Polyester fiber processing

2. POLYESTER FIBRES Introduction: Polyester are polymer made by a condensation reaction taking place between small molecules, in which the linkage of the molecules occurs through the formation of ester groups. Polyester is commonly made by interaction of a dibasic acid with a dihydric alcohol: HOOC — X— COOH + HO — Y — OH—→ — OC — X — COO — Y — OCO — X — COO — Y —OCO Today, polyethylene terepthalate fibres are being made in many countries, and modified forms of this fibre are also produced

3. Processing The basic finishing processes for 100% PET polyester filament yarn fabric may be arranged in the following three sequences: 1. Scour – heat-set – dye 2. Heat-set – scour – dye 3. Scour – dye – heat-set Loom stains and other forms of contamination are difficult to remove from cloth which has been heat-set, and it is preferable to scour before heat-setting. Also, goods which have not been heat- set before dyeing will tend to shirk during dyeing, and the dyed goods will be subjected to high temperatures after dyeing. For these reasons, sequence (1) is the most generally useful.

4. Sequence (2) eliminates a drying process and is suitable for fabrics which are perfectly clean in the loom state. It is however, rarely used for PET polyester fabric except in the case of curtain nets. If sequence (3) is used, some stiffening of the fabric is likely to occur following heat-setting. The degree of stiffening depends on the construction of the fabric and on the tensions which are developed during setting.

5. Scouring: PET polyester fibres are supplied in a high state of cleanliness, and it is generally unnecessary to scour the material prior to dyeing. If, however, a batch of fibre should become so dirty as to require scouring, the bath may be set with: Scouring recipe: Water — 1000 parts Soda ash — 2 parts Detergent, such as textile soap, Or lissapol C, D, NC, or ND — 1 parts

6. The temperature is rise to 70˚c for 15-30 minutes and, after scouring, the goods should be rinsed thoroughly to eliminate all traces of alkali. A small quantity of acetic acid may be added to the final rinse. PET polyester goods will often acquire and stains during manufacture, including after-waxing agents applied to sized warp yarns, loom stains and other forms of soiling. If goods are heat set before removal of these stains, subsequent cleaning of the goods will become difficult and perhaps impossible. It is preferable, therefore to scour goods before heat-setting. A bath of the following composition is commonly used: Water — 1000 parts Soda ash — 2-3 parts Or caustic soda (flake) Detergent, such as textile soap, Lissapol C, D, NC or ND — 1-2 parts Fabric of relatively open structure, such as voiles, marquisettes and lenos may be scoured in a shallow which at temperatures below 60˚c.

7. Bleaching: The natural white color of PET polyester fibers is usually satisfactory for most purposes, and bleaching is unnecessary. When fabric are to be finished white a slightly improved color may be obtained by bleaching in a bath set with 1-3 parts of sodium chlorite per 1000 parts of water. Other common bleaching agents have little or no effect on the color of PET polyester fibres. The best results are obtained by making use of fluorescent brightening agents. Those used with PET polyester fibres commonly have the following characteristics: 1. A relatively high dyeing temperature is required. One result of this is that they are virtually non-effective as additives in domestic washing powders. 2. High wet fastness. This ensures little loss under normal washing conditions, obviating the need for restoration of the white during washing. 3. Light fastness is high enough for all apparel uses, and in most cases is suitable also for furnishings curtains.

8. Fluorescent brightening agents are applied by the methods used in dyeing with disperse dyes, i.e. 1. Application at the boil, without carrier. 2. Application at or near the boil, with carrier. 3. High temperature application (130˚c), without carrier. 4. Applications by pad-thermo fix techniques. 5. The method selected will depend upon the type of machinery available, and the structure of the fabric. Most fabrics may be handled on a beam-dyeing machine at or above 100˚c, while a jig may be used for the more stable woven fabrics. Rope processing in the winch is often used, especially for warp knitted fabric. 6. Techniques recommended for obtaining a good white finish on PET polyester and blends are outlined below.

