Polyester Fiber and its uses

Introduction to Polyester

Polyester is a chemical term that can be broken into poly, meaning many, an ester, a basic organic chemical compound. Polyester is a term often defined as “long-chain polymers chemically composed of at least 85% by weight of an ester and a dihydric alcohol and a terephthalic acid”. In other words, it means the linking of several esters within the fibers. Polyester is a synthetic fiber derived from coal, air, water, and petroleum.

Developed in a 20th-century laboratory, polyester fibers are formed from a chemical reaction between an acid and alcohol. In this reaction, two or more molecules combine to make a large molecule whose structure repeats throughout its length. Polyester fibers can form very long molecules that are very stable and strong.

Polyester is used in the manufacture of many products, including clothing, home furnishings, industrial fabrics, computer and recording tapes, and electrical insulation. Polyester has several advantages over traditional fabrics such as cotton.

Today, polyester is largely regarded as a cheap fabric that is rather uncomfortable for sensitive human skin to wear.

However, with the emergence of luxury fibers like polyester microfiber and various polyester blends the industry is experiencing a resurgence. The Tennessee Eastman Company and the Man-Made Fiber Producers’ Association’s (MMFPA) Polyester Fashion Council played a significant role in the revival of polyester. The Tennessee Eastman Company started a YES campaign for polYESter and popularized it via radio and television. The idea was to focus on the wash-and-go properties of polyester rather than sell it as a cheap fabric.

Today, the biggest contributor to the appeal of polyester is the discovery of microfibers. Microfibers give polyester the feel of silk and are rapidly becoming the choice of fabric. With an expensive tag to match, the cheap image of polyester seems to be on its way out. Here’s to heralding a new era in the history of polyester!

History of Polyester

In 1926, United States-based E.I. du Pont de Nemours and Co. began research into very large molecules and synthetic fibers. This early research, headed by W.H. Carothers, centered on what became nylon, the first synthetic fiber

Soon after, in the years 1939-41, British research chemists took interest in the du Pont studies and conducted their own research in the laboratories of Calico Printers Association Ltd. This work resulted in the creation of the polyester fiber known in England as Terylene.

In 1946, du Pont purchased the right to produce this polyester fiber in the United States. The company conducted some further developmental work, and in 1951, began to market the fiber under the name Dacron. During the ensuing years, several companies became interested in polyester fibers and produced their own versions of the product for different uses.

Subsequent to the development of Terylene and Dacron, Kodel was developed by Eastman Chemical Products, Inc in 1958. The polyester market underwent rapid expansion and textile mills emerged everywhere. Many of the mills were located at small gas stations and produced cheap polyester apparel. The inexpensive and durable fiber became very popular and the industry expanded rapidly till the 1970s. Unfortunately, the infamous double-knit polyester image hit the industry and polyester soon came to be known as the uncomfortable fabric.

• Polyester is the most used synthetic fiber.
• The fiber can be manufactured in different shapes and sizes for specific purposes.
• Polyester is a tough fabric used in clothing

Polyester Manufacturing Process

Polyester is the most commonly used synthetic fiber. DuPont introduced its Dacron brand of polyester in 1951, but the material itself was patented earlier in 1941.

It’s made by reacting dicarboxylic acid with dihydric alcohol. This base material can be used to make many things, from soda bottles to boats, as well as clothing fibers. Like nylon, polyester is melt-spun – this process allows the fibers to be made in different shapes and sizes for specific applications. Chemists can now alter the size and shape of polyester fibers to look and feel more like natural fibers. Ultra-thin microfibers can give polyester a smoother, softer feel than the polyester of twenty years ago.

Polyester fibers, the synthetic fibers, are long-chain polymers derived from coal, air, water, and petroleum. They are formed through a chemical reaction between an acid and alcohol. In this reaction, two or more molecules combine to make a large molecule whose structure repeats throughout its length. These molecules are very stable and strong. There are variations in the compositions and therefore in the properties of polyester fibers.

Polymerization

Condensation polymerization occurs when the acid and alcohol are reacted in a vacuum at high temperatures. The polymerized material is extruded in the form of a ribbon onto a casting trough or cooling wheel. After the ribbon hardens, it is cut into chips.

Spinning

Polymer chips are melted at 500-518°F (260-270°C) to form a syrup-like solution. The molten polymer is then extruded through a spinneret and the filaments are subsequently drawn into the desired polyester fiber. Variations are introduced to obtain desired end results.

