Nonwoven fabric

Nonwoven fabricornon-woven fabricis afabric-like material made from staple fibre (short) and long fibres (continuous long), bonded together by chemical, mechanical, heat or solvent treatment. The term is used in thetextile manufacturing industryto denote fabrics, such asfelt,which are neitherwovennorknitted.Some non-woven materials lack sufficient strength unless densified or reinforced by a backing. In recent years, non-wovens have become an alternative topolyurethanefoam.

Multiple colored swatches of non-woven fabric

Applications

Because nonwoven fabrics do not require the intermediate step of converting fibres toyarn,they have more flexibility in materials usage. Nonwoven fabrics will commonly have a certain percentage of recycled fabrics and oil-based materials used in their construction, varying based upon the strength of material needed for the specific use. In addition, some nonwoven fabrics can be recycled after use, given the proper treatment and facilities. For this reason, some consider non-woven a more ecological fabric for certain applications, especially in fields and industries where disposable or single use products are important, such as hospitals, schools, nursing homes and luxury accommodations.

Nonwoven fabrics are engineered fabrics that may be single-use, have a limited life, or be very durable. Nonwoven fabrics provide specific functions such as absorbency, liquid repellence, resilience, stretch, softness, strength, flame retardancy, washability, cushioning, thermal insulation, acoustic insulation, filtration, use as a bacterial barrier and sterility. These properties are often combined to create fabrics suited for specific jobs, while achieving a good balance between product use-life and cost. They can mimic the appearance, texture and strength of a woven fabric and can be as bulky as the thickest paddings. In combination with other materials they provide a spectrum of products with diverse properties, and are used alone or as components of apparel, home furnishings, health care, engineering, industrial and consumer goods.

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

Medical

• isolation gowns
• surgical gowns
• surgical drapes and covers
• surgical masks
• surgical scrub suits
• caps
• medicalpackaging:porosity allows gas sterilization
• gloves
• shoe covers
• bath wipes
• wound dressings
• drug delivery
• plasters

Filters

• gasoline, oil and air – includingHEPAfiltration
• water, coffee, tea bags
• pharmaceutical industry
• mineral processing
• liquid cartridge and bag filters
• vacuum bags
• allergen membranes or laminates with non woven layers

Geotextiles

Main article:Geotextile

Nonwovengeotextilebags are much more robust than woven bags of the same thickness.

Geocomposite drain consisting of needle-punched nonwoven filter and carrier geotextiles ofpolypropylenestaple fibers each having a mass per area of 200 g/m².

Nonwoven geotextile containers (sand bags) are used for

• soil stabilizers and roadway underlayment
• foundation stabilizers
• erosion control
• canal construction
• drainage systems
• geomembraneprotection
• frost protection
• pond and canal water barriers
• sand infiltration barrier fordrainage tile
• landfill liners

They are more robust in handling as compared to their woven counterparts, and therefore were often preferred in large-scale erosion protection projects such as those atAmrumbank West;Narrow Neck, Queensland;Kliffende house onSyltisland, and theEider Barrage.In the last case, only 10 bags out of 48,000 were damaged despite a high installation rate of 700 bags per day.

Other

• diaperstock,feminine hygiene, and other absorbent materials
• carpetbacking, primary and secondary
• composites
  • marine sail laminates
  • tablecoverlaminates
  • chopped strand mat
• backing/stabilizer formachine embroidery
• packagingwhere porosity is needed
• Shopping bags
• insulation(fiberglassbatting)
• acoustic insulationfor appliances, automotive components, and wall-paneling
• pillows, cushions, mattress cores, andupholsterypadding
• battingin quilts or comforters
• consumer and medical face masks
• mailingenvelopes
• tarps,tenting and transportation (lumber, steel) wrapping
• disposable clothing (foot coverings, coveralls)
• weather resistanthouse wrap
• cleanroom wipes
• Labels
• potting material for plants
• Reusable shopping bag
• Thermal insulation
• Sorbents
• Surface protection
• wallcovering
• Wet wipe

Manufacturing processes

Main article:Melt blowing

Nonwovens are typically manufactured by putting small fibers together in the form of a sheet or web (similar topaperon apaper machine), 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 anadhesive,or thermally (by applyingbinder(in the form of powder, paste, orpolymermelt) and melting the binder onto the web by increasing temperature).

Staple nonwovens

Staple nonwovens are made in 4 steps. Fibers are first spun, cut to a few centimeters length, and put intobales.The staple fibers are then blended, "opened" in a multistep process, dispersed on aconveyor belt,and spread in a uniformwebby a wetlaid, airlaid, or carding/crosslapping process. Wetlaid operations typically use 0.25 to 0.75 in (0.64 to 1.91 cm) long fibers, but sometimes longer if the fiber is stiff or thick. Airlaid processing generally uses 0.5 to 4.0 in (1.3 to 10.2 cm) fibers. Carding operations typically use ~1.5 "(3.8 cm) long fibers.Rayonused to be a common fiber in nonwovens, now greatly replaced bypolyethylene terephthalate(PET) andpolypropylene.Fiberglass is wetlaid into mats for use in roofing and shingles. Synthetic fiber blends are wetlaid along withcellulosefor single-use fabrics. Staple nonwovens are bonded either thermally or by using resin. Bonding can be throughout the web by resin saturation or overall thermal bonding or in a distinct pattern via resin printing or thermal spot bonding. Conforming with staple fibers usually refers to a combination with melt blowing, often used in high-end textile insulations.

