Polar fleece is a soft napped insulating fabric made from polyester. A soft, napped synthetic fabric with thermal insulation properties. Polar fleece (also called microfleece) is much lighter than wool but has some of the same properties as wool. It is soft, light, warm and comfortable. It resists water absorption (i.e. it is hydrophobic) and retains its thermal insulation even when wet. The fabric breathes well, also. However, it is quite flammable unless treated with a flame retardant, it is not windproof and it holds static electricity and hence accumulates lint, dirt and hair. It may also be prone to pilling.
Polar fleece originated in Massachusetts in 1979 when Malden Mills, (now Polartec LLC), and Patagonia developed Synchilla (synthetic chinchilla). It was a new, light, strong pile fabric meant to mimic—and in some ways surpass—wool. Aaron Feuerstein intentionally declined to patent Polar fleece, allowing the material to be produced cheaply and widely by many vendors, leading to the material’s quick and wide acceptance.