The Smaller, The Better

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small fibers mean big business for nonwovens in filtration, medical, apparel, home furnishing & industrial uses

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By Ellen Wuagneux
rnAssociate Editor

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rnJust how small is a microfiber? This depends on how you define it, but according to most industry experts, a microfiber is smaller than most fibers used for nonwovens but not nearly as small as a nanofiber. Conventional nonwovens have fibers with diameters ranging from one to 100 microns. Nanofibers produced by various processes will have diameters in the range of several nanometers up to 1000 nanometers. A micron, or micrometer, equals 1000 nanometers.
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rnVarious process technologies are used to produce microfiber nonwovens for applications requiring barrier properties and high surface areas, including specialty meltblowing, electrospinning, electroblowing and splittable fiber approaches. While microfibers are well established in meltblown and wetlaid microglass technologies, the next frontier is expected to involve fibers with even smaller diameters—or nanofibers.
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rnThe benefits of microfibers are many. They allow roll goods producers to manufacture lightweight, strong fabrics with excellent breathability, moisture wicking, fabric drape and opaque performance attributes. Their limitations are more associated with cost-performance requirements and the number of capable producers than with the microfiber nonwovens themselves. Thanks to increased performance attributes, microfiber nonwovens are being used increasingly to replace traditional woven fabrics, although they don’t necessarily come at a lower price.
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rnIn filtration, micro and nano fibers are used to trap increasingly fine particles while maintaining a fabric’s high flow rate. Despite their functional benefits, they fall short when it comes to ease of handling during the manufacturing process. Although it is one of the oldest nonwovens technologies, the wetlaid process actually offers the flexibility needed to produce media containing microfibers.
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rnOne recent example of a technology making use of the wetlaid process to produce microfiber nonwovens is Ahlstrom’s Disruptor technology, which uses microglass and nanoalumina fibers. Winner of the INDEX 08 award, Disruptor nanofiber-based filter media combine two mechanisms—electrokinetics and mechanical entrapment. Its main features include low pressure drop, high loading capacity and superior filtration efficiency.
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rnOther major uses for microfibers in nonwoven applications include home furnishing, industrial and medical fabrics. In the area of apparel, where there is high interest in textile quality microfiber-based nonwovens, a key limitation has been their inability to achieve appropriate fabric hand, drape and aesthetic properties.