While opinions vary on exactly how small a fiber must be to classify as “nano,” the National Nanotechnology Initiative—an organization that expedites the discovery, development and deployment of nanotechnology—reports that typical dimensions lie between one and 100 nanometers, stating this range is where unique phenomena enable novel applications.
For nonwovens, these unique phenomena pose a number of key advantages to producers and end users, such as increased surface area and the ability to spin fibers in a continuous filament process. According to Seshadri Ramkumar, of the Nonwovens & Advanced Material Lab at Texas Tech University, the textile industry has focused on two aspects of nanotechnology: fibers and finishes. While nano-based products have encountered challenges related to productivity, performance, scale-up and cost, Ramkumar says he feels that advancements will continue in this market.
“The basic structures can be built-up further to develop higher order structures such as fabrics and composites where nanofibers and other fibrous structures can serve as building blocks,” he says. “The inherent characteristics of these nanomaterials such as high surface area and weight-to-volume ratio at the building block level will be of great advantage wherever high performance, life and environmental related end uses are involved.”
Adding that he feels cost will not be a concern in the healthcare, environmental, defense, aerospace and advanced technology sectors, Ramkumar predicts developments will provide immense opportunities for small- and medium-sized enterprises to venture into the field.
Currently, nonwovens-based applications being enhanced by the use of nanofibers include filtration and energy storage applications, but experts believe the benefits of nanotechnology range from wrinkle resistance, inhibiting bacterial growth and even ballistic energy deflection in personal body armor. Additionally, nanofibers are opening up new doors to nonwovens, such as in the light fixture market, and some say these fibers could find their way into virtually any market for nonwovens.
According to Tony Fedel, associate marketing director of Kimberly-Clark Partnership Products, his company is constantly looking at nanotechnology for ways to expand its existing business. However, so far many developments are still in the infancy stage.
“It’s one of those things where the idea of getting to that level of fiber, I think, will hold a lot of benefits, ultimately, from a sustainability factor where you can do more with less; but I have not really seen it revolutionizing anything yet,” he says. “The thing is, creating nanofibers is still in its infancy. There are a lot of technical hurdles that people around the industry are trying to crack. A lot of this has to do with economies.”
PGI Steps In
While the bulk of its business continues to lie within the spunmelt market, targeting hygiene applications, Polymer Group Inc. (PGI) recently developed a nanofiber-based nonwovens technology that could ultimately find a place in a wide range of nonwoven products, including healthcare, industrial, filtration and new emerging market applications.
Reporting that Arium technology produces a matrix of fibers predominately sized under one micron in diameter, CEO Veronica Hagen says, “Arium is a completely new technology platform for the industry that will enable us to meet the market need for increasingly cost-effective fabrics with improved performance at a value proposition unmatched by any other submicron fiber technology.”
This “game-changing technology features an improved process of producing submicron fibers that is the result of significant research and development efforts,” Hagen adds.
According to Bob Dale, PGI’s senior vice president of research and development, “While other processes can generate fibers at the submicron level, none can do it as efficiently, and with the same commercial level of throughputs, as Arium technology.”
Launched in late 2011, PGI has already begun making Arium products on a pilot line at its Waynesboro, VA, facility. The technology can stand alone or be retrofitted to PGI’s existing meltblown equipment. This technology will allow PGI to be more competitive in its core markets while also opening up new opportunities in other areas, whether it stands alone or is used with other nonwovens technologies, according to the company.
The submicron fibers contained in materials produced with the Arium technology can provide higher surface area, biosafety and porosity that enhance performance benefits such as absorbency, adsorption, opacity, softness, barrier protection, acoustic performance and high-efficiency filtration.
Another nonwovens producer that has been working hard to develop nano-based technologies is Hollingsworth & Vose (H&V). The Walpole, MA-based company has a number of commercial applications targeting the filtration market that rely on nano-sized fibers. Successes include glass and synthetic comprised materials such as glass fiber media for HEPA and ULPA applications, which have been using nanofibers for decades. “These media combine surface and depth filtration properties,” says Angelika Mayman, director of business development. “Glass fiber media of this kind have very high specific surface area, which is a major advantage for cleanroom applications and indoor air quality (IAQ) improvement.”
