New processing techniques that enhance polyester yarn performance
Polyester is the most commonly used synthetic fiber. It is made from petroleum and is used in a variety of products, including clothing, bottles, and boats. Polyester is made through a process called melt-spinning, which allows the fibers to be made in different shapes and sizes. Chemists can now alter the size and shape of polyester fibers to look and feel more like natural fibers.
Polyester fibers are formed through a chemical reaction between an acid and an alcohol. The two 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.
The first step-Polymerization
The process of making polyester fibers begins with polymerisation. 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.
The next step in the process is 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.
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.
Once the polyester yarn is drawn, it is wound on large bobbins or flat-wound packages, ready to be woven into the material.
Variations to polyester fibers
There are a number of different variations that can be made to polyester fibers. One variation is to add a delusterant, which makes the fiber dull or semi-dull. Another variation is to change 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.
Polyester fibers can also be drawn 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.
Polyester can also be dyed in a variety of colors. 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 is another variation that can be made to polyester fibers. 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.
Weaving into yarns
After the fiber itself is created, it is made into a yarn. There are two types of polyester yarns: filament and 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.
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.