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Nonwovens

One of the oldest nonwoven fabrics is felt.  Felt is either 100% wool fibres, or a blend containing wool fibres (Fig. 1).  These fibres are then treated with heat, moisture and then agitated. In 1930’s and 1940’s synthetic polymers, with thermoplastic properties, were developed and introduced on to the market (Fig.2).  Freudenberg ( a major player in the nonwovens market to this day) began trading in 1938 and went into production artificial leather for World War Two.  The main nonwoven process technologies were developed between 1940 and 1965, and this can be seen as the start of the nonwovens industry that we know today.

 

Fig 1

Figure 1 Wool and hair fibres, due to their unique surface scales, are the only fibres with the ability to felt

Fig 2

Figure 2 Wallace H Carothers DuPont, 1896-1937 Neoprene, PA (Nylon), PET (Polyester)

 

 

 

Defining of  nonwovens

Woven and knitted fabrics require a preliminary set of spinning yarns from fibres before fabric assembly.  In some nonwoven manufacture the fibres are assembled directly into fabrics (missing out the yarn stage), and in other nonwoven manufacture the fabric is made directly from the polymer (i.e. the material goes from polymers to form a stable fabric in a single processing step).

As the term  nonwovens covers a large variety of differing manufacturing processes the definition of a nonwoven is not a simple one.

Definition ISO 9092:1988 & EDANA

“A nonwoven is a sheet of fibres, continuous filaments, or chopped yarns of any nature or origin, that have been formed into a web by any means, and bonded together by any means, with the exception of weaving or knitting.

Felts obtained by wet milling are not nonwovens.

Wetlaid webs are nonwovens provided they contain a minimum of 50% of man-made fibres or other fibres of non vegetable origin with a length to diameter ratio equals or superior to 300, or a minimum of 30% of man-made fibres with a length to diameter ratio equals or superior to 600, and a maximum apparent density of 0.40 g/cm³.

Composite structures are considered nonwovens provided their mass is constituted of at least 50% of nonwoven as per to the above definitions, or if the nonwoven component plays a prevalent role.”

More information on the definition of a nonwoven can be found on the EDANA and INDA websites

Nonwoven associations

INDA Founded in 1968, INDA is the leading global nonwovens association. INDA member companies represent the entire nonwovens value-chain. 

EDANA:  Formed in 1971 originally as the European Disposables and Nonwovens Association, for more than three decades EDANA has grown and evolved, to become today a modern industry association with a European focus and global influence and profile, reflecting the changing dynamics of the nonwovens industry. 

“Standard Test Methods for the Nonwovens Industry” was published in April 2005, the result of a joint effort of EDANA and its North American counterpart INDA.

Nonwovens manufacturing

One way to categorise nonwovens is by their methods of manufacture.  Nonwovens can be divided into three distinctive groups: those produced by dry-laid methods; wet-laid methods; or spun melt processes. Information of manufacture, properties and end uses are contained in the next three sections.

One of the major advantages of nonwoven manufacture is the speed at which fabric can be produced, especially when compared to the production rates of knitted or woven fabrics.  The effect of this is the reduction in the cost of manufacturing.

Dry-laid nonwovens

Dry-laid nonwovens are formed from staple fibres.  These fibres are then processed to create fibrous webs which have little mechanical integrity.   The webs are then bonded either by mechanical, thermal or chemical means.  Sometimes a secondary bonding process will also be applied (Fig. 3)

Fig 3

Figure 3 - Overview of dry-laid nonwoven manufacturing

Fibre selection and opening

Fibre selection and opening is the first stage of the nonwovens process.  More information can be found at

 http://web.utk.edu/~mse/Textiles/Dry%20Laid%20Nonwovens.htm

http://www.tatham-uk.com/fibreopening.php

Dry-laid web manufacture

There are two different methods of dry-laid web manufacture.  The method used depends on the desired fibre orientation, the method of bonding to be used (it is difficult to successfully mechanically bond short fibres) and the fibre length (Fig. 4).

Fig 4

Figure 4 - Air-laid web formation processes

Air-laid

Air-laid technology produces a randomly orientated fibrous web.

Airlaid short fibres of 1-15 mm and particles are dispersed in air by various means. A common method employs rotating blades, which produces a “cloud” of fibres within the airlay chamber. The fibres are then transported through the air toward a permeable conveyor belt under which suction is applied. This helps to gather the fibres onto the conveyor surface, where the web is formed (Fig. 5).

