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Nonwovens / Technical Textiles

Nonwovens Enhance Car Performance

Enhanced sound absorption, reduced weight for improved fuel economy are among the benefits offered by automotive nonwovens.

Jürg Rupp, Executive Editor

F or years, textiles enjoyed steady growth, but in the second half of 2008, in line with the world financial turmoil, automotive sales dropped drastically, and automotive textile sales declined as well. However, automotive nonwovens are high-tech products that offer some astonishing performances, especially for improving sound absorption and fuel economy.

Rieter Automotive Systems, a member of the Switzerland-based Rieter Group, reported the automotive component supply industry saw production volumes drop steeply. However, in the second half of 2008, the company began initial production of aerodynamic underfloor modules incorporating lightweight Rieter Ultra Silent fiber technology, which helps vehicles achieve significant reductions in carbon dioxide emissions.

  car door panel

Needlepunched nonwoven fabrics may be stiffened with
resins and molded to form automotive interior parts.

Evolon ® Microfilament Fabric
Evolon ®, produced by France-based Freudenberg Evolon S.a.r.l., is produced by spinning mainly 16-segment pie continuous filaments primarily of a polyester/nylon 6 blend, split and consolidated to isotropic fabrics weighing between 40 and 240 grams per square meter (g/m 2) with final counts from 0.05 to 0.2 decitex (dtex). The process allows in-line reinforcement with air-permeable layers.
A 16-segment pie, 0.15-dtex product weighing only 100g/m 2 shows air flow resistance between 800 and 1000 Rayls - the range considered best for sound absorption. As this range has to be respected also for multiple-layer fabrics, Evolon is adapted by lower weight to the requirements of the final composite. Further fine-tuning to customers' requirements - including flame retardation, water repellency, direct lamination preparation, and thermoformability - is possible during production. One can find Evolon for sound absorption incorporated in mats and carpets, and within the dashboard.

Doors, bumpers and other parts ready for assembly have been transported in bags hanging on metal racks. These bags were first disposables, which increasingly are being replaced by durables. Microfilament-based Evolon satisfies nonabrasive, pilling-resistant, abrasion-resistant, water-repellent, easy-to-convert and durable-to-water-jet-cleaning requirements for these bags, according to Freudenberg Evolon. As the product is lint-free and filters the finest particles, it is even used between painting steps for transporting during manufacturing. On top of that, Evolon facilitates production logistics. For heavy transporting, the product is reinforced by single coarse filaments, coarse-denier layers of nonwoven or scrims. One could even transport complete cars in these bags.

In Japan, and coming to Europe, Evolon is being used in car wash installations. The fabric offers a combination of microfilament cleaning and nonabrasive properties, durability, and pilling and abrasion resistance.

Lightweight Constructions
The automotive industry's current economic difficulties will be a driving factor to further develop lightweight, low-cost needlefelt floor systems for cars, reports Germany-based needle loom manufacturer Dilo Group. At the same time, the threat of global warming dictates the need for fuel-efficiency, creating a preference for small and mid-sized, lighter-weight cars over larger, heavier vehicles.

In Asia, needlefelt constructions used as molded floor parts have a large market share, but less so in Europe. In the United States, there is a potential to use needlefelt formed parts for such applications. Inexpensive needlefelts may enable further weight reductions compared to other constructions. In addition, they have a superior resistance to liquid stains.

Needlefelts seem to have low wear resistance and are hard to clean of debris such as dog hair or pine needles. Needled lightweight mats that can easily be replaced when worn out or dirty could address these issues.

Further weight reductions can be designed into a lightweight car interior floor covering construction. For flat or random velour constructions, the staple-fiber web-forming process should be evaluated for further possible improvements.

For good moldability and minimum weight, a highly regular weight distribution and preferably a random fiber orientation in the web is needed. The molding process stresses the fibrous mass differently across the plane, as the degree and direction of stretch varies. Therefore, a homogenous mat might be a good prerequisite to better provide just enough material to sustain the stressed areas.

Fiber Preparation And Web-Forming
Forming and production of such homogenous webs requires a high blending quality using homogenous blends, especially when low amounts of costly low-melt or bicomponent fibers are used. Dilo Temafa offers systems such as Baltromix in combination with Mixmaster for blending operations.

When dosing the flocks in machine direction (MD) and cross direction (CD) of the card, a fine opening station may be used; card feeders today offer much improved weight profiles. Installing Dilo Spinnbau's Delta transfer system between the breast and main section of a card can improve the card's blending function, the company reports. Additional randomizer rollers at the doffing section may provide a good pre-orientation of the web when increased MD strength is intended after crosslapping.

If an even cross profile in the mass distribution of the crosslaid batt is specified, Dilo offers Profiline CV1 to control the weight across the layering width within close tolerances. The MD weight profile of the crosslaid batt is controlled by a high layering precision with close lapper joints. Even with random rollers on the card, further controlled drafting for the batt and the pre-needled felt is recommended.

  Automotive pic1

Evolon® nonwovens, when used in car wash installations,
offer microfilament cleaning and nonabrasive properties,
durability, and pilling and abrasion resistance.

Drafting And Needling
A complete Dilo needling line includes three process steps that may correct the predominantly cross-directional fiber orientation after the crosslapper, and produce felts that have an isotropic strength MD:CD ratio of about 1:1. To eliminate increased weight variations caused by uncontrolled drafting, a lap drafter provides numerous small drafting zones instead of having two distant rollers between which there is less drafting control.

Within the needling zone, it is important to have a controlled feed through a compressive batt feeder. At the same time, Dilo reports, a Hyperpunch mode with two-dimensional elliptical needling provides advantages, particularly during pre-needling. During the felt drafting stage, very close settings with a minimum drafting zone length can maintain batt regularity to a large degree. At the finish needling stage, elliptical needling enables high throughput speeds as well as low dimensional changes, MD draft and CD shrinkage.

Random Velours
After pre-needling, Dilo's DI-LOUR process can convert the surface into velour by needling the material into a brush moving in machine direction, providing very small dimensional changes while keeping a very consistent weight distribution. Dilo offers the technology in two versions: DI-LOUR II single structuring and DI-LOUR IV double structuring.

In double structuring, pile density and stability are increased. The range of patterns also can be expanded using a two-colored web and advance patterning, which enables a variety of cross-line diagonals, MD lines, fine dot patterns and other patterns. A second layer fed on top of the first prestructured layer can contain different fibers, including low-melt, bicomponent or recycled fibers. The two-layered product thus produced offers a wide range of features to serve various purposes such as improved aesthetics and quality, moldability and other features.

May/June 2009