Polyester is a synthetic fiber made of polyester material, most of which is 85% thermoplastic. It is a type of artificial fiber used as a fabric raw material in textiles. The abbreviation for polyester is PES.
Polyester is one of the world’s most popular textile raw materials and is used in thousands of different consumer and industrial applications. The word polyester refers to fabric that is usually made of polyester fiber. Polyester fibers are often used together with cotton fibers to produce garments with better properties.
Polyester fabric has found a wide area of use in textiles. A wide variety of knitted and woven fabrics such as taffeta, single jersey, rib, organza and satin are produced from polyester yarn, which can be used alone or mixed with other fibers.
Chemically, polyester is a polymer composed primarily of compounds within the ester functional group. Polyester is a category of polymers, or more specifically, condensation polymers containing ester functional groups within their main bond. Polyester generally refers to a large family of synthetic polyesters that includes all polyethylene terephthalate and polycarbonate.
Polyester fibers, which are mostly mixed with cotton fiber, can also be used with wool, acrylic, silk, viscose and linen fibers. Polyester fibers produced with the trade names Terylene and Trevira in England, Dacron in the USA, and Diolen in Germany are the most widely used synthetic fibers today.
It is a fiber that is easy to obtain and has properties close to natural fibers. It is an artificial fiber that has the closest properties to cotton, and polyester fibers have come to the fore with the increasing need for cotton.
The polyester obtained as a result of the condensation of a dialkol and dicarboxylic acid is examined in 3 groups in terms of its chemical structure.
1. Group PET (polyethylene terephthalate) fibers
2. Group PCDT (poly-1.4 cyclohexyl-dimethylene-terephthalate) fibers
3. Group Modified polyester fibers
How is polyester fabric made?
Polyester fibers are obtained by two methods. In the first, ethylene glycol and dimethyl terephthalate are taken as starting materials. In the second method, ethylene glycol and terephthalic acid are taken as the starting material. The polymerized raw material is taken by cooling in the polymerization vessel and produced by cutting into small pieces. The polymers are melted at a melting point of 260 °C and turned into filaments by soft spinning. These filaments are then subjected to a stretching process to increase their strength.
The production of polyester fiber is obtained from the polyethylene terephthalate (PET), which is obtained from the petroleum industry, and the polytetramethylene terephthalate (PTMT) polymer, which is produced in limited quantities only for very special uses, by melt production technique. PET yarn can be produced as filament or staple fiber of various lengths and fines. The fineness and length of the fiber to be produced are determined according to whether the fiber will be processed with cotton or wool, or whether it will be silk-like or cotton-like or in a different manner. The filament yarn or tow is pulled to orient the molecules and increase fiber strength. Staple fibers are curled. Because they are light and provide good insulation, hollow filaments are used as filling fibers in quilts, sleeping bags and parkas.
The difference between PET and PTMT
PTMT has a lower melting temperature and is easier to dye than PET. It can be used as a textured yarn in stretch jeans and as a PET/PTMT composition yarn in clothing and thin pantyhose, as they create bulk and stretch due to different shrinkage. Standard polyester has good elongation resistance and this gives it a distinctive handle, anti-wrinkle and good dimensional stability in use.
Since polyester does not easily stretch at low loads, it is not suitable for pantyhose and tights, but PTMT is more successful in these applications. PET has good resistance to abrasion, but when used with blends, if a special fiber or a special finishing treatment is not applied, the formation of static electricity charges is explained by the low moisture absorption of the fiber. It is used in sewing threads as polyester staple fibers and filaments. The fiber is resistant to degradation by ultraviolet rays. The thermoplastic property of the fiber contributes to the crimp stability of the fiber and the dimensional fixation achieved by heat treatment in fabrics.
With air-jet and false twist texturing techniques, filament yarns are folded to improve handle, bulkiness and elastic rebound properties. Depending on the level of flexibility created, textured polyester yarns are used in sportswear, Appropriately selected polyester fiber is used in protective clothing, sails, filter fabric and car roof covering. It is used for functional and industrial purposes, including soft composites used in car bodywork and hard composites used in car bodywork.
Physical properties of polyester fibers
Cross-section and longitudinal view: Polyester fibers appear as a smooth rod under the microscope. Its cross section is round.
Color: Polyester fibers are generally produced in white. Polyester fiber is bright, if desired, they can be obtained as semi-matt or matte.
Fineness and length: Polyester fibers can be produced in various lengths. Depending on the area of use, it can be in the form of filaments or in the form of staples.
Strength: The strength of polyester fibers varies according to the production method. The strength of polyester fibers in filament is between 4-7 gr/denier.
Moisture absorption: Polyester fibers have very low moisture absorption properties. This rate varies between 0.2-0.8% under normal conditions. Since polyester fibers can hold moisture on the surface without absorbing them, it is ensured that the products with polyester fabric can be worn in hot weather.
Resistance to friction: The resistance of polyester fibers to friction is very good. Pitting problems may be encountered in some fabrics.
Dimensional stability: The polyester fibers, which are hot-fixed, have very good dimensional stability. Hot-fixed polyester fabrics can shrink at high temperatures.
Flexibility and springiness: Polyester fibers generally have good flexibility and springiness. The elongation rate of polyester fibers in filament varies between 15-30% and 30-50% in staple form.
Volumetric density: Polyester fibers are a light fiber, with a specific weight of 1.38 gr/cm³.
Chemical properties of polyester fibers
Affected by chemicals: Polyester fibers are resistant to acids, solvents used in dry cleaning and bleaches. Strong alkalis damage the fibers.
Resistance to environmental factors: The resistance of polyester fibers to sunlight is better than many synthetic fibers. Prolonged exposure to sunlight can damage the fibers. It can be used as curtain fabric. Bacteria, fungi, mold, moths and other harmful insects do not damage the fibers.
Electrifying property: Since the electrical conductivity of polyester fibers is very low, they are charged with static electricity.
Ability to be affected by heat: The melting point of polyester fibers is 250 °C. Since polyester products do not wrinkle much, it is necessary to iron them at low temperatures and for short periods of time. The ironing temperature is 140 °C.
Combustion property: When polyester fibers meet with flame, they melt by pulling. It leaves a chemical smell and a black soot. The ash is cream-colored, bead-shaped and hard.