Melt-blown

Melt-blownnonwovens are produced by extruding melted polymer fibers through a spin net or die consisting of up to 40 holes per inch to form long thin fibers which are stretched and cooled by passing hot air over the fibers as they fall from the die. The resultant web is collected into rolls and subsequently converted to finished products. The extremely fine fibers (typically polypropylene) differ from other extrusions, particularly spun bond, in that they have low intrinsic strength but much smaller size offering key properties. Often melt blown is added to spun bond to form SM or SMS webs, which are strong and offer the intrinsic benefits of fine fibers such as fine filtration, low pressure drop as used in face masks or filters and physical benefits such as acoustic insulation as used in dishwashers. One of the largest users of SM and SMS materials is the disposable diaper and feminine care industry.

Spunbond nonwovens

Spunbond nonwovens 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, such as the REICOFIL machinery.PP spunbonds run faster and at lower temperatures than PET spunbonds, mostly due to the difference in melting points

Spunbond has been combined with melt-blown nonwovens, conforming them into a layered product called SMS (spun-melt-spun). Melt-blown nonwovens have extremely fine fiber diameters but are not strong fabrics. SMS fabrics, made completely from PP are water-repellent and fine enough to serve as disposable fabrics. Melt-blown is often used as filter media, being able to capture very fine particles. Spunbond is bonded by either resin or thermally. Regarding the bonding of Spunbond, Rieterhas launched a new generation of nonwovens calledSpunjet.

Spunlace nonwovens

Spunlace nonwovens are made by a process calledhydroentanglement.This process uses high-pressure jets of water to entangle fibers together, creating a strong, durable fabric. The process begins with a web of fibers, which can be natural or synthetic, laid out on a conveyor belt.

The web is then passed through a series of jets that spray water at high pressure onto the fibers. The water jets cause the fibers to tangle and interlock, forming a strong bond between them. The web is then dried and finished to create the desired product.

Flashspun

Main article:Flashspun

Flashspun fabrics are created by spraying a dissolved resin into a chamber, where the solvent evaporates.

Air-laid paper

Main article:Air-laid paper

Air-laidpaperis a textile-like material categorized as a nonwoven fabric made fromwood pulp.Unlike the normalpapermaking process,air-laid paper does not use water as the carrying medium for the fiber. Fibers are carried and formed to the structure of paper by air.

Other

Nonwovens can also start with films and fibrillate, serrate or vacuum-form them with patterned holes. Fiberglass nonwovens are of two basic types. Wet laid mat or "glass tissue" use wet-chopped, heavydenierfibers in the 6 to 20 micrometre diameter range. Flame attenuated mats or "batts" use discontinuous fine denier fibers in the 0.1 to 6 range. The latter is similar, though run at much higher temperatures, to melt-blown thermoplastic nonwovens. Wet laid mat is almost always wet resin bonded with a curtain coater, while batts are usually spray bonded with wet or dry resin. An unusual process produces polyethylene fibrils in aFreon-like fluid, forming them into a paper-like product and then calendering them to createTyvek.

Bonding

Both staple and spunlaid nonwovens would have no mechanical resistance in and of themselves, without the bonding step. Several methods can be used:

• thermal bonding
  • use of aheat sealer
  • using a large oven forcuring
  • calenderingthrough heated rollers (called spunbond when combined with spunlaid webs), calenders can be smooth faced for an overall bond or patterned for a softer, more tear resistant bond
• hydroentanglement:mechanical intertwining of fibers by water jets (also calledspunlace)
• ultrasonic pattern bonding: used in high-loft or fabric insulation/quilts/bedding
• needlepunching/needlefelting: mechanical intertwining of fibers by needles
• chemical bonding (wetlaid process): use of binders (such as latex emulsion or solution polymers) to chemically join the fibers. A more expensive route uses binder fibers or powders that soften and melt to hold other non-melting fibers together
  • one type of cotton staple nonwoven is treated with sodium hydroxide to shrink bond the mat, the caustic causes the cellulose-based fibers to curl and shrink around one another as the bonding technique
  • one unusual polyamide(Cerex) is self-bonded with gas-phase acid
• melt-blown: fiber is bonded as air attenuated fibers intertangle with themselves during simultaneous fiber and web formation.

Disposability

The industry has attempted to define "flushability".They encourage voluntary testing of flushability by producers. They also encourage clear marking of non-flushable products as" No Flush "(rather than fine print on the bottom of products) including creating a" No Flush "logo.

Thewastewater industryis encouraging a standard definition (rather than one which varies with each producer) of flushability, includingdispersibility,and third-party assessment or verification, such as byNSF International.They believe that products should be safe for both septicandsewer systems (flushable and dispersible, respectively).Orange County Sanitation Districthas created a campaign, "What 2 Flush", which recommends flushing only the "three P's—pee, poop and [toilet] paper".

See also

• Disposable towel

External links

• Association of Nonwovens(EDANA: Europe)
• The Association of the Nonwovens Fabrics Industry(INDA: US)