work,” Mead adds. “It showcases some of the unique capabilities we have in our elastomer program at UMass Lowell.”
While the Army has been working to develop low-cost, flame-protective combat gear for decades, Johnston says the current version, introduced in 2007, has several drawbacks. Not only is it about twice as expensive as standard-issue combat uniforms made of nylon and cotton, but it contains a flame-retardant rayon that must be produced overseas because it does not meet Environmental Protection Agency standards.
Tom Tiano, a research chemist at the CCDC SC, knew that UMass Lowell had a fiber extrusion line that could be used to improve the material. “We need to get this done,” Tiano told Johnston several years ago. “Can you do it?”
The project soon became part of the HEROES initiative. Now in its third year, it has received $242,000 in funding from the CCDC SC, with an additional $90,000 under evaluation.
“It’s really a great team effort between the Army and the university,” says Johnston, who notes that Tiano and his colleague, Michael McPartlin, have been integral members of the team. “This has been a very collaborative project, where they have taken a very hands-on approach. And because of that, we’re always on the same page.”
One of the Army’s requirements for the project was to keep nylon in the fiber because it’s strong, long-lasting and easy to dye. So, Johnston’s team of graduate and undergraduate researchers spent much of the project’s first year in 2017 identifying viable flame-resistant compounds that wouldn’t degrade at the high temperatures required to process nylon. They settled on Nofia, a thermally stable compound made by FRX Polymers.
The next step was to combine the Nofia with nylon. They originally tried to mix the components, which created a chemical reaction that Johnston calls a “disaster.”
“The flame retardant causes the nylon to crosslink, so when you melt-mix them together, it comes out like burnt, ground-up oatmeal,” Johnston says. “It’s pretty disgusting.”
So, the team turned to the novel approach of developing bi-component fibers. The fibers have a “sheath-core” configuration (picture the cross section of a corn dog), with an outer layer of nylon fiber surrounding a fiber core containing the flame-resistant compound.
To make the core, the team used twin-screw extrusion lines to mix Nofia with polyethylene terephthalate (PET), a carrier resin commonly used to make polyester fibers. Once spun into a mono-component fiber, the researchers knitted small swatches of fabric for vertical flame testing by the Army.
“The knitted sample showed better flame performance than raw PET, which is promising,” says Johnston, whose team then moved on to making spools of the bi-component core sheath material using the fiber extrusion line at the Saab ETIC facility.
“This year, we’ve really validated the bi-component format, and we’re now scaling it up into manufacturing lots of spools of material,” Johnston says.
In his office at Ball Hall, Johnston holds up a bobbin that has about 4 kilometers of yarn. Creating those bobbins isn’t easy. The finished yarn consists of 144 “ends” that are created by combining six smaller spools of 24 fibers each. When things are running smoothly, it can take 3 to 4 hours to create a single 4-kilometer yarn. The spools of fiber are taken to the university’s Fabric Discovery Center and twisted into yarns, which are then sent to the Army for flame testing.
“To use production equipment for pilot level research is incredibly difficult,” says Johnston, who notes that his current team – Ph.D. student Chris Souza, master’s student Gabrielle Perez de Aldrete and undergrads Caitlin Janielis and Hadyn Beirnerun – run the fiber extrusion line about once a week, sandwiched by a day for setup and a day for teardown and cleanup.
“I’ve definitely gained a lot more hands-on experience with getting the extruder to run the way we want it to,” says Souza, a Billerica native who earned his bachelor’s degree in plastics engineering last spring and is in the first year of the Ph.D. program. “Before, I just had surface-level knowledge of what an extruder did. By cleaning it and taking apart the gear pumps for maintenance, I know this machine inside out now.”
Souza recalls letting out a loud “Whoop!” the first time he got some fiber samples spinning.
“It can be incredibly frustrating when you don’t get the samples, but that also makes it more rewarding when we do,” he says.
Perez de Aldrete plans to work in the medical device field after completing her master’s degree in polymer and plastics engineering. The Carlisle native likes knowing that the research work she’s doing has a bigger purpose.
“It’s really cool to know that our work can help make uniforms that can save people’s lives,” she says.
“I’m hopeful for the results,” says Johnston, who points out that the project doesn’t intend to compete with the expensive, high-end uniforms worn by firefighters. “We’re trying to improve the current combat fatigues by some percentage.”
But like the work being done by Mead and Hansen’s team on multilayer elastomers, the bi-component fiber research has the potential for a broader application.
“If successful, the fiber could be used to make garments for first-responders, construction workers and others,” Johnston says. “A modest improvement in flame-retardant performance could be very impactful.”