9. 100% PET polyester and PET polyester / Nylon Blends: Warp-knitted Fabrics: An excellent white is obtained by treating the heat-set fabric with acidified sodium chlorite, followed by the application of a fluorescent brightening agent at 130˚C.or 100˚C.With a compatible carrier, on a beam-dyeing machine. With most brightening agents, a good white can be obtained by a single-bath method in which the fluorescent brightening agent and compatible carrier are included in the sodium chlorite liquor.

10. Weft-knitted Fabrics: Weft-knitted fabric may be handled on the winch, using similar techniques. Woven Fabric: The beam-dyeing machine is recommended for bleaching woven fabrics. Alternatively, the jig may be used, the concentration of chlorite bleaching chemical being increase by some 20% to compensate for the shorter liquor.

11. PET polyester / Cellulosic Fibre Blends: Chemical bleaching should be employed, especially when the cellulosic component is cotton. For best results, fluorescent brightening agents should also be applied for both components of the blend. Several methods of chemical bleaching may be used, the choice depending on the result required and the equipment available. Acidified sodium chlorite provides most effective single stage bleach, and a high white is obtained from a chlorite bleached followed by peroxide bleached. A good result is also obtained from hypochlorite bleach followed by alkaline hydrogen peroxide. Hypochlorite or peroxide used alone as a single stage process will given a white suitable for many purposes, e.g. as ground for subsequent dyeing. Processes excluding chlorite are generally more suitable for color woven goods. PET polyester / flax blends may be bleached according to these general principles, but more intense treatment is required.

12. PET polyester / Wool Blends: The PET polyester component cannot be bleached with chlorine compounds in the presence of the wool component. Chemical bleaching of PET polyester / Wool blends is virtually restricted, therefore, to the bleaching of the wool. Hydrogen peroxide is the preferred agent, and bleaching is carried out after a fluorescent brightening agent has been applied to the PET polyester component. This corrects any yellowing of the wool which may have occurred during the application of the agent to the PET polyester fibre.

13. Pre-Setting: Unset PET polyester filament yarn will shrink when allowed to relax in boiling water, commonly by some 7%. At 130˚., shrinkage is of the order of 10%. If unset yarns in package form are subjected to any process, such as dyeing, involving elevated temperature, the shrinkage will bring about consolidation of the package. In dyeing, this restricts the even flow of dye liquor and causes unlevel dyeing.

14. Heat-setting: The purpose of heat-setting is to stabilizer the fabric to the effects of heat treatment which it may receive in subsequent finishing processes, in making-up, in use. The selection of heat-setting conditions is controlled, therefore, by the intended end-use of the fabric and by the thermal history of the yarns from which it is constructed. For PET polyester fabrics, the heat setting temperature should be higher than the temperatures which are to be used in pleating, embossing or calendaring, so as to eliminate the possibility For PET polyester fabrics, the heat setting temperature should be higher than the temperatures which are to used in pleating, embossing or calendaring, so as to eliminate the possibility of uncontrolled shrinkage in these processes. It should be emphasized that the ability of PET polyester fiber to accept a permanent set is not influenced by the temperature of prior heat-setting. In this respect, PET polyester fibers differ from some other synthetic fibers.

15. Steam setting: Pressure steaming is not recommended for the setting of PET polyester fabrics, because of variation between the inside and the outside of the batch in the degrees of shrinkage and restraint which are produced.

16. Hot-Air-setting: A hot-air-setting is commonly used in heat-setting PET polyester filament fabrics. The pin stenter is usually preferred fro the setting of woven fabrics, but for fabrics in which a pin- marked selvedge is unacceptable, the clip stenter may be used in association with cylinder setting (see below). There are difficulties associated with the control of warp shrinkage in clip stenters. The clips tend to mark the selvedges setting, and tight selvedges may be torn from the body of the fabric. Local cooling at the selvedges is also more severe in the clip than in the spin stenter, and may produce marked unlevelness in subsequent dyeing.

