Non-woven PP is made by taking polypropylene polymers and spinning them using heat and air into long fluffy threads, like cotton candy, then pressing the threads together between hot rollers to get a flexible but solid fabric with a weave-like texture similar to canvas. This fabric has been used for reusable bags for years and is now very popular for use as an extra layer in face masks.

click here for an interesting article on the use of this for masks…