4- non woven bonding systems

1

Non Woven Bonding system

Dr. Jimmy LamInstitute of Textiles & Clothing

By Hammad MohsinDepartment of Textiles, UMT Pakistan

Non-woven

Bonding systems in non-wovenNeedled feltsAdhesivesHeat bondingStitch bonding

Discussion

2

Introduction

In last section, we introduced what is non-woven fabrics, its advantages and application.Non-woven production

Fibre FabricTo 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 System1) 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.

3

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.

4

Bonding System2) Adhesives

For most nonwoven applications, fibre-to-fibre 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.

PhotoAdhesive

Adhesive bonding on non-woven

5

Bodning2) 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.

PhotosAdhesive Bonding

Adhesive bonding: a cellulosic wiper, with the adhesive applied in colour stripes and resin-impregnated fibreglass used to reinforce pipes

6

Heat BondingWhen 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.

PhotoHeat bonding

Melt-bonding at selected points to give extra stability to a spun bonded polypropylene geotextile

7

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.

PhotoStitch bonding

Carpet underfelts are often stitch-bonded, and may incorporat a layer of loosely woven hessian for extra length

8

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)

AnswerDefinition

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, 7th Edition

9

Another definitonSource: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-wovenRaw materialNon-woven materials are nowadays mainly produced from man-made fibers. Two synthetic polymers dominate the market: polypropylene and polyesters (mainly PET).

ApplicationsNon-woven materials are used in numerous applications, including:Hygiene

Baby diapersFeminine hygieneAdult incontinence products

WipesDomestic Technical

FiltersGeotextilesCarpet backing Composites

10

ManufacturingStaple non-wovensStaple 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-wovensSpunlaid 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).

BondingBoth 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