Polyester is a durable synthetic fabric that does not stretch or shrink. Like other fabrics, polyester has bias stretch caused by the weaving process, but in garment production, pattern pieces are always cut on the non-stretching straight grain of the fabric.
Polyester is often mixed with other fibres to create fabric blends with characteristics more suitable for various applications an types of wear. A polyester stretch blend is produced by combining small amounts of Lycra or spandex, typically four or five percent, with polyester fibres. The addition of stretch to polyester garments improves comfort for the wearer by providing greater ease of movement.