Nonwovens: Protecting Against NOISE

By Karen McIntyre, Editor | April 12, 2010

offering the same or better performance at lower weights, nonwovens are becoming the favored acoustical medium in a number of markets

In markets like automotives and home construction, where market growth has been dour in recent months, one bright spot, for nonwovens at least, has been in the acoustics market. Here, nonwovens are replacing shoddy materials to offer similar performance at lower weights and less materials, saving money and lowering space requirements.

Entry into the acoustics market, in fact, is offering nonwovens producers several benefits. For one, acoustic performance is something customers are willing to pay for; for another the acoustics market is looking for cost effective, recyclable, lightweight and flexible products, traits all achievable by nonwovens.

While the acoustics market continues to be niche for nonwovens producers, those involved in the market are reporting success across a number of product platforms, notably automotives, construction and the home appliance market. In these markets, nonwovens producers can grow marketshare through value-added innovations without being victim to the pricing pressures and competitive climate felt in other nonwovens markets.

“Acoustical nonwovens are a growth market,” said Kristina Müller, spokeswoman for nonwovens producer Sandler. “Owing to their versatility, they continue to open up new areas of application where they demonstrate their flexibility and functionality. Given this continuing growth and exploitation of new domains, acoustical nonwovens will not remain a niche market.”

Already, Sandler nonwovens are found in more than 40 automotive models and the company is focusing on specific new developments in this business area which, in the long term, will certainly result in a positive trend.

Of course, this success is not without its challenges. Many of the markets targeted by acoustic nonwovens have been impacted by the economic downturn and while they are looking for the high performance benefits and cost effectiveness of nonwovens to help them edge out the competition, unit sales continue to be lower than they were a few years ago. For instance, in automotives, while more acoustics are going into each vehicle than ever before, at the same time, manufacturers are selling fewer cars.

Cool For Cars

Still, it seems cars are where most of the action is today when it comes to acoustical nonwovens.
From the inside of the trunk to the cab interior to the engine and wheel wells, auto manufacturers are looking to create a new soundless environment within the car. With smaller cars being more favored by many—owing to higher gas prices and other economic concerns—acoustics are more important than ever. Smaller cars tend to “ride rougher” than larger cars, but manufacturers want to create the same sense of luxury in more later models.

“The automobile is no longer just a means of transportation, but a living space, a vehicle of experience, a place of relaxation,” said Ms. Müller. “Acoustics have particularly become of paramount importance. Motor and road noise need to be absorbed where they emerge in order to allow for a good communication between the occupants in the passenger compartment. OEMs are still looking for lightweight, temperature stable, recyclable materials with excellent technical data and low emission rates at the same time.”

Another obvious trend for automotive acoustic components in North America is the development of lightweight products that answer a call from OEMs looking to meet recent CAFE (Corporate Average Fuel Economy) requirements. Created by the National Highway Traffic Safety Administration (NHTSA), CAFE standards were designed to regulate the sales weighted average fuel economy of passenger cars or light trucks manufactured for sale in the U.S. for any given model year. Here nonwovens play a key role because they can be designed to be lightweight and can therefore help vehicles meet higher fuel efficiency levels.

Nonwovens are able to meet all these needs thanks to their versatility. The multitude of production technologies offers a wide variety of possibilities to adapt the material to specific customer needs. Not only can nonwovens contribute to the lightweight construction of the automobile but they can simultaneously retain excellent sound and heat insulation properties. Their resistance to various fluids as well as germs and fungus makes synthetic nonwovens made of polyester, for example, ideal materials for exterior applications in the automobile as well as for insulation in the construction industry.

As nonwovens continue to expand their role in the automotives market, they are also being called upon to fulfil requirements beyond minimizing noise. For example, in the acoustic materials in the trunk of the car need to look a certain way even though they exist underneath the carpet. “They want these materials to look nice even though they’re largely out of view,” said Peter Hartwig, managing director of J.H. Ziegler. “This is beyond the general requirements of lighter weights and lower emissions.”

Additional requirements include fire proofing—within the engine area of the car—oleophobicity and hydrophobicity and the ability to offer color. “It all really depends on where the material is being placed in the car,” Mr. Hartwig added.

Still, the greatest requirement of acoustics in automotives, and a big part of the reason why nonwovens have succeeded in this market, is their ability to offer the same or better performance as competing materials at lower weights. This is largely achieved through the use of fine fibers—molded through either a thermal bonded or needlepunched process—and as less and less space is constantly being devoted to the acoustics portion of the car, research efforts are underway to create even more effective materials.

Two companies leading the way in this area are Elmarco and Oerlikon Neumag, who have forged a partnership to develop lines, processes and products based on nanofiber technology. The combination of Elmarco’s nanofiber know-how and Oerlikon Neumag’s nonwoven technology, allowing the companies to offer complete technological solutions for nanofiber applications such as Nanospider AcousticWeb sound absorbent materials.

Elmarco developed electrospinning methods to produce very fine nanofibers and had already partnered with spunmelt nonwovens producer Avgol to develop filtration media using the technology. In spunbond applications, Elmarco’s principal needs to be incorporated offline because of production speeds. The spunbond is produced, wound and then the nanofiber is placed on it. Conversely, when it came to carding, the nanofiber technology had to be done online because of the bonding step. Oerlikon was a good match for Elmarco in developing this technology because it could offer a three-layer doffing line; a layer of nanofibers was placed between the carding layers, making five layers total.

