Polyester elastic is the least expensive and most versatile elastic thus making it the most popular fiber sold. It is widely used in the medical industry and for most wash and wear fabrics. Probably because of its versatility and durability, polyester is the standard fiber used for all 3 different types of flat elastics- braided elastic, knitted elastic and woven elastic. Polyester elastic is not prone to shrinkage and has an excellent resistance to mildew and bleach. While the material wont begin to melt until it reaches 450 degrees, the fibers will start to weaken and lose strength with prolonged exposure to sun.