For those making masks and using polypropylene (Oly-Fun and other non-woven fabrics):
If you try to iron this material, you will find it melts rather than just softening. To remove it from your iron’s soleplate, get a small can of Pro Strength Goof Off. It contains xylene which will dissolve polypropylene. The small can has a nice small spout which you can use to moisten a cotton swab and rub the stuck-on material from the sole plate. IF possible, do this outdoors and use nitrile gloves, as xylene and the other petroleum distillates in the Goof Off are both flammable and toxic.