17. Cylinder setting: Cylinder of cylinder-blanket setting machines is used principally in the stabilization of heavy industrial PET polyester fabrics. Where stenters could not withstand the high tensions developed in setting. This method is also used with fabrics such conjunction with stentering, it is also used to produce the exceptionally uniform finish which is required for PET polyester base fabrics which are to receive a plastic coating.

18. Heat-setting Conditions: PET polyester filament fabrics are commonly set by exposure for 10-30 seconds in the hot zone of the setting stenter. The extremes of this range correspond with lightweight fabrics of less than 68 g/m2 (2 oz./sq.yd.2) and with heavy fabrics of up to 203 g/m2 (6 oz. /yd.2). The following table suggests setting finishing of a wide range of PET polyester filament fabrics:

19. Fabric Fabric Class Class Method Method Setting temp. Setting temp. ( (° °C.) C.) Shrinkage warp Shrinkage warp Allowance (%) Allowance (%) weft weft Pin stenter Pin stenter 210 - 220 210 - 220 3 - 5 3 - 5 3 - 5 3 - 5 1 1 2 2 3a 3a 3b 3b 4 4 5 5 Pin stenter Pin stenter 200 - 210 200 - 210 3 - 5 3 - 5 3 - 5 3 - 5 Pin stenter Pin stenter 150 - 160 150 - 160 0 0 0 0 Pin stenter Pin stenter 150 - 200 150 - 200 0-5 0-5 0-5 0-5 Clip stenter plus Clip stenter plus 150 - 160 150 - 160 0 0 0 0 Cylinder Cylinder 200 200 Free Free Free Free Cylinder Cylinder 210 210 10 approx. 10 approx. Free (15 Free (15 approx.) approx.)

20. Class 1 includes leno curtain fabrics and similar very open structures. Class 2 includes the majority of PET polyester filament woven fabrics (taffetas, twills, satins, etc.) Class 3 includes color-woven fabrics. The majority of fabrics made from high-temperature or carrier dyed yarns are stable to making-up and to mild laundering conditions. Fabric properties such as handle and crease recovery are, however, generally improved by the mild setting treatment suggested for Class 3a. Fabrics made from yarns dyed by other methods or which contain unset white yarns fall into Class 3b, and should be heat- set at the highest temperature permitted by the sublimation of the dyestuffs used. Class 4 includes fabrics for which completely free shrinkage is not permissible, but which must be finished free from pin or clip marks. Class 5 includes fabrics in which shrinkage is desirable, such as sailcloth’s, or which are too heavy for stenter processing.

21. Dyeing: PET polyester fibres are hydrophobic, and dyeing of useful depth are obtained by using those classes of dyestuffs which are substantially insoluble in water. These include the disperse dyestuffs, azoic dyestuffs (applied by a modified technique), and a limited number of vat dyes. Disperse dyestuffs provide build-up and color fastness that is adequate for most purposes, and a wide range of colors is available. Azoic dyestuffs produce a range of bright reds and maroons, a black and a navy blue, all of which have good fastness to sever washing, The usefulness of the azoic reds and maroons is limited, however, by their tendency to be dulled and to lose rubbing fastness after steam setting or heat setting processes

22. Vat dyestuffs yield a limited range of shades ,one or two of which are very bright , but they build up to only medium depths .PET polyester fibres have high affinity for disperse dyestuffs but the rate of diffusion of these dyestuffs in the fibre is relatively low. The rate of dyeing may be raised to a commercially accept able level either by working at the boil in the presence of an accelerating agent or carrier, or by dyeing under super atmospheric pressure at temperatures in the region of 130˚C. The high temperature dyeing method is preferable and should be used where possible, in order to take advantage of the excellent leveling action obtainable under these conditions. This technique also avoids the adverse effect of certain carriers on the light fastness of some dyestuffs. The full range of available disperse dyes can be applied at high temperature; whereas some of the newer disperse dyes do not build up well when dyed at the boil in the presence of a carrier. Disperse and selected vat dyestuffs may also be applied to piece goods by a pad-back technique, using dry heat at temperatures in the range 190- 215˚C.

