Faculty and graduate students in NC State’s 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 tomorrow’s heroes.

Smaller, Lighter, Stronger
We’ve 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 firefighter’s 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. “We’re figuring out how to organize polymer chain molecules—the basic stuff of textile fiber—for 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.”

Scaling-up
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 COT’s Nonwovens Cooperative Research Center (NCRC) are working on making Tonelli’s nanofibers into fabric. NCRC director Dr. Benham Pourdeyhimi, explains the difficulty. “We can’t 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? “It’s 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 protection.

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 pocket—donning 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 future.”

For more information, please visit www.tx.ncsu.edu/extension/service/appres/appres.htm