Non-woven textiles are those which are neither woven nor knit, for example felt. Non-wovens are typically not strong (unless reinforced by a backing or densified). In the recent years non-woven material has become an alternative to polyurethane foam.

Non-woven fabric is manufactured by putting small fibers together in the form of a sheet(web) and then binding them either mechanically (as in the case of felt, by interlocking them with serrated needles such that the inter-fiber friction results in a stronger fabric), with an adhesive, or thermally (by applying binder(in the form of powder, paste, or polymer melt) and melting the binder onto the web by increasing temperature).

Raw material

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Non-woven materials are nowadays mainly produced from man-made fibers. Two synthetic polymers dominate the market: polypropylene and polyesters (mainly PET). Nonwovens are often application-designated as either durable or disposable. Nonwoven used as a housewrap to prevent water infiltration is a durable nonwoven. Nowoven used as a facing on a baby diaper is a dispoable or single-use nonwoven.

Applications

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Non-woven materials are used in numerous applications, including:

• Hygiene
  • Baby diapers
  • Feminine hygiene
  • Adult incontinence products
• Wipes
  • Domestic
  • Technical
• Filters
• Geotextiles
• Carpet backing
• Composites
• Backing/Stabilizer for machine embroidery
• Insulation (fiberglass batting)
• Pillows, Cushions, and upholstery padding
• Batting in quilts or comforters
• Consumer face masks
• Disposable clothing (Surgical Scrubs, Mask, Cap, Foot Covering, Coverall)

Manufacturing processes

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Staple non-wovens

Staple non-wovens are made in two steps. Fibers are first spun, cut to a few centimeters length, and put into bales. These bales are then dispersed on a conveyor belt, and the fibers are spread in a uniform web by a wetlaid process or by carding. Wetlaid operations typically use 1/4" to 3/4" long fibers, but sometimes longer if the fiber is stiff or thick. Carding operations typically use ~1.5" long fibers. Rayon used to be a common fiber in nonwovens, now greatly replaced by PET and PP. Fiberglass is wetlaid into mats for use in roofing and shingles. Synthetic fiber blends are wetlaid along with cellulose for single-use fabrics.

Spunlaid non-wovens

Spunlaid non-wovens are made in one continuous process. Fibers are spun and then directly dispersed into a web by deflectors or can be directed with air streams. This technique leads to faster belt speeds, and cheaper costs. Several variants of this concept are available, but the leading technology is the Reicofil machinery, manufactured by Reifenhaüser (Germany). PP spunbonds run faster and at lower temperatures than PET spunbonds, mostly due to the difference in melting points. Spunbond has been combined with meltblown nonwovens, coforming them into a layered product called SMS (spun-melt-spun). Meltblown nonwovens have extremely fine fiber diameters but are not strong fabrics. SMS fabrics, made completely from PP are waterproof and fine enough to serve as disposable fabrics. Meltblown is often used as filter media, being able to capture very fine particles.

Bonding

Both staple and spunlaid non-wovens would have no mechanical resistance "per se" without the bonding step. Several methods can be used:

• thermal bonding
  • using a large oven for curing
  • calendering through heated rollers (called spunbond when combined with spunlaid)
• hydro-entanglement: mechanical intertwining of fibers by water jets (called spunlace)
• needlefelt: mechanical intertwining of fibers by needles
• chemical bonding (wetlaid process): use of binders (such as latex polymers) to chemically join the fibers or a more expensive route is to use binder fibers or powders that will soften and melt to hold other non-melting fibers together

Textiles

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