The U.S. National Nanotechnology Initiative defines nanotechnology as “the science, engineering and technology conducted at the nanoscale—about 1-100 nanometers.” Scientists have been conducting research at the nano level for decades; in fact, wetlaid glass media has been using nanofibers for more than 70 years. Until recently, scientists had difficulty measuring and manipulating parameters at the nano scale. Nanotechnology is a new tool to unlock endless potential for how we currently treat, process and use materials. It is like getting glasses for the first time and being able to see what we didn’t know was always there—just beneath the surface.
A recent market study by RNCOS, an industry research firm, predicts that the global market for nanotechnology, which includes nanomaterials, nanotools and nanodevices, to be $48.9 billion in 2017. Nanomaterials alone are expected to have sales worth $37.3 billion in 2017 followed by nanotools at $11.4 billion. As with any new significant scientific development, there are great opportunities for research, breakthrough and business.
To see how the industrial nonwovens industry is studying and using nanotechnology, I reached out to Christina Ruiz, Technology Scout with Hollingsworth & Vose, a global leader in the supply of technically advanced nonwovens for engine, high efficiency and liquid filtration.
Colleen Walker: How has nanotechnology impacted industrial nonwovens?
Christina Ruiz: Nanotechnology has brought both challenge and opportunity to industrial nonwovens. The ability to reliably manufacture materials at the nano scale has created product development opportunities not previously possible; and, as learning to measure at the nano scale improves, product performance demands increase. As with many things nano, it has been found that commonly used materials show very different, typically enhanced, physical properties at the nano scale compared to their bulk properties. Existing manufacturing processes have been pushed, new processes developed, and there’s still much more to come.
The launch of new nonwoven products enabled by nanotechnology is increasing in pace as understanding of the properties and benefits continues to rise. Nanotechnology integration requires a new and different knowledge set, pressuring industrial nonwoven suppliers and their customers to keep up with advances, learn to integrate the nanofibers into product design, all while showing measurable performance enhancements.
Walker: What types of fibers exist at the nano scale?
Ruiz: Much of the nanotechnology currently employed in industrial nonwovens is in the form of nanofibers, or more specifically, fibers with diameters at the nano scale. Materials being formed into nanofibers vary widely, from olefinic polymers to ceramics like lithium titanate. Naturally occurring materials are being processed down to the nano scale as well. These can be formed by many different processes; some processes have broad capability to produce several types of materials, while others are quite specific. Nanocellulose, in the pure crystalline form or the highly fibrillated form, yet another altogether different process, has reached commercial scale production and is finding broader adoption. Each of the materials mentioned is produced by different means, creating a multitude of new product opportunities and, at the same time, a significant challenge for the product developer. Which nanofiber material to employ, and so which process to invest in, these are among the questions being considered by our industry around the utilization of nanotechnology in the form of a nanofiber.
Common nanofibers employed include polyamides, polyvinylidene fluoride, polypropylenes, and polyesters. Polyamide (PA6, nylon) and polyvinylidene fluoride (PVDF) nanofibers are usually produced by a form of solution spinning, coupled with either centrifugal or electrical forces to enhance the drawing of the fiber down to nano scale diameters. Much of the foundational work in electrospinning nanofibers was done with polyamide chemistry and there is a strong public knowledge base on this chemistry in this process. That however, is not the case with many systems.
Polypropylenes (PP) and polyesters (PET, PBT) are commonly produced with nano scale diameters via polymer melt processes, including melt spinning, melt blowing and islands-in-the-sea type techniques. These techniques directly form polymer pellets into fibers by an extrusion process that is typically coupled with other forces to draw the fibers to the nano scale. In melt spinning, centrifugal force is used to draw the fiber while in melt blowing jets of air draw the fiber down to the nano scale range. In the case of an islands-in-the-sea type of technique, fibers are extruded at diameters in the micron range, and then split into sub-components, which will have diameters in the nano scale range.
Walker: What types of end uses and applications are currently using nanotechnology?
