Triexta is the shorthand label given to polytrimethylene terephthalate (PTT), a thermoplastic fiber and subclass of polyester used in textiles and carpet. Triexta fibers combine the properties of both nylon and polyester, giving it resiliency and elasticity along with lightfastness, abrasion resistance, and tensile strength. It mimics the soft hand of wool and is naturally hydrophobic, making it inherently stain- and mildew-resistant without the use of additives. The fiber dyes well and is also naturally static-resistant and easily blended with other fibers. Triexta is available in two fiber versions, one that is petroleum-based and another by DuPont Sorona that is made of up to 37-percent bio-based ingredients.