Polypropylene, V-ILINE150 for masks
18" wide, sold by the meter
Wash cold water, hang to dry, do not iron
I-LINE 150 is a 1.5 oz (lightweight) Polypropylene made from spun bonded fibers. The Spun Bond makes the product washable, but it still should only be washed in cold water and air-dried. No hot dryer. No direct IRON as it will melt. Use a drop/pressing cloth between the iron and the polypropylene.
Use it like interfacing between the two layers of cotton when making masks.
The reason this product is more effective than cotton has to do with how the fibers are arranged. In cotton you have a regular weave with threads crossing at 90-degree angles. This leaves a regular hole between the threads crossing. A spun fiber is irregular. Any particles have to travel around fibers to penetrate the polypropylene. That is less likely to happen as particles are trapped going round fibers.
There is also an electrostatic element to this fiber that 'holds' the particles (think static cling) and will not let them pass as easily. After washing, rub the mask against yourself to re-activate the static quality of the polypropylene.
The other type of polypropylene is melt blown. Melt blown is what the N95 and other disposable masks are made from. Think the blue and white masks.
The masks made from melt blown polypropylene CANNOT be washed as they are from single use polypropylene. They tend to be better at filtering droplets but again are not washable. If you have obtained melt blown polypropylene from some other source it can be used as a removable filter and thrown out with each use
No product is entirely effective so continue to keep your distance and wash your hands frequently. Make sure your mask always covers your nose and chin. An ill-fitting mask will never protect.