One material not to wear in an aviation environment is nylon.
In a fire it can cause major skin damage, as known and advised by the RAF. Even our aircrew watches which originally had a nylon strap, were suppiled with a leather "under strap" to protect the skin.
At least one major UK supplier of so called "flying clothing" (they provide free catalogues in aviation related magazines) sells 100% nylon copies of US military style nomex flying jackets. These are fashion items only and should be banned in aircraft, imho. In a previous job (helicopter SAR) I was provided with a similar one in blue, but I refused to wear it on safety grounds.
I was later justified after one of our crewman was burned whilst wearing one on a rescue job. Basically, it melted on him and began to shrink wrap him in scalding hot plastic. We got proper Nomex jackets after that.