So, I had bought a ready meal (I have broken hand) enchilada, something I've never tried before. Instructions says 15 mins at 200c with plastic film lid, then take plastic film lid off and a further 15 mins at 200c. It came in a plastic tray. I never trust plastic so I took them out and put in some foil in a baking tray and that was big mistake as the underside fused to the foil. I got a mushy mess.
I have a silicone baking mat which I have never used. It says heat safe up to 250c on side of box. It seems ideal but I've yet to try it.
Best Answer
In general, your question is probably going to be labeled as health and opinion based and closed. It is very difficult to say something is safe-unsafe authoritatively because most such answers are opinion based as to who you are going to accept as authoritative. US FDA says they are safe. You will always find some group that says everything is unsafe. Taking a position in either direction ends up mostly unproductive, other than for things which have clearly been demonstrated as unsafe such as heating Teflon to very high temps.
That said, silicone mats are intended to be basically inert to most food contact to their recommended temperatures. Above that, they will start to break down and then all bets might be off. I personally assume they are safe, but would tend to avoid high acid items just for caution, but enchiladas would definitely not be high acid.