4 non woven bonding systems


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4 non woven bonding systems

  1. 1. 1Non Woven Bonding systemDr. Jimmy LamInstitute of Textiles & ClothingBy Hammad MohsinDepartment of Textiles, UMT PakistanNon-wovenBonding systems in non-wovenNeedled feltsAdhesivesHeat bondingStitch bondingDiscussion
  2. 2. 2IntroductionIn last section, we introduced what is non-wovenfabrics, its advantages and application.Non-woven productionFibre FabricTo make non-woven fabric, the first step is webformation, to make a strong and parallel web.The second step called “bonding” is to combinedifferent webs together to make a stronger layers (withdifferent thickness and fabric weight) for particular enduses.Bonding System1) Needled feltsFibres which have no directionalfrictional properties need to bemechanically entangled in order to formfelts.This is done using barbed needles.The products of needle felting are usedfor carpets, underfelts, upholstery, andblankets.
  3. 3. 3Photos for needle punching (bonding)Needle punching. The barbed needle tanglestogether some fibres from each layer of the webto make a stronger web.Photos for needle punching (bonding)Cross section of a needle-punched bonded fabric.
  4. 4. 4Bonding System2) AdhesivesFor most nonwoven applications, fibre-to-fibre friction does not provide enoughstrength.Adhesive can be effective in holding thefibres together.It is, however, important not to use too muchadhesive or the natural properties of thefibres may be masked, giving the fabricproperties of the adhesive rather than of thefibres.PhotoAdhesiveAdhesive bonding on non-woven
  5. 5. 5Bodning2) AdhesiveThe adhesive can be applied to the web as aprinted pattern or as a sprinkling of powder.The properties of an adhesive-bondednonwoven depend to quite a large extent onthe properties of the adhesive polymer used.Commonly used adhesives are polyvinylacetate (PVA glue) polyacrylonitrile, PVC.PhotosAdhesive BondingAdhesive bonding: a cellulosic wiper, with the adhesive applied in colour stripesand resin-impregnated fibreglass used to reinforce pipes
  6. 6. 6Heat BondingWhen a web of thermoplastic fibres (polyester, nylon) orfilament is heated, the fibres cross over each other atmany points, there are many rigid welding spots innonwoven fabric.This makes heat-bonded fabrics rather stiff andinextensible.In order to produce a softer fabric without the use ofadhesives, thermoplastics fibres with lower melting pointare blended in the web with fibers with higher meltingpoint.On heating, only the low melting point fibers melt.This way, fewer weld points are formed and the resultantfabric has more desirable textile properties.Such melt-welded fabrics are called Melded fabrics.PhotoHeat bondingMelt-bonding at selected points to give extra stability to a spunbonded polypropylene geotextile
  7. 7. 7Stitch BondingWebs may also be given extra strength by stitching themthrough with yarns.Such structures are usually more flexible and less paper-like than heat-bonded or adhesive bonded nonwovens.Stitch bonding is based on principle of warp knitting butwith needles designed to stitch through webs of variousthickness.A web of fibres or web of yarns or a cheap fabric forms thebase.Sharp-pointed needles pierce the base and loop bindingyarns through it.In this way, relatively cheap but stable fibres, with orwithout pile, can be produced.PhotoStitch bondingCarpet underfelts are often stitch-bonded, and may incorporat a layer ofloosely woven hessian for extra length
  8. 8. 8ConclusionIn this section, we discuss the bondingsystems for non-woven fabrics.They are:1. Needle punching (mechanical action)2. Adhesive bonding (chemical action)3. Heat bonding (for thermoplastic fibres)4. Stitch bonding (mechanical, warp knitting)AnswerDefinitionNon-woven fabric. A textile structure produced by bonding orinterlocking of fibres, or both; accomplished by mechanical,chemical, thermal or solvent means and combinations thereof.This excludes woven, knitted and tufted fabrics.Nonwoven webs may be made from fibers by dry formingthrough carding, garnetting or air laying; also made by wetforming.Among the means used for bonding nonwoven textile structuresare adhesive impregnation or spraying, thermal bonding,needle punching, spun lace and spunbonded processes.Source: Fairchild Dictionary of Textiles, 7th Edition
  9. 9. 9Another definitonSource:Wikipedia, free encyclopediaNon-woven textiles are those which are neitherwoven nor knit, for example felt. Non-wovens aretypically not strong (unless reinforced by a backing),and do not stretch. They are cheap to manufacture.Non-woven fabric is manufactured by putting smallfibers together in the form of a sheet and then bindingthem either mechanically (as in the case of felt), withan adhesive, or by interlocking them with serratedneedles such that the inter-fiber friction results in astrong fabricMaterials for non-wovenRaw materialNon-woven materials are nowadays mainly produced from man-made fibers. Twosynthetic polymers dominate the market: polypropylene and polyesters (mainlyPET).ApplicationsNon-woven materials are used in numerous applications, including:HygieneBaby diapersFeminine hygieneAdult incontinence productsWipesDomesticTechnicalFiltersGeotextilesCarpet backingComposites
  10. 10. 10ManufacturingStaple non-wovensStaple non-wovens are made in two steps. Fibers are first spun, cut to a fewcentimeters length, and put into bales. These bales are then dispersed on aconveyor belt, and the fibers are spread in a uniform web by a wetlaid processor by carding.Spunlaid non-wovensSpunlaid non-wovens are made in one continuous process. Fibers are spunand then directly dispersed in a web by deflectors. This technique leads tofaster belt speeds, and cheaper costs. Several variants of this concept areavailable, but the leading technology is the Reicofil machinery, manufacturedby Reifenhaüser (Germany).BondingBoth staple and spunlaid non-wovens would have no mechanical resistanceper se without the bonding step. Several methods can be used:thermal bonding: calendering through heated rollers (called spunbond whencombined with spunlaid)hydro-entanglement: mechanical intertwining of fibers by water jetsneedlefelt: mechanical intertwining of fibers by needles