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A Hybrid Market

New developments in nonwovens are stemming more from evolution than from revolution.

Richard G. Mansfield, Technical Editor

A Hybrid Market New developments in nonwovens are stemming more from evolution than from revolution. New product research and development is the lifeblood of almost every business. However, there is no simple route to developing new products. With few exceptions, most new products result from evolution in technology rather than revolutions in technology. Many new products are developed by combining existing materials or processes to form a new product which is a hybrid. Hybridizing can then be considered as a process for developing new products. It can be considered that whole field of nonwoven technology as a hybrid, since nonwoven technology represents the combining of several basic technologies such as textiles, paper and polymers.

 Spunbond/Meltblown (SMS) ProductsKimberly-Clark has been the pioneer in combining meltblown nonwovens with spunbonds to develop a whole family of new products. The SMS products that have been developed by using a layer of meltblown polypropylene sandwiched between two layers of polypropylene spunbond are used for surgical wrap and for limited use in protective clothing and for automobile protective covers. Another development using combination technologies by Kimberly-Clark is their Coform system. This system creates a blend of meltblown polypropylene microfibers and powdered materials which is then formed onto a spunbonded carrier sheet.The semi-molten meltblown fibers, combined with the pulp and powdered materials, acts as a chemical-free adhesive system.The combination web formed by this process becomes a dimensionally stable, absorbent structure, even when it is wet. Thinsulate3Ms Thinsulate is used for apparel and footwear insulation. This product is made by incorporating a carded web of heavier denier crimped polyester fibers into a microdenier meltblown polypropylene web. The finer microdenier web provides the insulation properties and the carded web provides resilience for the composite structure. Water Blocking TapesThe swelling layer consists of a lightweight nonwoven coated with a chemically pure cellulose that is aerodynamically applied to become a super absorber. Super-absorbent fibers in the form of nonwovens produced by dry-laid processes are also used in this application. The backing layer is a polyester nonwoven such as a spunbond, or a dry-laid fabric reinforced with a polyester scrim.Many communications cables and fiber-optic cables contain a paraffin-like, highly viscous filling compound as a water-blocker in the cable core assembly. A swelling tape is applied to the filled cable core to seal off any cavities under laminated sheaths.To prevent the petroleum jelly from penetrating the nonwoven and impairing its swelling properties, polyester film is laid longitudinally over the cable core assembly and to wrap the swellable nonwoven around it in a second manufacturing step. Printed Circuit BoardsTo create a circuit board, a series of procedures must be followed. A circuit board is made by producing an isotopic aramid nonwoven, impregnating the nonwoven with the crosslinking resin system, drying the prepreg and obtain B stage crosslinkage, laminating it with copper foil in a roller laminator under clean room conditions, and then hardening the composite material for five hours at 120oC.A major advantage of this system is that the layers are bonded without using a solvent-containing adhesive. Battery SeparatorsComposite products have been developed for open systems of nickel-cadmium secondary cells. These cells are used in airplanes, rail vehicles and emergency generating sets. The electrolyte carriers used are polypropylene or polyamide nonwovens, combined with cellophane films or hydrophilic polypropylene membranes. Filtration ProductsCartridge filters can be formed by meltblowing or spray spinning techniques. Celanese Fiber Co. developed the Hytrex cartridge filters by using a spray spinning technique to produce a shaped cartridge filter of varying density. The Hytrex process and trademarks were sold to Osmonics Inc. which now markets these filter products. The Pall Corporation produces shaped cartridge filters by a modified meltblowing technique. Automotive ProductsThe application of polyethylene to jute carpet backed automotive carpeting to aid in its forming was an important development in the 1960s. Freudenberg Spunweb Co. has successfully introduced their Lutradur spunbonded polyester fabrics for moldable automotive carpeting.The high strength and ease of molding of the Lutradur permits the carpeting to have a deep draw configuration without encountering problems with punctures from high heels or similar hazards.Freudenberg in Germany developed a molded sound-absorbing automotive engine cover using polyester nonwoven fabric. Freudenbergs pleated polyester nonwovens are now used for air filtration media for car interiors.DuPont has done extensive work in developing moldable automotive and tractor seating fabrics that incorporated their Lycra® spandex to facilitate fabric molding. Molding Of FabricsCutting and sewing have been the traditional methods of joining and shaping textile fabrics into three-dimensional shapes.The felting of animal fibers into end items, such as hats, was one of the earliest methods of directly forming and molding fibers into a final product. Felts are also made in block form and other shapes by felting the wool or other animal fibers within a shaped form.Until thermoplastic fibers became available, it was not possible to directly form or shape fibers other than through felting. Garment MoldingGarment molding presents one of the most challenging areas for development of fabric molding technology. In the early 1970s, Teijin of Japan developed techniques for molding womens dresses using tubular double-knit polyester fabrics.With the increasing array of nonwoven fabrics now available, it is expected that molding and forming will continue to grow for specialty products such as automotive, filtration and other industrial products.The commercialization of limited use and disposable garments using molding technology for hospital/medical and clean room applications is also expected to increase.

August 1999