23. Printing: • 100% PET polyester woven Fabric Fabrics woven from 100% PET polyester fibre yarn are usually printed with disperse dyestuffs, although a limited number of vat dyestuff may be used. The disperse dye provide a wide range of bright and deep shades, but the choice of individual dyestuffs is governed not only by the projected end-use, but also by the method to be used in fixing the color on to the fibre.

27. • Methods of Color Fixation • Three methods are commonly used for the fixation of printed colors on to PET polyester fabrics: – Prolonged steaming (1-2 hours) at atmospheric pressure, using a carrier to promote dyestuff migration. – Steaming for 20-30 minutes in a high pressure star-frame steamer, using high-temperature steam (1.4-2.0 kg/cm²; 20-28 lb. /in.²). – Fixation by treatment for 30-90 second in dry heat (190-200˚C.), using a stenter or backing oven. • High-temperature steaming and dry heat process both give excellent color yields. Low pressure steaming is the least effective of the three methods, but it makes use of conventional equipment.

28. Hydro extraction: Almost all the moisture in a wet PET polyester fabric is held mechanically in the inter fibre spaces, and most of it can be removed in hydro extraction. The quantity of water absorbed by the fibre itself is very small.

29. Drying: PET polyester fabrics are readily dried at 120˚C. and are normally handled on pin or clip sentres. Care must be taken to ensure that the fabric is not stentered under heavy tension. If it is necessary to remove scouring creases, the damp fabric should be stentered out, without overfeed, to a width which exceeds the scoured width by 7-14 mm per m (¼-½ in. per yd.), and then drier at 140-150˚C. Relaxed drying methods are preferred for caustic soda softened fabrics and some yarn dyed fabrics.

30. Properties of the polyester: 1) It is resists wrinkling. 2) It is easy to launder. 3) It dries quickly. 4) It is resistant to stretching and shrinking.

31. Uses: Polyester is used to make most forms of clothing like shirts, running shorts, track pants, windbreakers, and lingerie. It can also be made into curtains and draperies.

32. Care of your polyester garment: 1.Machine-wash your fabric in cold water. 2.Wash with light colors. 3.Use a gentle cycle while washing. 4.Tumble dry with the setting low. 5.Do not bleach. 6.If needed, iron with a cool iron.

33. Polymer Formation: Polymer Formation: Polyethylene Teraphthalate (PET) is a condensation polymer and is industrially produced by either terephthalic acid or dimethyl terephthalate with ethylene glycol. Other polyester fibers of interest to the nonwovens field include: (a) Terephthalic Acid (PTA), produced directly from p-xylene with Polyethylene Teraphthalate (PET) is a condensation polymer and is industrially produced by either terephthalic acid or dimethyl terephthalate with ethylene glycol. Other polyester fibers of interest to the nonwovens field include: (a) Terephthalic Acid (PTA), produced directly from p-xylene with bromide-controlled oxidation. bromide-controlled oxidation. (b) Dimethyl Terephthalate (DMT), made in the early stages by esterification of terephthalic acid. However, a different process involving (b) Dimethyl Terephthalate (DMT), made in the early stages by esterification of terephthalic acid. However, a different process involving two oxidation and esterification stages now accounts for most DMT. two oxidation and esterification stages now accounts for most DMT. (c) Ethylene Glycol (EG) initially generated as an intermediate product by oxidation of ethylene. Further ethylene glycol is obtained by reaction of (c) Ethylene Glycol (EG) initially generated as an intermediate product by oxidation of ethylene. Further ethylene glycol is obtained by reaction of ethylene oxide with water. ethylene oxide with water.

