Research into how certain types of nonwovens technologies can incorporate electric currents when treated a certain way is quietly gaining ground in the industry. Both on the private level—from industry leaders like Kimberly-Clark and Hollingsworth & Vose—or within academia, i.e. NC State, these efforts have not yet made a big splash on the consumer market but researchers predict it won’t be long before nonwovens begin making a big name for themselves in electronics.
A desire to meet product requirements for a very low cost conductive materials in the personal care realm. This is what led Kimberly-Clark to start combining carbon fibers with paper making technology to develop products that add the benefit of heat in personal care items, such as wipes.
“As we filed the patents, we saw that it could go into many other applications beyond personal care—a heating cloth to treat pain, a heated wipe to improve its cleaning efficiency or even infusing a material with scent so it could acts as a scent-release vehicle, like a Plug-In,” said Michael Gross, senior associate for licencing at Kimberly-Clark.
Referred to by the company as cNonwovens technology, this technology has been under development for approximately five years and while the project that spurred this development is no long under review, Kimberly-Clark has been reporting a number of successes in attracting licensing interest for the technology.
While the process behind the technology is more similar to paper-making, K-C still considers it a nonwovens because of the process of how the carbon fibers are incorporated. The fiber widths range from 0.0002-0.0004 inches in diameter and the fiber length is 3 mm chopped.
Mr. Gross said there are several ways to go about production. The paper side, which is more developed, currently, involves adding the carbon fiber in the slurry and cutting the paper into a strip to form wires or slits to form a conductive pathways within the materials. However, if you want to get more of a nonwoven process, you can combine the carbon fibers during the melt blowing section of the Coform process. “If you do this, you have a Coform with meltblown and carbon fibers within the matrix,” he said. “This is where the strongest possibility of a heated wipe comes up. The wipe made of Coform is conductive. You can put a current in it by connecting a battery to the wipe substrate to warm it up.”
Potential applications for this technology could be a heated floor wipe, which makes sense because most people mop their floors already with hot water.
Another potential application is in RFID. By incorporating this technology into a simple dipole antenna or a scented tag, manufacturers can reap up to a 20% cost savings.
Currently, two dozen companies are evaluating the technology for smaller niche areas ranging from conductive clothing, with the ability to heat fabrics or even incorporate tracking devices, to disposable keyboards.
In short, K-C has been overwhelmed by the level of interest in the technology.
“We think this is a very promising technology and are looking to be able to license it in a number of different fields,” Mr. Gross continued.
Nothing New Here
Nonwovens’ role in electronics did not begin its story with K-C’s technology. Researchers have long been examining ways the flexibility and porosity of certain nonwovens technologies can work with printed electric circuits.
A couple of years ago, a group of NC State nonwovens researchers set out on a goal to print electric circuits onto conformed textile substrates under intelligent control. They did this by investigating the dispensing and printing of conductive transmission lines into a variety of nonwoven substrates using different fluids, such as conductive inks for durable and wearable electronic textile applications. Bonding methods included thermal bonding, solvent bonding, resin bonding, needlepunching and hydroentangled
Focused largely on the creation of wearable electronic textiles, challenges to this study largely centered on combining reliable and robust interconnect formation and improved signal integrity while maintaining textile characteristics such as lightweight, flexibility, strength, washability and weatherability. Meanwhile, the conductors had to be insulated to prevent shorts from occurring and the conductive fibers had to withstand handling such as washing and wrinkling. At the same time, the fibers had to be fine and elastic to be comfortable to the wearer.
Among the nonwovens being studied was Evolon, Freudenberg’s low-SVF spunbond/hydroentanbled structure, and Tyvek, a higher solvide volume fraction substrate.
Another pioneer in the field of electronics is Hollingsworth & Vose, a nonwovens producer that has long held a role in the battery separator market. In 2009, H&V launched Viamat, a nonwoven aramid paper which is used as a core substrate in printed circuit boards and flip chip carriers. Applications include avionics, medical devices, high capacity servers and other demanding uses.
Viamat’s advantages in circuit boards and chip carriers included low CTE for dimensional stability, an ultrasmooth surface, enhanced drillability, higher interconnect density and process capabilities. “ViaMat allows manufacturers to produce printed circuit boards with high interconnect densities,” Angelika Mayman, director of business development, said. “Small diameter vias and reduced spacing allow for increased capability on equivalent sized packages.”
While woven glass substrate have largely met market needs to date, they have inherent limitations with regard to via formation and dimensional stability. Films require substantially different manufacturing and handling capabilities and ViaMat can meet the increasing performance needs while being processed on existing assets.
According to Ms. Mayman, Viamat was born from H&V’s expertise in nonwovens technology based on aramid raw materials. “This expertise allows us to develop a material for printed circuit board applications and we intend to continue leveraging our capabilities into new markets. New products within the ViaMat family will focus on thinner caliper to meet the need for higher interconnect density boards.”
Electronic device makers favor the smaller sizes and lighter weights nonwovens can offer; at the same time nonwovens makers can value this market’s potential for growth and it acceptance of innovative, new products. Surely these factors will lead to more uses for nonwovens within the electronics market.
These efforts will surely open up new pathways for nonwovens. “People are continuing to look for ways to bring more value to consumers and differentiate from other products out there as nonwovens get more mature and it gets more difficult.”