Ethylene glycol and dimethyl terephthalate or terephthalic acid, petroleum by products.
Process:
The two chemicals ethylene glycol and terephthalic acid are combined in an autoclave which is like a huge pressure cooker. At high temperatures, both the chemicals react with each other and a polymer that contains about 80 to 100 repeating units is formed.
The polymer is extruded in a ribbon form which is removed and made into chips or pellets. Sometimes it can be stored in this form and shipped to the spinning mills.
The chips/pellets from different autoclaves are placed in a hopper and mixed to ensure uniformity.
The chips are made to fall on a hot grid which makes the polymer to melt.
The molten polymer is filtered to remove impurities and passed through a vacuum to suck the air bubbles which interfere in formation of continuous filament.
The purified polymer is forced through the holes of a spinnerette into cool air and then get solidified (melt spinning)
It is stretched or cold drawn to orient the molecules in the fibres in order to improve strength and fineness. The amount of drawing depends on the end uses of the fibre. Majority of the yarn produced will be utilized for production of textured yarns.
Generally polyester polymer is drawn 5 times their original length.
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