Safer, more comfortable soldier uniforms are in the works

Date:
August 17, 2020
Source:
American Chemical Society
Summary:
Uniforms of U.S. Army soldiers must feel comfortable in all
climates, be durable through multiple washings, resist fires and
ward off insects, among other things. Existing fabrics don't check
all of these boxes, so scientists have come up with a novel way
of creating a flame-retardant, insect-repellent fabric that uses
nontoxic substances.



FULL STORY ========================================================================== Uniforms of U.S. Army soldiers must meet a long list of challenging requirements. They need to feel comfortable in all climates, be durable
through multiple washings, resist fires and ward off insects, among
other things.

Existing fabrics don't check all of these boxes, so scientists have
come up with a novel way of creating a flame-retardant, insect-repellent
fabric that uses nontoxic substances.


==========================================================================
The researchers will present their results today at the American Chemical Society (ACS) Fall 2020 Virtual Meeting & Expo.

"The Army presented to us this interesting and challenging requirement for multifunctionality," says study leader Ramaswamy Nagarajan, Ph.D. "There
are flame-resistant Army combat uniforms made of various materials that
meet flame retardant requirements. But they are expensive, and there are problems with dyeing the fabrics. Also, some of the raw materials are not produced in the U.S. So, our goal was to find an existing material that we could modify to make it flame retardant and insect repellent, yet still
have a fabric that a soldier would want to wear." Because Nagarajan's
research group focuses on sustainable green chemistry, the team sought
nontoxic chemicals and processes for this study. They chose to modify a commercially available 50-50 nylon-cotton blend, a relatively inexpensive, durable and comfortable fabric produced in the U.S. The material is used
in a wide range of civilian and military applications because the nylon
is strong and resistant to abrasion, whereas the cotton is comfortable
to wear.

But this type of textile doesn't inherently repel bugs and is associated
with a high fire risk.

"We started with making the fabric fire retardant, focusing on the cotton
part of the blend," explains Sourabh Kulkarni, a Ph.D. student who
works with Nagarajan at the University of Massachusetts Lowell Center
for Advanced Materials. "Cotton has a lot of hydroxyl groups (oxygen
and hydrogen bonded together) on its surface, which can be activated by
readily available chemicals to link with phosphorus-containing compounds
that impart flame retardancy." For their phosphorus-containing compound,
they chose phytic acid, an abundant, nontoxic substance found in seeds,
nuts and grains.

Next, the researchers tackled the issue of making the material repel
insects so that soldiers wouldn't have to spray themselves repeatedly
or carry an additional item in their packs. The team took permethrin,
an everyday nontoxic insect repellent, and attached it to the fabric
using plasma-assisted deposition in collaboration with a local company, LaunchBay. Through trial and error, the researchers eventually got both
the phytic acid and permethrin to link to the fabric's surface molecules.

Using methods to measure heat release capacity and total heat release,
as well as a vertical flame test, they found that the modified material performed at least 20% better than the untreated material. They also
used a standard insect repellency test with live mosquitoes and found
that the efficacy was greater than 98%. Finally, the fabric remained "breathable" after treatment as determined by air permeability studies.

"We are very excited," Nagarajan says, "because we've shown we can
modify this fabric to be flame retardant and insect repellent -- and
still be fairly durable and comfortable. We'd like to use a substance
other than phytic acid that would contain more phosphorus and therefore
impart a greater level of flame retardancy, better durability and still
be nontoxic to a soldier's skin.

Having shown that we can modify the fabric, we would also like to see
if we can attach antimicrobials to prevent infections from bacteria,
as well as dyes that remain durable."

========================================================================== Story Source: Materials provided by American_Chemical_Society. Note:
Content may be edited for style and length.


==========================================================================


Link to news story: https://www.sciencedaily.com/releases/2020/08/200817104309.htm

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