Polar fleece usually referred to simply as "fleece," is a soft napped insulating synthetic fabric made from Polyethylene terephthalate (PET) or other synthetic fibers. Other names for this fabric are "Polar Wool", "Vega Wool" or "Velo Wool", however the names of the composition suggests organic materials being used, fleece is 100% Polyethylene Terephthalate. One of the first forms was Polar Fleece created in 1979 by Malden Mills, now Polartec LLC., a new, light and strong pile fabric meant to mimic and in some ways surpass wool. Fleece has some of wool's finest qualities but weighs a fraction of the lightest available woollens.
Polar fleece is used in jackets, hats, sweaters, jogging bottoms/sweatpants, gym clothes, hoodies, inexpensive throw blankets, and high-performance outdoor clothing, and can be used as a vegan alternative to wool. It can be made partially from recycled plastic bottles and is very light, soft and easy to wash.
Fleece garments traditionally come in different thickness: micro, 100, 200, and 300, with 300 being the thickest and least flexible.
Advantages and disadvantages 
Fleece is a soft, lightweight, warm and comfortable fabric. It is hydrophobic, holding less than 1% of its weight in water, it retains much of its insulating powers even when wet, and it is highly breathable. These qualities make it useful for making clothing intended to be used during strenuous physical activity; perspiration is able to readily pass through the fabric. It is machine washable and dries quickly. It is a good alternative to wool (of particular importance to those who are allergic or sensitive to wool). It can also be made out of recycled PET bottles, or even recycled fleece.
There are disadvantages to this fabric as well. If not treated with a flame retardant, fleece is quite flammable, in contrast to wool, which is relatively nonflammable. Non-recycled fleece is made from non-renewable petroleum derivatives. Regular fleece is not windproof and does not absorb moisture (although this is often seen as a benefit, per above). Fleece also tends to generate a high amount of static electricity, which causes the accumulation of lint, dust, and pet hair. It is also susceptible to damage from high temperature washing, tumble drying or ironing. Lower-quality fleece material is also prone to pilling.
- Polar Fleece history and the history of pile fabrics
- "http://citizensforabetternorwood.blogspot.com/2009/03/xavier-hosting-aaron-feuerstein-on.html". Citizens For A Better Norwood. 2009-06-29.
- Rabbi Avi Shafran (2002-06-22). "Mr. Feuerstein is a legend in the corporate world. His company is now bankrupt and he doesn't regret a thing.".
- "Aaron Feuerstein". 2006-07-07.
- British Medical Journal: The Flammable Fabrics Problem
- Polartec Windpro web page
- Columbia Layering Guide for Warmth and Comfort by Frank Ross
- Choosing and Using a Quarter Sheet. Discussion of characteristics of wool vs. fleece
- Moisture Buffering
- Polartec, once Malden Mills, the original manufacturer of Polartec and Polarfleece
- How fleece is made (video)