Non Woven Fabric (2) Dr. Jimmy Lam Institute of Textiles & Clothing
Non-woven Bonding systems in non-woven Needled felts Adhesives Heat bonding Stitch bonding Discussion
Introduction In last section, we introduced what is non-woven fabrics, its advantages and application. Non-woven production Fibre Fabric To make non-woven fabric, the first step is web formation, to make a strong and parallel web. The second step called bonding is to combine different webs together to make a stronger layers (with different thickness and fabric weight) for particular end uses.
Bonding System 1) Needled felts Fibres which have no directional frictional properties need to be mechanically entangled in order to form felts. This is done using barbed needles. The products of needle felting are used for carpets, underfelts, upholstery, and blankets.
Photos for needle punching (bonding) Needle punching. The barbed needle tangles together some fibres from each layer of the web to make a stronger web.
Photos for needle punching (bonding) Cross section of a needle-punched bonded fabric.
Bonding System 2) Adhesives For most nonwoven applications, fibre-tofibre friction does not provide enough strength. Adhesive can be effective in holding the fibres together. It is, however, important not to use too much adhesive or the natural properties of the fibres may be masked, giving the fabric properties of the adhesive rather than of the fibres.
Photo Adhesive Adhesive bonding on non-woven
Bodning 2) Adhesive The adhesive can be applied to the web as a printed pattern or as a sprinkling of powder. The properties of an adhesive-bonded nonwoven depend to quite a large extent on the properties of the adhesive polymer used. Commonly used adhesives are polyvinyl acetate (PVA glue) polyacrylonitrile, PVC.
Photos Adhesive Bonding Adhesive bonding: a cellulosic wiper, with the adhesive applied in colour stripes and resin-impregnated fibreglass used to reinforce pipes
Heat Bonding When a web of thermoplastic fibres (polyester, nylon) or filament is heated, the fibres cross over each other at many points, there are many rigid welding spots in nonwoven fabric. This makes heat-bonded fabrics rather stiff and inextensible. In order to produce a softer fabric without the use of adhesives, thermoplastics fibres with lower melting point are blended in the web with fibers with higher melting point. On heating, only the low melting point fibers melt. This way, fewer weld points are formed and the resultant fabric has more desirable textile properties. Such melt-welded fabrics are called Melded fabrics.
Photo Heat bonding Melt-bonding at selected points to give extra stability to a spun bonded polypropylene geotextile
Stitch Bonding Webs may also be given extra strength by stitching them through 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 but with needles designed to stitch through webs of various thickness. A web of fibres or web of yarns or a cheap fabric forms the base. Sharp-pointed needles pierce the base and loop binding yarns through it. In this way, relatively cheap but stable fibres, with or without pile, can be produced.
Photo Stitch bonding Carpet underfelts are often stitch-bonded, and may incorporat a layer of loosely woven hessian for extra length
Conclusion In this section, we discuss the bonding systems 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)
One more thing After these two sections on nonwoven, can you define what nonwoven fabric is and their applications?
Answer Definition Non-woven fabric. A textile structure produced by bonding or interlocking 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 forming through carding, garnetting or air laying; also made by wet forming. Among the means used for bonding nonwoven textile structures are adhesive impregnation or spraying, thermal bonding, needle punching, spun lace and spunbonded processes. Source: Fairchild Dictionary of Textiles, 7 th Edition
Another definiton Source:Wikipedia, free encyclopedia 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), and do not stretch. They are cheap to manufacture. Non-woven fabric is manufactured by putting small fibers together in the form of a sheet and then binding them either mechanically (as in the case of felt), with an adhesive, or by interlocking them with serrated needles such that the inter-fiber friction results in a strong fabric
Materials for non-woven Raw material Non-woven materials are nowadays mainly produced from man-made fibers. Two synthetic polymers dominate the market: polypropylene and polyesters (mainly PET). Applications 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
Manufacturing 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. Spunlaid non-wovens Spunlaid non-wovens are made in one continuous process. Fibers are spun and then directly dispersed in a web by deflectors. 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). 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: calendering through heated rollers (called spunbond when combined with spunlaid) hydro-entanglement: mechanical intertwining of fibers by water jets needlefelt: mechanical intertwining of fibers by needles