Multifunctional nanofiber protects against explosions, extreme temps
Material could protect soldiers, firefighters, astronauts and more

Date:
June 29, 2020
Source:
Harvard John A. Paulson School of Engineering and Applied Sciences
Summary:
Researchers have developed a lightweight, multifunctional nanofiber
material that can protect wearers from both extreme temperatures
and ballistic threats.



FULL STORY ========================================================================== Since World War I, the vast majority of American combat casualties has
come not from gunshot wounds but from explosions. Today, most soldiers
wear a heavy, bullet-proof vest to protect their torso but much of their
body remains exposed to the indiscriminate aim of explosive fragments
and shrapnel.


========================================================================== Designing equipment to protect extremities against the extreme
temperatures and deadly projectiles that accompany an explosion has been difficult because of a fundamental property of materials. Materials that
are strong enough to protect against ballistic threats can't protect
against extreme temperatures and vice versa. As a result, much of
today's protective equipment is composed of multiple layers of different materials, leading to bulky, heavy gear that, if worn on the arms and
legs, would severely limit a soldier's mobility.

Now, Harvard University researchers, in collaboration with the U.S. Army
Combat Capabilities Development Command Soldier Center (CCDC SC) and
West Point, have developed a lightweight, multifunctional nanofiber
material that can protect wearers from both extreme temperatures and
ballistic threats.

The research is published in the journal Matter.

"When I was in combat in Afghanistan, I saw firsthand how body armor could
save lives," said senior author Kit Parker, the Tarr Family Professor of Bioengineering and Applied Physics at the Harvard John A. Paulson School
of Engineering and Applied Sciences (SEAS) and a lieutenant colonel in
the United States Army Reserve. "I also saw how heavy body armor could
limit mobility. As soldiers on the battlefield, the three primary tasks
are to move, shoot, and communicate. If you limit one of those, you
decrease survivability and you endanger mission success." "Our goal was
to design a multifunctional material that could protect someone working
in an extreme environment, such as an astronaut, firefighter or soldier,
from the many different threats they face," said Grant M. Gonzalez,
a postdoctoral fellow at SEAS and first author of the paper.



==========================================================================
In order to achieve this practical goal, the researchers needed to
explore the tradeoff between mechanical protection and thermal insulation, properties rooted in a material's molecular structure and orientation.

Materials with strong mechanical protection, such as metals and
ceramics, have a highly ordered and aligned molecular structure. This
structure allows them to withstand and distribute the energy of a direct
blow. Insulating materials, on the other hand, have a much less ordered structure, which prevents the transmission of heat through the material.

Kevlar and Twaron are commercial products used extensively in protective equipment and can provide either ballistic or thermal protection,
depending on how they are manufactured. Woven Kevlar, for example,
has a highly aligned crystalline structure and is used in protective bulletproof vests. Porous Kevlar aerogels, on the other hand, have been
shown to have high thermal insulation.

"Our idea was to use this Kevlar polymer to combine the woven,
ordered structure of fibers with the porosity of aerogels to make long, continuous fibers with porous spacing in between," said Gonzalez. "In
this system, the long fibers could resist a mechanical impact while the
pores would limit heat diffusion." The research team used immersion
Rotary Jet-Spinning (iRJS), a technique developed by Parker's Disease Biophysics Group, to manufacture the fibers. In this technique, a liquid polymer solution is loaded into a reservoir and pushed out through a
tiny opening by centrifugal force as the device spins. When the polymer solution shoots out of the reservoir, it first passes through an area
of open air, where the polymers elongate and the chains align. Then the solution hits a liquid bath that removes the solvent and precipitates
the polymers to form solid fibers. Since the bath is also spinning --
like water in a salad spinner -- the nanofibers follow the stream of
the vortex and wrap around a rotating collector at the base of the device.



==========================================================================
By tuning the viscosity of the liquid polymer solution, the researchers
were able to spin long, aligned nanofibers into porous sheets -- providing enough order to protect against projectiles but enough disorder to
protect against heat. In about 10 minutes, the team could spin sheets
about 10 by 30 centimeters in size.

To test the sheets, the Harvard team turned to their collaborators to
perform ballistic tests. Researchers at CCDC SC in Natick, Massachusetts simulated shrapnel impact by shooting large, BB-like projectiles at the
sample. The team performed tests by sandwiching the nanofiber sheets
between sheets of woven Twaron. They observed little difference in
protection between a stack of all woven Twaron sheets and a combined
stack of woven Twaron and spun nanofibers.

"The capabilities of the CCDC SC allow us to quantify the successes of
our fibers from the perspective of protective equipment for warfighters, specifically," said Gonzalez.

"Academic collaborations, especially those with distinguished local universities such as Harvard, provide CCDC SC the opportunity to
leverage cutting-edge expertise and facilities to augment our own R&D capabilities," said Kathleen Swana, a researcher at CCDC SC and one of
the paper's authors.

"CCDC SC, in return, provides valuable scientific and soldier-centric
expertise and testing capabilities to help drive the research forward."
In testing for thermal protection, the researchers found that the
nanofibers provided 20 times the heat insulation capability of commercial Twaron and Kevlar.

"While there are improvements that could be made, we have pushed the
boundaries of what's possible and started moving the field towards this
kind of multifunctional material," said Gonzalez.

"We've shown that you can develop highly protective textiles for people
that work in harm's way," said Parker. "Our challenge now is to evolve
the scientific advances to innovative products for my brothers and sisters
in arms." Harvard's Office of Technology Development has filed a patent application for the technology and is actively seeking commercialization opportunities.


========================================================================== Story Source: Materials provided by Harvard_John_A._Paulson_School_of_Engineering_and_Applied
Sciences. Original written by Leah Burrows. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Grant M. Gonzalez, Janet Ward, John Song, Kathleen Swana, Stephen A.

Fossey, Jesse L. Palmer, Felita W. Zhang, Veronica M. Lucian,
Luca Cera, John F. Zimmerman, F. John Burpo, Kevin Kit
Parker. para-Aramid Fiber Sheets for Simultaneous Mechanical and
Thermal Protection in Extreme Environments. Matter, 2020; DOI:
10.1016/j.matt.2020.06.001 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200629120206.htm

--- up 22 weeks, 6 days, 2 hours, 38 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)