Among H&V’s nano-based products is Nanoweb for air and liquid filtration, which offers submicron efficiency, low pressure drop and high performance against soot. It is available for standalone webs or as a coating on nearly any substrate.
NanoWave is another offering for commercial HVAC applications. NanoWave is a synthetic alternative to glass mat media that offers increased sustainability and high discharge efficiency. Produced with a single polymer, the media’s stiff design results in enhanced processability and creates rigid pockets for filtration. Combining low pressure drop and high dust holding capacity allows NanoWave to fit a broad range of applications for the HVAC market. When charged, NanoWave provides increased submicron particle retention as well as higher minimum efficiency reporting value (MERV) classification.
While nanofibers clearly pose a number of advantages to many applications, Mayman adds they still need a little help. “Many end users in the market believe that simply adding a nanofiber layer to existing materials will offer a significant advantage,” she says. “It is the optimized combination of nanofiber materials and the base layer which can provide an advantage, as there are many factors to consider, including compatibility of the materials, adhesion of one layer to another and choice of nanofiber diameter.”
The Light Choice
Researchers at RTI International have used nonwovens technology to apply nanofibers to the lighting industry, developing a product that can increase the reflectivity in light fixtures, providing 40% more light without increasing energy output. Called NLITe, the technology works in any lighting fixture, from traditional fluorescents to emerging energy efficient LED-based fixtures.
“This is an exciting new technology for the lighting market based on nonwovens,” says Galen Hatfield, vice president of commercial programs for RTI International, a North Carolina-based non-profit research institute. “We have received tremendous response from nonwovens producers, not only because this is an opportunity to bring nonwovens into a new space where they don’t play, but also because it is a high-end technical product that can drive higher margins.”
In the new technology, the nonwoven creates a reflectance higher than 95% and replaces traditional coatings, such as paint or aluminum, which can have reflectance values below 80%. By improving the light output by as much as 40%, NLITe offers improved energy efficiency, as well as lower installation, operating and energy costs.
Hatfield explains that light fixtures outfitted with NLITe are brighter because the small fibers diffuse the light across a range of surfaces in the same way freshly fallen snow reflects sunlight. The material can also be modified to adjust the color palette of the light. In this technology, the nanofiber’s small size allows it to reflect light out in many directions. In examining a way to apply nanofiber technology to increase lighting efficiency, RTI researchers looked at a number of processing technologies, but ultimately decided nonwovens were the best avenue.
RTI developed the technology using funding from the U.S. Department of Energy. The project originally set out to develop a key technology to improve the efficiency and performance of solid-state lighting as a means to help manage energy consumption in the U.S.
Solely a research firm without the ability to sell products on its own, RTI International is now working on a business plan for the new technology and expects to have the product commercialized—in one way or another—within the next year. “I don’t think we’ll have enough material to coat every fixture in America but we should be able to seed the market with select applications within the next 12-18 months,” Hatfield says. “We were thrilled at the excitement we heard from nonwovens producers.”
RTI has already partnered with a major nonwovens producer to co-develop the NLite technology and bring products to market. While the technology has just begun the sampling stage this summer, it is already getting a lot of traction in the marketplace.
NTI is one of many research-oriented firms or universities that are focusing on nanotechnology. Researchers at Texas Tech are developing cotton nanofiber composites with enhanced filtration capabilities.
Xungai Wang, a professor at the Center for Material and Fiber Innovation at Deakin University in Australia is working on a new form of solvent spinning to make electrospun nanofibers featuring uniform fiber distribution, higher production capability and simple operating procedures. Additionally, the Nonwovens Institute at NC State in Raleigh, NC, has focused heavily on nanofibers and has even sponsored a conference dedicated to the technology.
Speaking about the future of nanofibers, Hatfield says the beauty of the technology is its dependence on the fiber structure, not the method of production. “We have worked with people who use a variety of different manufacturing processes and we believe the technology is very versatile,” he says.