The British scientists John Whinfield and James Dickson first invented polyester cloth in 1941 in England. After World War II was over, in 1945, the United States company DuPont bought the right to make polyester and by 1950 a factory in Delaware was beginning to actually make it.
People make polyester out of oil. You take the oil, which is a kind of very big hydrocarbon molecule, and break it down into two smaller molecules, ethylene glycol and dimethyl naphthalate, both still made entirely of oxygen, carbon, andhydrogen atoms. Dimethyl terephthalate is an ester, and ethylene glycol is a kind of alcohol. When you mix the ester and the alcohol together, they form molecules with both positive and negative charges, and the charges make the molecules line up in chains of crystals that hold together as long fibers.
The polymerized material comes out of the machine in long ribbons, and you cut the ribbons into little chips and let them harden. Then you melt the chips again and push the goo out through little holes to make thinner ribbons, and wind the thinner ribbons around spools. Then you heat the thinner ribbons and stretch them out to about five times their original length, to make them thin enough to use as thread to weave cloth.
Since the 1960s, polyester has been the cheapest kind of cloth, and almost half of all the world's clothing is made of polyester. You are probably familiar with polyester mainly from team shirts like for soccer or basketball.Polyester fiber is a " manufactured fiber in which the fiber forming substance is any long chain synthetic polymer composed at least 85% by weight of an ester of a dihydric alcohol (HOROH) and terephthalic acid (p-HOOC-C6H4COOH)" [3]. The most widely used polyester fiber is made from the linear polymer poly (ethylene terephtalate), and this polyester class is generally referred to simply as PET. High strength, high modulus, low _shrinkage, heat set stability, light fastness and chemical resistance account for the great versatility of PET.
These fibres are also known as Terylene, Terene, Dacron etc.
These fibres are synthetic textile fibres of high polymers which are obtained by esterification of dicarboxylic acids,
with glycols or by ester exchange reactions between dicarboxylic acid esters and glycols.
Thus Terylene is made by polymerising using ester exchange reation between dimethyl teraphthlate and ethylene glycol.
Raw Materials
The main raw materials required for the manufacture of Terylene polyester fibres are p-xylene ethylene glycol and methanol.or Dacron ( Du Pont ) is produced by polycondensation reaction using Teraphthaleic Acid (TPA) and Ethylene Glocol
Manufacture of TPA
P-xylene-- Air, nitric Acid-->P-Toluic Acid--> Teraphthaleic Acid
Manufacture of DMT
p-xylene--Air 200 degC, co-toluate--> Toluic Acid--Ch3OH--> Monomethyl toluate--oxidation--> Monomethyl teraphthalate--CH3OH--> DMT
The use of Dimethyl Teraphthalate is preferred instead of Teraphthalic acid as the purity of the reacting chemicals is essential and it is easier to purify DMT than teraphthalic acid.
Manufacture of Ethylene Glycol
Ethylene--Oxidation with air-->Ethylene Oxide--Hydrolysis-->Ethylene Glycol
or
Ethylene--Hypochlorous Acid HOCl--> Ethylene Chlorohydrin--Alkaline Hydrolysis--> Ethylene Glycol
Production
The polymer is made by heating teraphthalic acid with excess of ethylene glycol ( Both of high priority) in an atmosphere of nitrogen initially at atmospheric pressure. A catalyst like Hydrochloric acid speeds up the reaction.
The resulting low molecular weight ethylene glycol teraphthalate is then heated at 280 deg C for 30 minutes at atmospheric pressure and then for 10 hours under vacuum. The excess of ethylene glycol is distilled off. the ester can polymerise now to form a product of high molecular weight. The resulting polymer is hard and almost white substance, melting at 256 deg C and has a molecular weight of 8000-10000. Filaments are prepared from this.
Spinning of Polyester Fibres
The polymer is extruded in the form of a ribbon. This ribbon is then converted into chips.The wet chips are dried and fed through a hopper, ready for melting. This molten polymer is then extruded under high pressure through spinnerettes down to cylinder.
Each spinnerette contains 24 or so holes. A spinning finish is applied at this stage as a lubricant and an antistatic agent. The undrawn yarn is then wound onto cylinders.This yarn goes to the drawing zone, where draw twist machines draw it to about four times their original length. This is hot drawn in contrast to cold drawing of nylon filaments.
For the production of staple fibres, the filaments are first brought together to from a thick tow. These are distributed in large cans. The tow is drawn to get correct strength. Then it is passed through a crimping machines, the crimps being stabilized by heating in ovens. It is then cut into specified lengths and baled ready for dispatch.
Properties of Polyester
| Tenacity (gpd) | High Tenacity | Normal Tenacity | Staple |
| Dry | 6-7 | 4.5-5.5 | 3.5-4 |
| Wet | 6-7 | 4.5-5.5 | 3.5-4 |
| Elongation (%) | |||
| Dry | 12.5-7.5 | 25-15 | 40-25 |
| Wet | 12.5-7.5 | 25-15 | 40-25 |
| Density | 1.38 | 1.38 | 1.38 |
Moisture RegainAt 65% RH and 70 deg F--> 0.4%Because of low moisture regain, it develops static charge. Garments of polyester fibres get soiled easily during wear.
Thermal Properties
Polyester fibres are most thermally stable of all synthetic fibres. As with all thermoplastic fibres, its tenacity decreases and elongation increases with rise in temperature. When ignited, polyester fibre burns with difficulty.
Shrinkage
Polyester shrinks approx 7% when immersed in an unrestrained state in boiling water. Like other textile fibres, polyester fibres undergo degradation when exposed to sunlight.
Its biological resistance is good as it is not a nutrient for microorganisms.
Swelling and Dissolving
The fibre swells in 2% solution of benzoic acid salycylic acid and phenol.
