Very widely used polyester plastic. Often, PET is called “polyester” for short though there are numerous polyester groups. “Polyester fibre” textiles, in particular, are always made of PET. In addition to textile fibres, PET is used to manufacture plastic bottles for beverages as well as films. Because of the mass use of PET, the discarded material can be sorted into different types and largely be recycled for high-grade re-use. Almost 50% of the recycled material is turned into new plastic bottles, films or textile fibres. PET is semi-crystalline, the processing conditions defining the degree of crystallisation. If cooled down fast after moulding, the material is practically amorphous. This is the prerequisite for producing the glass-clear beverage bottles the customers are looking for. PET is polar and has a high surface tension. PET is closely related to PBT. The blend of the two polymers is likewise economically significant. By plasma coating, textiles made of PET are given a hydrophobic coat.