Fig 5a

Fig 5b

Figure 5 - Carding

More information on web formation can be found at

http://web.utk.edu/~mse/Textiles/Dry%20Laid%20Nonwovens.htm

http://www.edana.org/Content/Default.asp?PageID=41#drylaid

http://sst.umt.edu.pk/newsite/courses/Spring2010/TX-224/3-%20Non%20Woven%20Web%20formation.pdf

Dry laid bonding methods

There are three different types of bonding, mechanical, thermal, and chemical.  A variety of different processes come under these different headings.

Mechanical bonding

Hydroentanglement (spunlace) the fibres are mechanically entangled together by high velocity jets of water that are directed onto the web. The water pressure can be 20-600 bar. The jets entwine, Twist? and rearrange the fibres to create bonding and in some cases to introduce patterning effects. Patterns and apertures in the fabric are produced by altering the design of the conveyor sleeve surface (Fig.6) more information can be found at: http://web.utk.edu/~mse/Textiles/Spunlace.htm

Fig 6a

Fig 6b

 

Fig 6c

Figure 6 - Hydroentanglement: A diagram, B Machine, C end fabric

Needlepunching with Barbed Needles

Fibres are mechanically entangled by the reciprocation of barbed needles through the web. Sections of fibre are collected on the barbs of the needles (normally 3 barbs on each of the 3 edges of the needle) as they move up and down. This creates “pillars” of fibres in the thickness of the web that hold the structure together. To stop the whole web moving up and down with the needles as they reciprocate during the process, a stripper and a bed plate are provided (Fig.7).   More information can be found at http://web.utk.edu/~mse/Textiles/Needle%20Punched%20Nonwovens.htm   and http://www.textileworld.com/Articles/2008/September_2008/Nonwovens/Needlepunched_Nonwovens.html

Fig 7

Figure 7 - Needle punch

Thermally bonded

Thermal Bonding of thermoplastic fibres (that soften and melt when heated) can be carried out using heated calender rollers (Fig.8) or an oven, where hot air is convected through the web to bond it. The fibres are effectively fused together by melting (Fig.9). The proportion of fibres that are melted can be controlled to prevent the fabric from becoming too stiff or film-like. The temperature used in bonding has to be selected according to the melting temperature of the fibre.   More information can be found at http://web.utk.edu/~mse/Textiles/Thermal%20Bonding.htm

Fig 8

Figure 8 - Calender rollers

Fig 9

 

Figure 9 - Thermally bonded fibres

 

Adhesively bonded

Chemical Bonding of fibres involves   adding a wet chemical adhesive (binder) to the web by various means. One method is to saturate the web with the binder liquid by impregnation. Drying and curing follow to stabilise the binder. The properties of the fabric depend on the amount of binder that is added in relation to the weight of fibre, its physical properties and how it is distributed within the web (Fig.10).   http://web.utk.edu/~mse/Textiles/Chemical%20Bonding.htm

Fig 10

Fig 10b

Figure 10 - Two differing methods of Adhesive bonding

Wet-laid nonwovens

The principle of wetlaying is similar to paper manufacturing. The difference lies in the amount of synthetic fibres present in a wetlaid nonwoven.   A dilute slurry of water and fibres is deposited on a moving wire screen and drained to form a web. The web is further dewatered, consolidated, by pressing between rollers, and dried. Impregnation with binders is often included in a later stage of the process.

The strength of the random oriented web is rather similar in all directions in the plane of the fabric. A wide range of natural, mineral, synthetic and man-made fibres of varying lengths can be used. http://www.edana.org/content/Default.asp?PageID=41

More information can be found at

http://web.utk.edu/~mse/Textiles/Wet%20Laid%20Nonwovens.htm

Fig 11

Figure 11 - Wetlaid machinery

 Spunmelt nonwovens

In these processes webs are made directly from filaments spun from plastics in liquid form.

Spunbond

Spunbond: this is the most direct method of making a nonwoven. Continuous filaments, not staple fibres, are spun (extruded) directly from polymer chip. Normally, polymers are melt-extruded in the spunbond process. The formation of a web of continuous filaments deposited on the conveyor belt is assisted by suction. The web is then bonded directly by various means, normally thermal bonding (Fig. 12).  More information can be found at: 

http://web.utk.edu/~mse/Textiles/Spunbond%20Technology.htm

Fig 12 scale

Figure 12 - Spunbond equipment

Meltblown

Meltblown is similar to spunbond but produces much finer filaments. The hot, molten, liquid polymer is forced through nozzles to form a stream of polymer. At the nozzle tip, the filaments are picked up by hot, high velocity air streams that stretch the filaments by drag forces into very fine diameters. The filaments gradually cool as they travel across to the collector. The use of suction at the collector assists in web formation (fig.13).

http://web.utk.edu/~mse/Textiles/Melt%20Blown%20Technology.htm

Fig 13

Figure 13 - Meltblowing

Finishing treatments

There is an opportunity to meet the needs of the customer even more precisely by modifying or adding to existing properties. A variety of different chemical substances can be employed before or after binding, or various mechanical processes can be applied to the nonwoven after binding.

