Advancing Needlepunched Nonwovens
Needlepunched nonwoven fabric growth is fueled by advanced technology.
Richard G. Mansfield, Technical Editor
Needlepunched nonwovens are produced by mechanically interlocking the fibers of a carded, airlaid or spunbonded web using a needle-loom. Early needlelooms operated at relatively low speeds of up to 100 strokes per minute. Jute, sisal and animal hair were the major fiber materials used in the early needlefelts for carpet underlay and spring insulators for furniture and mattresses. Needling requirements for making papermaker felts for the papermaking industry drove the need for higher speeds and greater precision in needlelooms.
John Foster, vice president, Foster Needle Co. Inc., Manitowoc, Wis., has provided the following description of the basic types of needlelooms:
The most commonly built needleloom in the world is the singledown punch machine. This basically consists of one single needle board going across the entire length of the machine. The single board machine does a good job needlepunching those products that do not require a high degree of integrity of strength — such as paddings and waddings, carpet pads, etc. For more intense needlepunching, the needleloom producers will add needle boards to their machines. This machine is a double board up and down punch. In other words, the needleloom has four boards, two of the boards needle from the top and two needle from the bottom. So for lower intensity needle-punching, single board needle-looms are commonly used, and by adding more needle boards to the needlelooms, they are better suited to produce products that require higher needle penetration levels. The degree of needle penetrations is measured as needle penetrations per square inch (ppsi). Since ppsi is related to throughput speeds, this variable is important.
PPSI plays an important role with such product characteristics as tensile strength, surface characteristics, porosity and much more. Up to a certain point, [the higher the fabric’s ppsi, the higher its strength]. Beyond this point, higher ppsi will lower fabric strength because of fiber breakage.
Listed below is the general range of ppsi needed to produce various types of needlepunched products:
• man-made leather substrates: 5,000 ppsi;
• geotextile — 4 ounces per square yard (oz/yd2): 1,500 ppsi;
• filter media — 12 oz/yd2: 1,200 ppsi;
• blankets — 10 oz/yd2: 800 ppsi; and
• carpet cushion — 30 oz/yd2: 200 ppsi.
The elliptical needling process of the Dilo DI-LOOM HSC Hyperpunch provides increased productivity and improved surface appearance, according to Dilo Systems Group.
In addition to the formation of alliances, there have been acquisitions such as the Switzerland-based Saurer Group’s acquisition of Fehrer via its Neumag nonwovens machinery subsidiary (See “ Nonwovens/Technical Textiles News,” TW, July/August 2005), which previously had acquired North Adams, Mass.-based needleloom producer Morrison Berkshire’s intellectual property rights for the design and manufacture of paper machine clothing web-forming, needling and finishing machinery; and Switzerland-based Rieter Textile System’s recent cooperation agreement with NSC.
NSC’s development of the A.50-SDB needleloom is designed to rib a heavy carpet product at speeds of up to 16 meters per minute, which corresponds to 1,250 kilograms per hour.
Major suppliers of needles for needlelooms, such as Foster Needle and Groz-Beckert USA Inc., Fort Mill, S.C., are keeping pace with machinery developments. They are supplying needles that are more resistant to breakage and have a longer wear life, as well as finer needles.
These developments enable structured needlepunch fabrics to be used in interior trim and floor coverings for automotive, recreational and boating products. Needlefelts’ market share in filtration is increasing. Improvements in control systems for needlepunching lines simplify product changeovers and improve quality control.
The increase in productivity is resulting in overcapacity in larger commodity-type fabrics for geotextiles, hospital/medical, furniture and apparel applications. Product development efforts have accelerated to find more profitable niche specialty markets for needlepunch fabrics.
Dr. Ernst Fehrer AG's NL 11/Twin-SE Carpet-Star is one example of structured needlelooms that enable production of an increased range of rib and velour patterns.
“Needlefelts provide a simple process for controlled fiber orientation. [T]he felting process mechanically moves fibers into the Z direction to ensure strength,” the company reports.
Needlefelt properties include:
• controlled fiber orientation in the machine or cross-machine direction, or at an intermediate angle;
• Z-directional strength, which improves shear strength and reduces the potential for ply delamination;
• high void volumes for easy absorption of resins;
• cost-effective thickness of composite structures by reducing the number of plies, weight, lay-up times and overall costs;
• ease of blending diverse fibers and fiber structures such as high-strength and thermoplastic fibers during the needlepunching process;
• distinct batt layering of two or more layers of distinct fiber types in one needlefelt, and the ability to incorporate lightweight woven fabrics, films and other fabric forms into the needlefelt structure; and
• compressibility for easy molding or shaping, which allows for intricate design.
Tex-Tech has used its experience in products for the commercial aviation industry to develop fire-blocking products for school bus, railroad and racing car seating. Its patented fire-blocking fabric is a nonwoven needlepunched fabric layer preferably saturated with a treatment as a means for imparting water and stain repellency to the fabric. The surface treatment consists of a fluoropolymer, such as Wilmington, Del.-based DuPont’s Zonyl™ or St. Paul, Minn.-based 3M’s Scotchgard™. This treatment is applied using a conventional textile padding process, and is subsequently dried and cured.
PCC also produces a hot-melt coated needlepunched fabric laminated to a spunlaced nonwoven used in Princeton, N.J.-based Church & Dwight Co. Inc.’s Brillo Scrub ‘n’ Toss® scrubbing pads. The scrubbing action of the pad results from the proper selection of a lower-melt fiber blend component and the hot-melt coating.
The company’s patented process is used to form fibrous preform structures such as carbon or graphite products suitable for subsequent processing into high-temperature-resistant composite structures such as aircraft brake discs.
The process compensates for fiber pullback induced by fiber resilience, and for compaction in previously needled layers induced during subsequent needle passes. The displaced fibers generated by the needling process are referred to as Z-fibers because they are generally perpendicular to the layers comprising a fibrous preform structure. Z-fiber distribution throughout the thickness of the fibrous preform structure may be manipulated as necessary to achieve a desired distribution. Z-fiber distribution throughout a brake disc can have a profound effect on disc wear life and on performance of the brake disc in slowing or stopping an aircraft.
The blanket is made of a needlepunched webbing of pre-oxidized polyacrylonitrile fibers. The fabric then is assembled using carbon precursor fibers that have been interlocked using a needlepunch process to produce a nonwoven and non-plush fabric. The resulting weld blanket is light-weight and effective at a cost-effective thickness and density.
In use, the weld blanket can be taped to automobile components or industrial equipment to ensure the security and protection of equipment from molten spatter near welding locations.