What is Polyester Fibre?
Polyester is one of the most important synthetic fibre made from a polymer called polyethylene terephthalate (PET). They are inexpensive, easily produced from petrochemical sources, and have a desirable range of physical properties. Polyester fibers are by far the most important textile raw material in terms of quantity. They are strong, lightweight, and wrinkle-resistant, having good wash–wear properties. Polyester, produced by the condensation polymerization of a dicarboxylic acid with a diol, contains in-chain ester units as their essential polymer-forming chain linkage.
Polyester is a long-chain polymer fibre derived from coal, water and petroleum. At least 85% of its weight consists of an ester plus dihydric alcohol and terephthalic acid. The fibre was developed during the Second World War, and the resultant fibre was called Terylene; the material was commercially manufactured in the United States by DuPont by 1951 and called Dacron. Since 1951, polyester has been developed and engineered to produce specific properties. There are two main varieties of polyester: polyethylene terephthalate (PET) and poly-1,4-cychlohexylene-dimethylene terephthalate (PCDT). PET is the most common type of polyester. At the time of this writing, polyester is used more commonly than any other fibre on the market.
Properties of Polyester Fibre:
Polyester fibre has several properties which make it a popular choice in the textile industry. It is strong and durable, resistant to wear and tear, and retains its shape well over time. Polyester is hydrophobic, but has a low absorbency rate and can wick away moisture. It is also resistant to shrinking and stretching, and has good thermal stability. Additionally, polyester is resistant to a wide range of chemicals and UV light, making it suitable for outdoor and industrial applications. However, polyester fibres tend to generate static electricity, which can be problematic in certain applications.
Here are some physical properties of polyester fibre:
| Property | Description |
| Melting point | 480 °C |
| Softening point | 460 °C |
| Modulus | 800–1000 cN / tex |
| Breaking strength | 40–60 cN / tex |
| Density | 1.38-1.40 g/cm3 |
| Tenacity | 3.0-8.0 g/den |
| Elongation | 15-45% |
| Moisture regain | 0.4-0.8% |
| Refractive index | 1.57-1.58 |
| Thermal conductivity | 0.12-0.17 W/mK |
| Specific heat capacity | 0.9-1.4 J/gK |
| Abrasion resistance | High but less compared to Nylon. |
| Thermal expansion coefficient | 2.5-5.5 × 10-5 K-1 |
| Hot air shrinkage | 3% at 100°C while shrinkage in boiling water is 6%. Shrinkage values are higher for high tenacity fibres. Heat stabilized crimped fibres give less than 1 % shrinkage in hot water. |
Here are some common properties of polyester fibre:
1. Strength: A strong fibre with good stability, but its performance can be further improved via a high-tenacity variation.
2. Resilience: Polyester has a high degree of resilience that prevents it from creasing because there is a fair amount of elasticity in the fibre.
3. Absorbency: Polyester is hydrophobic – in fact, it’s one of the least absorbent fibres – so it will dry quickly because moisture remains on the surface. This also means they will not stain easily.
4. Draping: The level of draping depends upon the variant of polyester. Filament yarns are satisfactory whereas trilobal are more supple therefore greater draping qualities. Spun polyester is flexible due to the spaces between the fibres and has a softer handle.
5. Insulating: Polyester that is textured, crimped or hollow provides good insulation.
6. Abrasion: Because it has high abrasion resistance, it can withstand excessive rubbing, wringing and scraping without breaking or any loss of strength.
7. Lightweight: The degree of its lightness varies based upon the denier of the fibre but it is still considered to be lightweight.
8. Resistance: Polyester will not shrink because it has been heat set during the production process; this fact makes the aftercare easier. It also has good resistance to light degradation, hence its suitability for outdoor wear. Polyester also resists insects, mildew, acids, most chemicals, perspiration and weak alkalis at room temperature but it becomes weaker when the temperature is increased. Similarly, its abrasion resistance is exceptional, being second to polyamide.
