As someone who has experienced the pain of "getting melted plastic picked out of skin", wear cotton when doing anything involving flame. Unless you can get NOMEX, then wear that.
I had a 80/20 polyester/cotton sweatshirt on and it caught on fire when I was welding on a semi truck. It melted into my chest. 14 years later I still have places hair don't grow and a couple scars from it. And I put it out quickly, with a cotton shirt on under it.
Being a screaming Alpha is not fun. Never want to repeat that again.