 

Spinnerets having holes of different shapes such as round, trilobal, pentalobal, hexalobal or octalobal can be used for special effects like opacity, luster or its suppression, wicking, comfort or feel. Hollow fibers may be produced to make it lightweight and for providing greater cushioning or insulative properties. Crepe effect can be obtained through crimps. Certain additives may also be combined with the spinning solutions for specific properties. Delusterant can be added to make the fiber dull, a flame retardant may be added or certain other antistatic substances may also be included.

Drawing

After extrusion from the spinneret, the fibers are drawn or elongated, with the help of godet wheels. Depending upon the desired properties, the polyester fibers are usually drawn up to five times their original length. For higher tenacity, the filaments are drawn to a greater extent. When the fibers come in contact with the air, they solidify.

Usually, the PET fibers are drawn hot as it produces more uniform fibers. PCDT fibers are drawn at higher temperatures due to their higher melting point. During the drawing process itself, fibers may be textured which saves time, effort, and production cost and also gives greater quality control over the finished fibers. After the polyester yarn is drawn, it is wound on large bobbins or flat-wound packages, ready to be woven into the material.

Variations on the Basic Polyester

Different fibers can be created by doing one or more of the following:

• Adding a delusterant: Polyester is a naturally bright fiber, but can be made dull or semi-dull by the addition of a delusterant.
• Changing the shape of the spinneret: The simplest and most common shape is a circle, but by changing the shape of the spinneret, square, oval, and bean-shaped fibers can be formed. One can even create a hollow fiber. The different shapes affect the hand and strength of the fiber.
• Drawing it out more: Drawing out the fiber to five times its original length is normal, but polyester can be stretched even further to create the now-popular microfiber. Drawing it out may also affect strength, elasticity, and dyeability.
• Adding dye: In its natural state, polyester is a slightly transparent off-white. Adding dye at the manufacturing stage can create brilliant colors like electric blue and atomic red.
• Crimping: When the fiber is drawn out it is long and smooth. Crimping can give the fiber more texture and bulk and can increase its insulation properties, as well as its elasticity

Making Yarns

After the fiber itself is created, it is made into a yarn. There are two types of polyester yarns:

1. filament
2. spun

Filament yarns are made by taking the long polyester filaments, grouping them together, and then twisting them to make them thicker and stronger. A monofilament yarn has just one, long polyester fiber that is not twisted.

Spun yarns are produced in much the same way that cotton or wool yarn is produced. The long filaments are fist cut into short pieces called staples. These are then combined together and spun to create a yarn made up of thousands of short filaments.

Blends

At this stage, polyester can also be combined with other fibers to produce a variety of effects.

Polyester and cotton are probably the most famous and popular blends. The polyester helps the fabric retain its shape and resist stains and wrinkles. The cotton makes the fabric more absorbent and comfortable.

Polyester is combined with wool to give it wrinkle-resistance and shape retention in all kinds of weather. Since polyester is stronger than wool, it increases the durability and life of the fabric. The wool contributes good draping characteristics and elasticity.

Polyester and rayon are other popular blend fabrics. Here again, the polyester makes the fabric more resilient and durable and helps it keep its shape. The rayon adds a different texture, has a good hand, is good for draping, and is absorbent.

Polyester and nylon produce a strong fabric because of nylon’s strength and abrasion resistance and polyester’s wrinkle-free properties. This combination produces a yarn that is strong, durable, stable, easy to launder, and resistant to mildew and insects. Problems with this blend, however, are that pilling may occur, and it does not have a very good hand. Furthermore, since neither nylon nor polyester is very absorbent, the fabric may feel wet and clammy in warm or humid weather.

Weaving

After the yarns are made, they are shipped out to textile mills to be woven into fabric. Polyester can be made into both woven and knitted fabrics (such as the infamous double-knit!)

Finishing Processes

Finally, after the fabric is made, one or more of the following finishing processes is often used to improve the quality of the fabric:

• Heat setting–creates a permanent shape
• Singeing–improves the hand, reduces pilling, and increases the smoothness
• Anti-static finish–reduces static electricity
• Water and stain repellency–increases comfort and makes it easier to clean; also used for rainwear
• Resin finishes–increases ease of care
• Calendering–increases smoothness and reduces pilling
• Embossing–creates a design and/or luster