Polyester Fiber
Preparation of Monomers, PET and manufacturing process
Polyester Fiber
Polyesters have hydrocarbon backbones characterized by the presence of carboxylate ester groups distributed either regularly or randomly along the main polymer chain. On the other word, Polyesters are those fibers containing at least 85% of a polymeric ester of a substituted aromatic carboxylic acid including but not restricted to terephthalic acid and f-hydroxybenzoic acid. The major polyester in commerce is polyethylene terephthalate, an ester formed by step growth polymerization of terephthalic acid and the diol ethylene glycol.
Polyethylene terephthalate polyester is the leading man-made fiber in production volume and owes its popularity to its versatility alone or as a blended fiber in textile structures. When the term “polyester” is used, it refers to this generic type.
Most widely used PET fiber is made from the linear polymer (polyethylene terephthalate), which is synthesized by reacting ethylene glycol (HOCH₂-CH₂OH) with either terephthalic acid or its methyl ester in presence of an antimony catalyst.
This fiber is enjoying world-wide production and are marketed under a variety of trade names such as Terylene (ICI), Dacron (Du Pont), Trevira (Hoechst), Kodel II (Eastman) etc. Among all manufactured polyester fibers, Terylene and Dacron have the more commercial. It is used extensively in woven and knitted apparel, home furnishings, and industrial applications. Modification of the molecular structure of the fiber through texturizing and or chemical finishing extends its usefulness in various applications. Polyester is expected to surpass cotton as the major commodity fiber in the future.
Next to PET fiber, PBT (Polybutylene terephthalate) fibers are somewhat commercially important. But they are produced to a limited extent due to their some limitations both in physical and chemical aspects.
Preparation of Monomers
EG used for the synthesis of poly(ethylene terephthalate) is a clear and purified liquid. It should be free from color impurities and traces of strong acids and bases. It can be derived in different ways.
Ethylene glycol can also be produced from earth oil. The oil is cracked to give ethylene, which is catalytically oxidized with air to ethylene oxide followed by acid hydrolysis.
Ethylene Glycol, this is made by the catalytic oxidation of ethylene, which is obtained from petroleum cracking. Ethylene oxide is produced (1). Hydration of this yield’s ethylene glycol (2).
Para-xylene is obtained from petroleum is oxidized (3), for example with nitric acid or with air in the presence of a catalyst. Terephthalic acid is esterified with methyl alcohol (4) to form dimethyl terephthalate.
Preparation of PET(Polyethylene terephthalate)
Manufacturing of Polyester Fiber/(How Polyester Fiber is made?)
Polymerization
Drying
Melt spinning
Drawing the fiber
Winding
Polymerization
To form polyester, dimethyl terephthalate is first reacted with ethylene glycol in the presence of a catalyst at a temperature of 302–410°F (150–210°C).
The resulting chemical, a monomer (single, non-repeating molecule) alcohol, is combined with terephthalic acid and raised to a temperature of 472°F (280°C). Newly-formed polyester, which is clear and molten, is extruded through a slot to form long ribbons.
Drying
After the polyester emerges from polymerization, the long molten ribbons are allowed to cool until they become brittle. The material is cut into tiny chips and completely dried to prevent irregularities in consistency.
Melt spinning
Polymer chips are melted at 500-518°F (260-270°C) to form a syrup-like solution. The solution is put in a metal container called a spinneret and forced through its tiny holes, which are usually round, but may be pentagonal or any other shape to produce special fibers. The number of holes in the spinneret determines the size of the yarn, as the emerging fibers are brought together to form a single strand.
At the spinning stage, other chemicals may be added to the solution to make the resulting material flame retardant, antistatic, or easier to dye.
Drawing the fiber
When polyester emerges from the spinneret, it is soft and easily elongated up to five times its original length. This increases the strength, tenacity, and resilience of the fiber. This time, when the filaments dry, the fibers become solid and strong instead of brittle.
Drawn fibers may vary greatly in diameter and length. Also, as the fibers are drawn, they may be textured or twisted to create softer or duller fabrics.
Winding
After the polyester yarn is drawn, it is wound on large bobbins or flat-wound packages, ready to be woven into material.
Are Polyester Fiber Pillow being safe? (Can Polyester Fiber be washed?)
A pillow is a high-loft product that is usually made from a textile fabric shell and a filling material: natural or polyurethane foam, down/feathers, textile fibers, non-textile materials, such as buckwheat husk, etc. The main function of a pillow is to support the human neck and head in a position that maintains the cervical spine in its neutral position while sleeping.
Currently, the most commonly used fiber filling material in high-loft articles, including pillows, is PET (Polyethylene terephthalate), due to its good washability properties, bulkiness, resilience, availability and low price.
In terms of moisture management, PET fibers are not an optimal filling material for pillows, as they do not absorb perspiration. On the contrary, PET fibers typically retain moisture on the fiber surface and fill the pores between fibers. When moisture replaces the air in pores, it causes a decrease in thermal resistance, and gives an unpleasant cool and wet feeling in contact with the human skin. “Considering everything, PET pillows are safe but may not be comfortable for long-term use.”
