A polyester, according to BISFA, is "a fibre composed of linear macromolecules having a chain at least 85% by mass of a diol and terephthalic acid". The first polyester was made in the UK in 1941. This polyester, known as polyethylene terephthalate (PET) has become by far the world's major man-made fibre. Other polyesters such as polybutylene terephthalate (PBT) and polytrimethylene terephthalate (PTT) are made but in much smaller quantities.
Polyester fibres are made in a very similar way to polyamide. Some plants take polyester polymer chips and melt them, at around 280 degrees C and then extrude the melt into continuous filaments to be wound onto packages or collected in cans as a tow before being stretched, crimped and cut into staple fibre. Other plants produce the polymer by a continuous process (CP) and form it into fibres without producing chips. A growing quantity is made by recycling PET bottles and other waste. If fully oriented yarns (FOY) are being produced the fibres are drawn on the spinning machine. If the yarn is to be textured, partially oriented yarns (POY) are spun.
Properties and End-Uses
Globally, polyester is by far the greatest man-made fibre. It is the workhorse for many, many applications because of its generally good properties at the lowest price. Apparel accounts for a large share of usage of polyester fibres or as blends. Industrial use, such as tyre cord fabrics, and unspun uses such as furniture fillings and nonwovens, are both expanding rapidly.