34. Chemistry of Polyester fiber Chemistry of Polyester fiber + HOOC COOH CH3OOC COOCH3 CH3OH Terephthalic Acid Dimethyl Terephthalate + CH3OOC COOCH3 HOCH2CH2OH Ethylene Glycol + HOCH2CH2OOC COOCH2CH2OH CH3OH Bis(2-Hydroxyethyl) Terephthlate Polymerization O O O O C C OCH2CH2O C C OCH2CH2O n Polyester

35. General Properties of Fiber General Properties of Fiber Filament Yarn Staple and tow Regular tenacity High tenacity Regular High tenacity Property tenacity 0.35-0.5 0.62-0.85 0.35-0.47 0.48-0.61 breaking tenacity, N/tex 24-50 10-20 35-60 17-40 breaking elongation 88-93 90 75-85 75-85 elastic recovery at 5% elongation, % 6.6-8.8 10.2-10.6 2.2-3.5 4.0-4.9 initial modulus, N/tex 1.38 1.39 1.38 1.38 specific gravity 0.4 0.4 0.4 0.4 Moisture regain, % 258-263 258-263 258-263 258-263 Melting temperature, o C

36. Other Properties of Polyester Fiber Fineness of polyester textile: Fineness of polyester fiber is also controllable. X-Sectional shape: Normal cross sectional shape is round but it is also made triangular, elliptical or pentagonal. Normally it is white but could be of any color if color is added during spinning. Extensibility: Extension at break varies from 20% to 30 %. Good recovery from extension. Due to good extension, strength and functional property polyester is widely used as sewing thread in the garment industries. Resiliency: Polyester textile shows good resiliency property. It does not crease easily and any undue crease can be recovered easily. Dimensional Stability: Polyester fiber is dimensionally stable. It could be heat-set at around 200 degree C. heat set polyester fiber does not shrink or extended. Action of bleaching agents: It is not damaged by the action of bleaching agents. Action of acid and alkali: It is unaffected by the action of acid and alkali. Action of organic solvent: Polyester textile is unaffected by organic solvent, hence polyester fiber could be dry-cleaned.

37. Polyester Molecular Structure Poly(ethylene terephthalater Fiber composed of linear macromolecules having in the chain at least 85% by mass of an ester of a diol & terephthalic acid.

38. Properties: Denier: 0.5 – 15 Tenacity : dry 3.5 - 7.0 : wet 3.5 - 7.0 Elongation at break : dry 15 - 45 : wet 15 45% Moisture Regain: 0.4 Specific Gravity: 1.36 - 1.41% Elastic Recovery : @2% =98 : @5% = 65 Melting point : 260 - 270 degree C Effect of Sunlight : turns yellow, retains 70 - 80 % tenacity at long exposure Resistance to Weathering: good Rot Resistance: high Alkali Resistance: damaged by CON alkali Acid Resistance: excellent Uses:  Pants  Shirts  Tops  Skirts  Suits  To manufacture high strength ropes  Thread, hoses,  Sails,  Floppy disk liners  Power belting

39. POLYESTER Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly  refers to polyethylene terephthalate (PET). Polyesters  include naturally occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics  through step-growth polymerization such as polycarbonate and polybutyrate.

40. Chemistry of Polyester Transesterification: An alcohol-terminate oligomer  and an ester-terminated oligomer condense to form  an ester linkage, with loss of an alcohol.   + + HOCH2CH2OH HOOC COOH HOCH2CH2OH Ethylene Glycol Terephthalic Acid HOCH2CH2OOC COOCH2CH2OH Bis(2-Hydroxyethyl) Terephthalate Polymerization + OC COOCH2CH2O HOCH2CH2OH n Polyester

42. Properties of Polyester -Normally tenacity varies from 4.5 to 5.0 gpd. -Extension at break varies from 20% to 30 %. -Polyester textile shows good resiliency property. -Very low moisture ranges from 0 – 0.4%. -It is not damaged by the action of bleaching agents. -It is unaffected by the action of acid and alkali. -Polyester fiber shows good dye ability at high temperature. -It is unaffected by the action of acid and alkali.