Ruiz: Filtration applications lead in the commercial implementation of nanofibers in industrial nonwovens. Air filtration end uses range from domestic to industrial HVAC systems. Automotive fluids such as oil and fuel are benefitting from the unique combination of a very thin nanofiber nonwoven and its inherent high surface area. Energy storage devices—including batteries, fuel cells and super capacitors—employ nanofibers in nonwoven separators and anodes. Medical end uses showing promise include applications for wound dressings, bone scaffolding and controlled release drug delivery. Applications that will benefit from nanofiber integration are those where high surface area combined with little additional volume or weight is desired.
Walker: What are some potential areas where nanotechnology can be used to develop new products for industrial nonwovens? And what are the challenges and opportunities in these areas?
Ruiz: Industrial nonwovens serve a multitude of applications and uses from a component in a bandage on a child’s knee to protecting the hydraulic fluid in a construction dozer to face masks for surgeons. What all of these applications share in common is that they enhance the human condition. Major challenges on the horizon include water scarcity and climate change. Both of these challenges can be addressed by the nonwovens industry.
Water scarcity is already an issue in many parts of the world and the urgency of the issue will rise as populations continue to increase. Clean drinking water is fundamental for health and many solutions exist today for cleaning water supplies. The sad irony here though is that many areas most in need of clean water are the least able to afford today’s technical solutions. Nanotechnology presents unique opportunities for the enhancement of the performance of an industrial nonwoven to create new products for the production of potable water.
Climate change, air pollution and associated negative health effects are another area that nanotechnology in nonwovens has an opportunity to impact quality of life. Recent journal articles have published findings that black carbon soot is a more impactful form of pollution than previously thought with regard to climate change. In fact, carbon soot is now ranked second only to carbon dioxide and is rated at roughly two thirds as impactful. Carbon soot particles contribute to warming directly, by absorbing radiation from the sun and raising the surrounding temperature. This overall temperature increase is believed to, in turn, impact ice and snow melt rates. Carbon black soot is itself a nanoparticle.
Elimination of carbon black soot can theoretically be accomplished in many ways. One of those ways is to use advances in nanotechnology to create nonwovens capable of capturing such a particle at the source of its creation. Developments in imaging and measurement techniques have recently propelled the understanding of the morphology of soot and its impact. As more is learned about airborne particles and measurement systems advance to reveal more need for control, industrial nonwovens can meet the challenge.
H&V has an established position in nanofiber technology—ranging from glass to synthetic to composite materials—and has numerous nanotechnology-based products that are commercially available. Nanoweb for air and liquid filtration, our advanced nanofiber technology that offers submicron efficiency, low-pressure drop, and high performance against soot is available as a standalone web or a coating on nearly any substrate. IDEA 2013 award-winning NanoWave, the latest in H&V’s range of highly efficient HVAC filter media, offers the market a revolutionary design, ground-breaking dust-holding capacity, and long filter life.
Walker: How can the industrial nonwovens industry work together to advance the application of nanotechnology?
Ruiz: Questions around safety loom large. In order to enable the wide-scale adoption of nanomaterials in industrial nonwovens, the safety questions must be addressed. As stated earlier, nano scale materials generally show different properties than bulk scale materials. Since this difference is known, current assumptions about safety cannot be applied to these materials. The nonwovens industry can and should work together to evaluate various materials for their health impact and develop a set of standards for handling and use. Many nanomaterials show promise for utility, but remained underutilized as safety concerns continue to be unanswered.
Nanotechnology promises enormous opportunities for the industrial nonwovens industry, but there will be many challenges along the way. Keeping abreast of technology developments, new product developments, new applications, and health and safety issues will be key.
“TAPPI’s Nonwovens Division hosts an annual meeting, NET Inc., that regularly features the newest developments in nanotechnology applications to industrial nonwovens,” says Fatma SelcenKilinc-Balci, Senior Service Fellow with CDC, NIOSH, National Personal Protective Technology Lab in Pittsburgh, PA, and Chair of the Fibers, Materials & Characterization committee within TAPPI’s Nonwovens Division. “Due to the demand for more information on these newly developed nanofibers, nanomaterials and technologies to produce them, TAPPI will continue to host sessions featuring the latest developments in nanotechnology for industrial nonwovens.”
More information: www.tappi.org.