Pilling 1

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ANTI PILLING TREATMENTS INTRODUCTION The surface appearance of a textile material is very important to the consumer. Pills are an aesthetic and physical nuisance. The pilling of textile materials fabrics refers to an appearance caused by bunches or balls of tangled fibers held to the surface. This unpleasant appearance can seriously compromise the fabrics acceptability for apparel. This paper reviews about new techniques and developments in anti pilling treatments from fibre stage and mechanical and chemical treatments that prevail over pilling problem.

PILLING MECHANISM The pills are formed only during wear ,wash and tear due to abrasion affecting appearance, touch and handle of fabrics. The mechanism of pilling goes through the following four stages: 1. Fuzz formation on fabric surface. 2. Entanglement of fibers in the fuzz with each other. 3. Densification of these entanglements into small balls called pill. 4. Shedding away of pills.

Fuzz formation is result of constant gentle abrasion. In a garment, it is usually observed near the abrasion areas such as near the pocket, collar. etc. PILLING PERFORMANCE OF SYNTHETIC AND NATURAL FIBRES Most fabrics exhibit some degree of pilling. Fabrics constructed entirely of natural fibers are low-pill because the pills are smaller and fall away before they are noticeable. A woven fabric is, by its very nature, of a tighter construction, so it is more difficult for fibers to migrate to the surface and cause pilling. Synthetic knits exhibit pilling problems because of their loose construction, and knits of synthetic staple fibers contain numerous eligible free fiber ends that begin the pilling process . Filament fabrics have no free ends to migrate, so no pills can form.

The pilling performance of fibres is shown in the graph 1

FACTORS AFFECTING PILLING: The pilling tendency of fabrics depends on denier of fibres, twist factor of yarn, construction of fabric and processing steps used during the manufacture of fabric as under: 1. Denier of fibres: Fine denier fibres tend to pill more as they possess less stiffness. Secondly, fibres per unit length of yarn will be more in a case of fine denier compared to the yarn made from coarser denier so that there will be more fibre ends exposed rendering the fabric more prone to pilling. 2. Twist factor of yarn: The yarn with lower twist factor below 3.4 will pill more than the yarn with higher twist factor. It is therefore necessary to choose slightly higher twist factor for single /doubled yarn if it would not adversely affect the feel of the fabric. The double yarn exhibits less pills. 3. Fabric construction: Closed weave fabric with a high sett, pills less. Plain weave fabric with maximum yarn intersections gives better pill rating. Weaves with longer floats like twills and sateen have less binding points so pill more. 4. Processing: Processing steps involving both mechanical and chemical operations which would render fabric surface clean and hair free play a vital role in minimizing pilling. For effecting control on pilling, precautions will have to be taken from early stages of processing. Pilling can be prevented or considerably reduced by fiber blends, appropriate yarn fabric construction, suitable finishing or by using low-pilling synthetic fibers.

ANTI PILLING FIBRES The low-pilling effect in synthetic fibers is obtained by chemical modification or by using low molecular weight spinning raw materials. The use of longer staple fibers in worsted yarns compared to shorter fibers used in cotton spun yarns may also reduce pilling. The finer the fiber the less pilling occurs, as flexing elasticity is reduced. In the case of micro staple fibers the fibers break off. Thus pilling is avoided. Also the use of trilobal, pentalobal or other kinds of profiled fiber types can reduce pilling. A cross-section of the profiled fibers shows that they are not round likes standard fibers, but shaped with special spinnerets.

Birla Acrylic has come out with an innovative fibre which reduces pill formation over repeated usage. Birla Acrylic Anti-Pill fibres reduce pilling in fabrics and subsequently slow down apparel aging. Birla Acrylic delivers a high pilling grade of 4-4.5 (on a scale of 5) following ICI Pill Box Test. The Anti-Pill fibre has been specifically engineered to have sustainable anti-pilling performance throughout the lifetime of the apparel. Products manufactured out of Birla Acrylic anti-pill fibers stay new and elegant even after repeated washing cycles. Birla Acrylic Anti-Pill fibers can be blended with both natural and synthetic fibres like wool, viscose etc. In blends with other fibers, it enhances the pill performance of blends. It is available in a range of denier (1.2 Den to 2.5 Den) and cut-length (38, 44, 51, 64 mm). It is available in both Tow/Fiber and Bright/Semi Dull options.

