Faculty and graduate students in NC States Colleges of Textiles
(COT) are applying nanotechnology to add new technological capabilities
to protective clothing while lightening the burden shouldered by public
safety and defense professionals. In partnership with faculty in the
Colleges of Engineering and Physical and Mathematical Sciences, textiles
researchers are leveraging their unique and complementary strengths
in nanoscience, materials science and polymer, fiber and textile sciences
to the good of tomorrows heroes.
Smaller, Lighter, Stronger
Weve all seen the images of the World Trade Center firefighters
and police trudging slowly up the endless stairways lugging equipment
and weighed down by heavy fire suits and helmets. TV carries footage
of our soldiers shivering in the mountains of Afghanistan but reluctant
to add the weight of warmer clothes to the burden of the 130 pounds
of weapons, ammunition, rations, water, gas masks, communications
equipment and protective clothing they are already carrying. The technology
is available for soldiers and firefighters to protect themselves from
almost anything, if only they could carry it all. A typical firefighters
flameproof suit now weighs about 30 pounds without the addition the
air tank (another 30 pounds), axe, ropes, radio, or other gear. Hazardous
chemical and biological protection requires yet another heavy layer.
Weight reduction is a matter of life and death for the people who
risk their lives to protect the rest of us.
Channeling the Science
The mix of strengths in the COT provides a unique ability to develop
and adapt new classes of functional nanofibers, and to shape them
into lightweight, high-performance protective clothing. In an example
of fundamental research undergirding such new-age textiles, polymer
chemist Dr. Alan Tonelli has recently filed a patent for use of nanoscience
to create high-strength, lightweight nanofibers with multifunctional
properties. Were figuring out how to organize polymer
chain moleculesthe basic stuff of textile fiberfor higher
strength, higher melting points, and chemical and antibacterial impermeability,
says Tonelli. He and his graduate students are stacking cyclodextrin
molecules to form a nano-tubular compound that attracts polymer chains
and loads them down its middle channel (see illustration).
Dissolving the cyclodextrin coating then allows the stretched
and aligned polymers to crystallize on themselves and make very high-strength
fibers, Tonelli continues. Using this technique, we can
intimately mix polymers with different properties for the first time,
embedding other features such as fire retardancy or antibacterial
protection. These embedded features are superior to coatings, which
are not only heavy but also tend to wear or wash off.
While such mind-boggling nanoscience is happening in laboratory test
tubes, the next challenge is to scale up nanomaterials manufacturing
while preserving the embedded nano features. Scientists in the high-tech
manufacturing facilities in COTs Nonwovens Cooperative Research
Center (NCRC) are working on making Tonellis nanofibers into
fabric. NCRC director Dr. Benham Pourdeyhimi, explains the difficulty.
We cant process nanofibers by themselves because they
are invisible. It's like trying to weave spider webs. With highly
specialized NCRC equipment, Pourdeyhimi and colleague Dr. Trevor Little
can extrude the nanofibers in various combinations with other polymers
(see story on previous page), using hot air to blow and stretch them
into webs of nonwoven fabric.
But why the push to get the size of fibers down to the nanoscale?
Its all about porosity and the surface-area-to-weight
ratio, says Pourdeyhimi. The tiny pores between the tightly
packed nanofibers stop all but the very smallest molecules from getting
through. Also, the thinner the fabric, the less weight it adds.
No cutting. No sewing.
In a related project with the NCRC, Drs. Tushar Ghosh and Abdelfattah
Seyam are finishing up work on a $2.1 million research grant from
the Army Research Office. They have created a process for generating
lightweight battlefield chem-bio protection in just one step from
polymer extrusion to garment. A system called Robotic Fiber Assembly
and Control melt-blows fibers onto a mannequin, custom-molding a garment
with no seams. Further research is underway to incorporate electrospinning
technology with the system to reduce garment weights while increasing
Ghosh says the manufacturing scale-up of such a process would provide
a high-strength, low-cost, disposable, head-to-toe barrier that a
soldier could carry in his pocketdonning it over other clothing
in the event of a chemical or biological threat. With special polymers
such as those developed by Tonelli and a host of other top materials
scientists at NC State, such a garment might also provide flame resistance,
passive heating or cooling, or even chameleon-like camouflage. Additional
funding will be needed to improve the robotic process and deal with
scale-up issues related to manufacturing safety. But Ghosh and Seyam
already see other applications for the one-step process as diverse
as custom-fit shoes, car linings and industrial filters.
Most of the research in the College of Textiles is moving toward
new textiles rather than traditional manufacturing,
says Ghosh. There will be a day when what we now know as the
U.S. textile industry will be married to other high-technology areas
such as aerospace, electronics and transportation. Nanotechnology
is ushering in a new phase of the textile industry with a brighter
more information, please visit www.tx.ncsu.edu/extension/service/appres/appres.htm