Polyester fiber is one of most used fiber in the world which has variety of applications in many different fields. chemical base of this fiber is Polyethylene terephthalate and it has shown suitable thermal resistance. These fibers could be produced in two types of staple and filament. To produce polyester fiber, firstly, polymer melts in extruder chamber leading to spinneret to make polymer filament. Then, the hot filaments get through stretch zone and cooling zone respectively to get final fibers. If these filaments got cut by a cutter at the end of process line, staple fibers would be produced. It is possible to set the Length distance between two consecutive cut. To get more soft fibers, they are soaked in silicon oil in some cases.

Polyester fibers are made of two different sources, virgin material and recycled one which is cheaper and more cost-effective for some applications. However, the mechanical properties of virgin fibers are much better than recycled fibers.

China had been the biggest importer of recycled PET in the world and annually exported more than 1.5 million tons recycled fibers till 2018. After that, the production of staple polyester fiber was limited in the world in consequence of recycled PET import prohibition by China government. As a result of it, many countries aimed to start investing on fiber production to supply domestic and international demands.

These fibers could be hollow and solid depending on kinds of spinneret. What is more, these could be flat or conjugated. If fibers crimped during process the conjugated fibers which could be sharp, helical and waved would be created.

It should be mentioned that these fibers created thermal insulation due to presence of air between them so that it makes these fibers as a good option to use in clothes. Main purpose of using hollow fibers is related to reduction of material consuming and weight reduction to achieve more light-weight fiber.

These fibers are produced in many different deniers and length. If the denier would be about 1, the fiber would be known as microfibers.