Trevira 350 is a low-pill polyester fibre for the weaving and knitting sectors. The special characteristics of Trevira 350 are embedded in the chemically modified polymer, which has hydrolysable bonds in the polyester chain. The bonds dissolve during the dyeing process, substantially reducing the transverse strength of the fibre. This reduction in tenacity is intended to lead to any pills that form with wear breaking off. This occurs early in their development.

DuPont now introduces soft, versatile CoolMax Alta, a new low-pill product for use in 100%constructions. The product combines the processability of CoolMax with the consumer value of low-pill and moisture management while maintaining that next-to-the-skin softness. DuPont has modified the chemical arrangement of the polymer at the point of manufacture .CoolMax Alta provides pill ratings of 3 or better, (ASTM D3512-82 where 1 is severe pilling and 5 is no pilling), equal to or better than other synthetics and even wool.

FIBRES TYPES WITH ROUND CROSS SECTIONS FIBRE CHARACTERISTIC S INITIAL STATE Thickness dtex Maximum tensile loadcN/tex Maximum tensile load extension% Relative loop resistance % Blending resistance(turns) After 4 hours of hightemperature dyeing Thickness dtex Maximum tensile

NORMAL HOLLOW PILL SUPE PILL RESISTANT RESISTANT

3.3 50 35 95 150,000

3.3 45 40 90 150,000

3.3 40 45 90 50,000

3.0 30-33 32-37 80 900-1,300

3.6 45

3.6 40

3.6 35

3.0 22

loadcN/tex Maximum tensile load 35 40 40 25 extension% Relative loop 85 80 80 70 resistance % Blending 70,000 120,000 20,000 1,000 resistance(turns) This table clearly shows that mechanical and technological properties of fibres can be altered by modifying the cross sectional shape and by adding copolymers (super pilling resistant).It is important to reduce flexing resistance so as to decrease pilling. When pills are about to be formed, the fibres that have been pushed or pulled out should preferably break off, a circumstance which depends on maximum tensile load and elongation behaviour.-Evidence gained from experience shows that in the finished product, super pilling fibres should have a thickness/maximum tensile load of 30 cN/tex as well as a maximum load extension of 35%.Fig illustrates the effects that can actually be achieved in similarly constructed plain woven materials made exclusively of one type of fibre. The curves of the graph show that pills are formed when fabric is exposed to abrasion, which is also the case for wool. The number of pills developed per unit area, however varies considerably depending on the type of fibre. If abrasion continues after the maximum number of pills per unit area has been reached, pills break off. Therefore total number of pills will decrease, despite the formation of new ones.If normal polyester fibres are used, still many pills will remain visible on the fabric, whereas in the other three types of fibre,pills will break off almost entirely or even entirely. Chemistry of anti-pilling finishes For all kinds of finishes, special product groups are known and listed in catalogues. There is, however, no group of anti-pilling products in the International Textile Auxiliaries Buyers' Guide. The reason is not that this finish is not important enough. This astonishing fact may be explained by: the large variety of parameters that influence the pilling behaviour, the corresponding variety of approaches to anti-pilling finishes, the circumstance that textile auxiliary producers mostly recommend products that are primarily used for other purposes for anti-pilling finishes, there are only a few general recipes for anti-pilling finishes, the need for specific solutions for every type of article, including all other finishing components PHYSICAL PROCESSES FOR REDUCING PILLING Shearing or cropping Cropping and shearing reduce pilling by reducing the length of the projecting fibres. Cropping and shearing give a much superior handle to singeing. Singeing

Singeing with shearing / cropping and optimum heat setting would reduce pilling. The parameters during singeing will have to be optimized with respect to speed, quality of flame and number of passages to obtain the fabric with the desired level of pilling resistance

Brushing In the case of tighter-woven fabric made from highly twisted yarn, loose fibres can be brought to the surface of fabric by means of brushing, where they can be removed by a close shearing. Such a procedure is not possible on loosely spun yarns with a fluffy surface.

Thermosetting Heat-setting tends to produce smooth fabric laying down the individual surface fibres to the fabric body and polyester fibres are rendered slightly stiffer so that even at a later stage tend to entangle less.

Special treatments _ Sanding of the fabrics before brushing and shearing _ Wet milling with soap for three hours, followed by brushing and shearing

_ Heat treatment on an enclosed tenter frame at 204C _Hot-impregnati