Nonwovens can be made conductive, flame retardant, water repellent, porous, antistatic, breathable, absorbent and so on - the list is a very long one. They can also, for example, be coated, printed, flocked or dyed, and can be combined with other materials to form complex laminates.  http://www.edana.org/content/Default.asp?PageID=43

More information can be found at

http://web.utk.edu/~mse/Textiles/Finishing%20of%20Nonwovens.htm

Nonwoven Applications

With such a diverse range of manufacturing methods coming under the heading of nonwovens it is unsurprising that nonwovens have a huge variety of potential applications owing to their differing features.  The properties of nonwovens include;


  • Abrasion resistant
  • Absorbent
  • Antistatic
  • Biodegradable?
  • Breathable
  • Colour fast
  • Conductive
  • Crease resistant
  • Dense
  • Drapeable
  • Dry cleanable
  • Durable
  • Dust free
  • Dyeable
  • Elastic
  • Filtration
  • Flame resistant
  • Foldable
  • Glueable
  • Heat sealable
  • Impermeable
  • Ironable
  • Kind to skin
  • Light
  • Lint free
  • Liquid repellent
  • Long-lasting
  • Mouldable
  • Non-conductive
  • Non-fading
  • Permeable
  • Porous
  • Printable
  • Protective (bacterial barrier)
  • Resilient
  • Rot and mildew resistant
  • Sewable
  • Smooth
  • Soft
  • Stable
  • Sterilisable
  • Stiff
  • Stretchable
  • Strong
  • Tear resistant
  • Washable
  • Weatherproof
  • Weldable

 

Major applications of Nonwovens

The major applications for nonwovens are shown in figure 14.  The chart represents the weight (tonnes) of nonwovens produced in each sector, rather than the monetary value.  Note the huge (and expanding) hygiene sector, and the large wipes sector, which is largely made up of disposable products.  Figure 15 shows how the industry is expanding as a whole.

More on the trends in the nonwoven market can be found at http://specialtyfabricsreview.com/articles/1108_f2_nonwovens.html

The home page of INDEX 14, the World’s Leading Nonwovens Exhibition is http://www.index11.org/en/index.php/ and http://www.index14.ch/en/

Fig 14 scale

Figure 14 - Major applications of nonwovens (% of tonnes)

Fig 15 Scale

Figure 15 - European Production of Nonwovens
(10³ tonnes)

Product Life: Disposable vs Durable

Many nonwoven products are disposable, thus issue relating to sustainability are very relevant to this expanding part of the industry.  More on sustainable nonwovens can be found at

http://www.extrusiongroup.com/2011/04/30/sustainable-nonwovens-set-rise-sharply/ and

http://www.sustainablenonwovens.net/

However some nonwovens are also designed for durable applications (fig. 16).  For more on durable nonwovens see

http://specialtyfabricsreview.com/articles/1109_expo4_nonwovens.html and

http://www.textileworld.com/Articles/2011/May/May_June_issue/Durable_Nonwovens.html

Fig 16 scale

Figure 16 - Disposable vs Durable nonwovens

The personal care and hygiene sectors

Produces in this sector are mainly disposable and include;

·         Baby diapers

·         Feminine hygiene products

·         Adult incontinence products

·         Dry and wet wipes

·         Cosmetic removal pads

·         Disposable underwear

More information can be found at http://www.nonwovens-industry.com/issues/2011-12/view_features/hygiene-components/

Medical

Produces in this sector are mainly disposable and include;

·         Infection Control (surgery): disposable caps, gowns, masks and shoe covers,

·         Wound Healing: sponges, dressings and wipes.

