The polyester known as "PET" (polyethylene terephthalate) is used in carpet manufacturing in both spun and filament constructions. After the price of raw materials for many types of carpet rose in the early 2000s, polyester became more competitive.
Polyester has good physical properties and is inherently stain-resistant because it is hydrophobic, and, unlike nylon, does not have dye sites. Colour is infused in a molten state (solution dyeing). Polyester has the disadvantage that it tends to crush or mat down easily. It is typically used in mid- to low-priced polyester.