9. Susceptible: Filament polyester is round and has a smooth surface; thus, fabrics that are woven will have fewer spaces between the yarns to trap air for warmth. Although polyester is not absorbent, it does have an affinity for oil, which stains the fabric and is difficult to remove. Excessive heat causes polyester to melt, so care must be taken when using an iron even at a low temperature; although the stability of the fabric often negates the need for ironing. Spun polyester has a greater tendency to pill, so wash cycles should subject the material to minimal agitation.
Chemical properties of polyester fibre:
Strong acids and alkalies attack PET fibres and weaken them by hydrolysis. PET is resistant to normal laundering chemicals and is highly resistant to pest and microorganism attack. It is good insulator and have excellent heat setting properties.
Polyester Fibre Manufacturing Process:
The manufacturing process of polyester fibre is a complex and energy-intensive process that requires careful control of temperature, pressure, and other variables to produce high-quality fibres with consistent properties. Melt spinning is used to produce manufacture fibre.
Flow chart of polyester fibre manufacturing process:
PTA + EG + Catalyst -> PET Polymer
↓
Solidification (cooling) -> PET Chips
↓
Melt Spinning -> Continuous Filaments
↓
Drawing -> Stretched Filaments
↓
Crimping -> Staple Fibres
↓
Finishing -> Texturizing, Coating, Dyeing, etc.
↓
Final Product -> Polyester Fibre
The manufacturing process of polyester fibre generally involves the following steps:
1. Polymerization: The first step in producing polyester fiber is polymerization. This involves the reaction of ethylene glycol and terephthalic acid in the presence of a catalyst at high temperature and pressure. The resulting PET polymer is then cooled and cut into small pellets.
2. Melt spinning: The next step is to melt the PET chips and extrude them through spinnerets – small holes in a metal plate – to create continuous filaments. The filaments are then cooled by passing them through a chamber of air or water to solidify them.
3. Drawing: The filaments are then stretched or drawn to increase their strength and reduce their diameter. This process involves passing the filaments through a series of heated rollers, which pull the filaments at a controlled rate while they are still hot and pliable.
4. Crimping: To create staple fibres – short lengths of fibres used for textile applications – the continuous filaments are cut into shorter lengths and crimped to give them a wavy or zigzag shape. Crimping can be achieved by passing the fibres through a series of rollers or by using heated air or steam.
5. Finishing: The final step in the process is to apply any necessary finishes to the fibres, such as dyeing, coating, or texturizing. These finishes can enhance the fibres’ performance and appearance for specific applications.
Application / Uses of Polyester Fibre:
Polyester fibres are prospective in virtually all types of apparel end use either alone or in blends with cotton, wool, flax and other fibres. It offers elegant look and feel, wrinkle resistance, drip-dry character, wearing comfort and improved dimensional stability.
Polyester fibre is a versatile material that has a wide range of applications. Here are some of the most common applications of polyester fibre:
- Clothing and textiles: Shirts, pants, dresses, jackets, sportswear, outdoor clothing, curtains, bedspreads, upholstery, and carpets.
- Industrial and technical textiles: Conveyor belts, air filters, geotextiles, ropes, hoses, and inflatable structures.
- Packaging: Films, containers, bottles, and bags.
- Automotive: Car seats, upholstery, interior trim, and car covers.
- Outdoor applications: Awnings, tents, flags, banners, and sails.
- Home furnishings: Curtains, bedspreads, pillowcases, and furniture covers.
- Medical: Surgical sutures, implants, and medical fabrics.
- Sports and recreation: Backpacks, sports bags, and sports equipment.
- Construction: Insulation, roofing, and reinforcing fabrics.
- Electronics: Electrical insulation, electronic components, and cables.
- Toys and novelties: Stuffed animals, balloons, and inflatable toys.
- Personal care products: Diapers, feminine hygiene products, and wipes.
- Filtration: Air and water filtration systems.
- Agriculture: Crop protection, shade cloths, and insect nets.
- Fishing: Fishing nets and lines.
References:
- Fibres to Fabrics by Bev Ashford
- Textile Raw Materials By Ajay Jindal and Rakesh Jindal
- Textile Engineering – An Introduction Edited by Yasir Nawab
- Fibers: History, Production, Properties, Market by Dieter Veit
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