·         Therapeutics: Transdermal drug delivery, heat packs

More information can be found at http://www.fibre2fashion.com/industry-article/15/1445/nonwovens-as-medical-textiles1.asp and

http://www.ahlstrom.com/en/products/enduseApplication/medicalAndHealthcare/surgicalDrapes/Pages/Surgicaldrapefabrics.aspx

Household Domestic uses

Produces in this sector are often used as filters and are disposable including;

·         Wipes/mops

·         Vacuum cleaner bags

·         Washcloths

·         Kitchen and fan filters

·         Tea and coffee bags

·         Coffee filters

·         Napkins and tablecloths

·         Furniture construction: Insulators to arms and backs, cushion ticking, linings, stitch reinforcements, edge trim materials, upholstery.

·         Bedding construction: Quilt backing, mattress pad components, mattress covers.

·         Furnishings: window curtains, wall and floorcoverings, carpet backings, lampshades

More information can be found at http://www.edana.org/Content/Default.asp?PageID=151

Building industry

Products in this sector are often durable and high bulk fabric. Uses include;

·         Insulation and moisture management: roofing and tile underlay, thermal and sound insulation

·         Structural: Foundations and ground stabilisation

More information can be found at http://www.freudenberg-nw.com/ecomaXL/index.php?site=FNW_EN_building

Agriculture, Horticulture & Aquaculture

·         Insect damage protection: crop covers

·         Thermal protection: seed blankets

·         Weed control: impermeable barrier fabrics

More information can be found at http://www.fibre2fashion.com/industry-article/textile-industry-articles/agro-textiles-a-rising-wave/agro-textiles-a-rising-wave1.asp

Automotive and Transport

·         Interior Trim: boot liners, parcel shelves, headliners, seat covers, floorcovering, backings and mats, foam replacements. 

·         Insulation: exhaust & engine heat shields, moulded bonnet liners, silencer pads.

·         Vehicle performance: oil and air filters, fibre reinforced plastics (body panels), aircraft brakes.

http://www.inda.org/about-nonwovens/nonwoven-markets/automotive-transportation/

http://www.textileworld.com/Articles/2009/May/NW/nonwovens_enhance_car_performance.html

Geosynthetics

·         Asphalt overlay

·         Soil stabilisation

·         Drainage

·         Sedimentation and erosion control

·         Pond liners

http://www.textileworld.com/Articles/2011/January/Jan_Feb_issue/Geotextiles.html

Filtration

·         Air & gas filters

·         Liquid - oil, beer, milk, liquid coolants, fruit juices….

·         Activated carbon filters

http://www.textileworld.com/Articles/2009/March/NW/Primer_On_Nonwoven_Fabric_Filtration.html

Clothing

·         Personal Protection: thermal insulation, fire, slash, stab, ballistic, pathogens, dust, toxic chemicals and biohazards, high visibility workwear.

http://www.nonwovens-industry.com/issues/2012-06/view_breaking-news/dupont-opens-ballistics-testing-facility-in-india/

·         Stiffening and Shaping: linings and interlinings for conventional clothing and fashion, shoe components and clothing accessories.

·          Nonwovens do not fray or unravel so have much potential for fashion of the future.  However laundering of nonwovens can be problematic in some instances.  http://www.techexchange.com/library/Nonwoven%20Fabrics%20in%20Fashion%20Apparel.pdf and http://www.nonwovens.leeds.ac.uk/fashionwithnonwovens/

·         Durable Outerwear: synthetic leather & suedes (e.g. Alcantara®, Evolon®)

http://www.evolon.com/

Other applications of Nonwovens

Product protection & safety: Food delivery bags e.g. pizza, CD liners, food packaging (sandwiches, food trays, absorption pads for chilled products), airline headrests.

Manufacturing & Processing: industrial abrasives, conveyor belts, FRP’s, sound absorption, flame barriers, hot splash protection, air Conditioning?, anti-slip matting

Electronics & telecommunications: cable wrap and insulation, floppy disc liners, particle filters, ink jet printing substrates, satellite dishes, battery separators.

Sports equipment: Sleeping bags, tents, surf board composites.                 

Tear and Water Resistant Materials: bank notes, envelopes, signs, packaging.

Others: Luggage, handbags, shopping bags, pillowcases.

 The future of nonwovens

With the potential to create novel fabrics that respond to the every requirement of modern life the nonwovens sector will continue to expand.  Due to the highly technical and niche nature of some of the nonwoven products it is likely that a small area of the sector will remain UK and Europe based instead of relocating to developing counties (which have cheaper labour costs).  There are a variety of small companies actively engaged in R&D for nonwovens including http://www.nonwovens-innovation.com/ as well as university research groups http://www.nonwovens.leeds.ac.uk/.