Alcohols, Ketones, soaps, detergents and drycleaning solvents have no chemical action on polyester fibres.
Chemical Resistance
Polyester fibres have a high resistance to organic and mineral acids. Weak acids do not harm even at boil. Similarly strong acids including hydrofluoric acids do not attack the fibres appreciably in the cold.
CHEMICAL PROPERTIES
Polyester fibers have good resistance to weak mineral acids, even at boiling temperature, and to most strong acids at room temperature, but are dissolved with partial decomposition by concentrated sulfuric acid. Hydrolysis is highly dependent on temperature. Thus conventional PET fibers soaked in water at 70oC for several weeks do not show a measurable loss in strength, but after one week at 100oC, the strength is reduced by approximately 20%.
Polyesters are highly sensitive to bases such as sodium hydroxide and methylamine, which serve as catalysts in the hydrolysis reaction. Methylamine penetrates the structure initially through noncrystalline regions, causing the degradation of the ester linkages and, thereby, loss in physical properties. This susceptibility to alkaline attack is sometimes used to modify the fabric aesthetics during the finishing process. The porous structures produced on the fiber surface by this technique contribute to higher wettability and better wear properties [7].
Polyester displays excellent resistance to oxidizing agents, such as conventional textile bleaches, and is resistant to cleaning solvents and surfactants. Also, PET is insoluble in most solvents except for some polyhalogenated acetic acids and phenols. Concentrated solutions of benzoic acid and o-phenylphenol have a swelling effect.
PET is both hydrophobic and oleophilic. The hydrophobic nature imparts water repellency and rapid drying. But because of the oleophilic property, removal of oil stains is difficult. Under normal conditions, polyester fibers have a low moisture regain of around 0.4%, which contributes to good electrical insulating properties even at high temperatures. The tensile properties of the wet fiber are similar to those of dry fiber. The low moisture content, however, can lead to static problems that affect fabric processing and soiling.
OPTICAL PROPERTIES
Polyester fibres are most thermally stable of all synthetic fibres. As with all thermoplastic fibres, its tenacity decreases and elongation increases with rise in temperature. When ignited, polyester fibre burns with difficulty.
Shrinkage
Polyester shrinks approx 7% when immersed in an unrestrained state in boiling water. Like other textile fibres, polyester fibres undergo degradation when exposed to sunlight.
Its biological resistance is good as it is not a nutrient for microorganisms.
Swelling and Dissolving
The fibre swells in 2% solution of benzoic acid salycylic acid and phenol.
Alcohols, Ketones, soaps, detergents and drycleaning solvents have no chemical action on polyester fibres.
Chemical Resistance
Polyester fibres have a high resistance to organic and mineral acids. Weak acids do not harm even at boil. Similarly strong acids including hydrofluoric acids do not attack the fibres appreciably in the cold.
CHEMICAL PROPERTIES
Polyester fibers have good resistance to weak mineral acids, even at boiling temperature, and to most strong acids at room temperature, but are dissolved with partial decomposition by concentrated sulfuric acid. Hydrolysis is highly dependent on temperature. Thus conventional PET fibers soaked in water at 70oC for several weeks do not show a measurable loss in strength, but after one week at 100oC, the strength is reduced by approximately 20%.
Polyesters are highly sensitive to bases such as sodium hydroxide and methylamine, which serve as catalysts in the hydrolysis reaction. Methylamine penetrates the structure initially through noncrystalline regions, causing the degradation of the ester linkages and, thereby, loss in physical properties. This susceptibility to alkaline attack is sometimes used to modify the fabric aesthetics during the finishing process. The porous structures produced on the fiber surface by this technique contribute to higher wettability and better wear properties [7].
Polyester displays excellent resistance to oxidizing agents, such as conventional textile bleaches, and is resistant to cleaning solvents and surfactants. Also, PET is insoluble in most solvents except for some polyhalogenated acetic acids and phenols. Concentrated solutions of benzoic acid and o-phenylphenol have a swelling effect.
PET is both hydrophobic and oleophilic. The hydrophobic nature imparts water repellency and rapid drying. But because of the oleophilic property, removal of oil stains is difficult. Under normal conditions, polyester fibers have a low moisture regain of around 0.4%, which contributes to good electrical insulating properties even at high temperatures. The tensile properties of the wet fiber are similar to those of dry fiber. The low moisture content, however, can lead to static problems that affect fabric processing and soiling.
OPTICAL PROPERTIES
PET has optical characteristics of many thermoplastics, providing bright, shiny effects desirable for some end uses, such as silk-like apparel. Recently developed polyester microfiber with a linear density of less than 1.0 denier per filament (dpf), achieves the feel and luster of natural silk [23].
THERMAL PROPERTIES
The thermal properties of PET fibers depend on the method of manufacture. The DTA (Fig. 5.) and TMA (Fig. 6) data for fibers spun at different speeds show peaks corresponding to glass transition, crystallization, and melting regions. Their contours depend on the amorphous and crystalline content. The curves shown for 600 m/min and above are characteristic of drawn fiber. The glass transition range is usually in the range of 75oC; crystallization and melting ranges are around 130oC and 260oC, respectively.
Uses of Polyester
1. Woven and Knitted Fabrics, especially blends.
2. Conveyor belts, tyre cords, tarpaulines etc.
3. For filling pillows
4. For paper making machine
5. Insulating tapes
6. Hose pipe with rubber or PVC
7. Ropes, fish netting and sail cloth.
1. Woven and Knitted Fabrics, especially blends.
2. Conveyor belts, tyre cords, tarpaulines etc.
3. For filling pillows
4. For paper making machine
5. Insulating tapes
6. Hose pipe with rubber or PVC
7. Ropes, fish netting and sail cloth.