Nonwovens are fiber-based products that are formed into mats of randomly-oriented fibers, felt, needlepunched cloth, spunbond, or meltblown structures. They differ in terms of form, materials, dimensions, properties, features, and applications. Nonwoven fabrics are neither woven nor knitted. Instead, these textiles are produced by grouping by grouping fibers into a sheet and binding them with an adhesive or interlocking them with serrated needles. Traditional nonwovens are not suitable for stretching; however, the strength of nonwoven fabrics can be increased by adding a backing. Today, nonwovens are often used in products such as filters, webs, mats and batts.
Types of Nonwovens
There are three basic types of nonwovens: wet-laid or air-laid, spunbond or meltblown, and carded or needlepunched. Wet-laid nonwovens and air-laid nonwovens are made from short-cut fibers. They offer highly uniform structures with controlled porosity and smooth surfaces. Spunbond nonwovens and meltblown nonwovens are made from continuous, extruded fibers. They are relatively inexpensive when compared to other nonwoven products. Spunbond nonwovens and meltblown nonwovens also have high strength in the machine direction. In addition, many provide very-high absorbency. Carded and needlepunched nonwovens offer very high loft (low density) at a very low cost.
Nonwovens are made from a variety of natural, synthetic or polymeric, ceramic, and metallic materials. Natural fibers are made of cotton, jute, leather, linen, flax, silk, or wool. Synthetic fibers are made of acetate, triacetate, acrylic, modacrylic, aramid, elastomer, fluropolymer, nylon, polyamide, olefin, and polyolefin fibers. Nonwovens made from polyester, polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), and styrene acrylonitrile (SAN) are also available. Ceramic nonwovens include filters, webbing, matting, and batting made from alumina or silica carbide (SiC). Material systems for nonwovens also include boron, carbon, E-glass, S-glass, rock wool, slag wool, glass, and fiberglass. Nonwovens with metal fibers have a shiny surface, high density, ductility, high melting point, high hardness, and high thermal and electrical conductivity.
Selecting nonwovens requires an analysis of dimensions, properties, performance features, and structural features. Fiber denier, fabric weight, overall thickness, overall width, and overall length are important dimensions to consider. Properties for nonwovens include use-temperature, fabric strength, breaking strength or load, thermal conductivity, and electrical resistivity. In terms of performance features, some nonwovens are flame-retardant, chemical or fuel resistant, cut resistant or bulletproof, weather or UV resistant, hydrophilic or absorbent, hydrophobic or waterproof, and UL approved or UL listed. Other nonwovens provide structural features such as thermal bonds, micro fibers, blended fiber structures, copolymer or bi-components, chemical bonds or binder additions, hydro-entanglement, and coating or sizing.