Oerlikon’s Stefan Schlichter said this five-layer structure was perfect for acoustical applications because it can achieve a superior dampening effect and better frequency at low volumes and less weights than competing materials. “The mat has to be much thicker and you can achieve this with the combination of layers to make a return on your investment. The second benefit is it will fit into some applications where you have a limited requirement for weights or dimensions, for example in dishwashers. There is a need for dishwashers to run more quietly, but their design is standardized so you can only add so much acoustical materials.”

Also focusing on lightweight acoustic nonwovens for automotives is eswegee Vliestoffe. The German company has been active in the segment for more than three years and has recently placed its Zetajet spunlace nonwovens in a number of vehicles where they are used in acoustic applications such as hoodliners, dash inner and outer, tunnel insulation, firewall, underbody shields, headliners and infection molding, according to Detlev Kappel, technical nonwovens director.

“Due to enormous cost pressure from OEMs for improved acoustics and lighter weights in the car, we developed a new product range of lightweight nonwovens to comply with these new ideas,” he said.

Meanwhile, 3M Acoustics Solutions are offering low-density products to meet even stricter performance and weight requirements. Its expanded range of Thinsulate acoustic insulation includes low density products that focus on mass reduction and high performance.

The Green Factor

Environmental considerations abound within the acoustics market as manufacturers look to make their cars, appliances, buildings, etc. more environmentally responsible. Whether it’s a lighter weight acoustic making a car more fuel efficient or acoustical insulation making a building safer and with more attractive sound levels and the ability to make a material either from post consumer waste or with the ability to be recycled, manufacturers are touting the green benefits nonwovens can offer.

In Europe, this is particularly important as starting in 2015, End-of-Life vehicle regulations will require that at least 95% of the weight of all car components must be recyclable. This requires unmixed raw materials which will be an advantage for nonwovens suppliers whose products are based on a single polymer.

Other factors include demands for clean processing and low emission materials and end products.

“The issue of producing ‘green’ products is becoming more and more important, as nonwoven acoustical components account for a high percentage of the material used in a car,” said Miss Müller. “Producers demand materials which can be processed cleanly and have a low emission level. Moreover, from 2015 onwards at least 9 % of the weight of all the components of a car will have to be recyclable. This requires unmixed raw materials. Sandler’s nonwovens for the automotive industry are made of a single polymer material (100% PET) and can therefore be integrated into a cycle of reusable materials. Moreover, with our lightweight products we develop and produce according to our motto “less is best for nature.” Due to the low weight of our polyester nonwovens, less material, which has to be recycled, is processed in an automobile. Moreover, the lower weight also contributes to reducing the fuel consumption.”

Meanwhile, 3M Acoustic Solutions’ efforts to reduce its carbon footprint have included lowering volatile content through partnerships with OEMs. One example could be using non-petroleum-based natural materials, but determining which material is best to be used could pose a challenge. “The real challenge in going green is not necessarily cost but finding a common definition,” said Bronwen Kleissler, portfolio manager for 3M Acoustic Solutions.

“There’s an opportunity in our industry right now to write all of the definitions of green.”
A further challenge, of course, could be choice, and in today’s competitive marketplace manufacturers may not be willing to pay for a more ecofriendly benefit if it does not translate to higher price tags in the marketplace.

Anytime, Anyplace

Canadian needlepunch maker Texel has seen some great success with its ThermoFit product, which is available in synthetic, natural and composite version and can be engineered to unique customer specifications. Automotive applications include exterior wheel well liners, storage compartment such as the glove compartment and truck storage bins, door panels, package trays and dash inserts as well as other areas including furniture panels and door panels.
“Anything and everything a nonwovens company is doing in acoustics to minimize noise is getting evaluated,” said Gale Shipley, sales manager for automotive. “These products can offer two-fold benefits—blocking out noise and offering privacy.”

For example, acoustical nonwoven are finding use in office panels, forming a sound barrier between one cubicle and another, or in home theaters, recording studios or other rooms that require sound not to dissipate to other parts of the home.

“There is a genuine interest in acoustics,” Ms. Shipley said.

“With the ever increasing population and loss of space, everyone is sensitive to noise these days.”

Back in the automotive segment, Texel is exploring the development of a product to replace foam in some of the thinner foamed areas of the vehicle like headliners. Many vehicles have a three millimeter foam layer behind the face fabric. This product will eliminate the foam that is known to contain some hazardous components with something that is more recyclable and environment friendly.

Sandler is also seeing entry into new markets for its acoustical products, particularly in insulation products for roof and wall construction. Acoustical insulation combines the benefits of contributing to both the noise level and temperature regulations. Executives expect to see growth into new markets as well thanks to the versatility of nonwoven materials.

“Nonwoven materials are very versatile and continue to tap into new markets and new applications, constantly replacing previously used materials. In the nonwovens industry, innovation is not only to substitute common materials with technical textile solutions; nonwovens also permit the exploitation of new fields of application,” said Sandler’s Ms. Muller.  “Nonwoven materials are lighter, more versatile in their functionality and the production and processing is cleaner.”