Let’s say you take the average American dryer and put it on hottest possible setting. There are a wide variety of plastics inside - plastic clothing tags, Ziploc bags, etc.
Would it be enough to soften or cause them to emit fumes?
Obviously this would be a dumb thing to do. But at what temperature does plastic start to soften?
Your average American clothes dryer reaches temperatures up around maybe 80deg C (175 deg F) or so, maybe a bit higher or lower depending on the model.
I found this on google, which may or may not be accurate:
The melting point of HDPE (High Density Polyethelyne) is about 130 ºC
The melting point of LDPE (Low Density Polyethelyne) is about 110 ºC
The melting point of PET (Polyethylene terphthalate) is about 250—260 ºC
The melting point of PP (Polypropylene) is about 160—170 ºC
The melting point of PS (Polystyrene) is about 70—115 ºC
The melting point of PVC (Polyvinyl Chloride) is about 75—90 ºC
A restricted vent can cause the temperatures to go much higher - The over temp cutout is 250°F:
My wife salvaged curbside sofa, covered with Herculon or some similar synthetic upholstery. She put the cushion covers in the laundromat and they melted.
Anecdotal, but when I was a kid, my mom accidentally ruined my sister’s and my winter coats by throwing them into the dryer on high. The zippers melted, because they were plastic. It was at the end of its life, though, so it might’ve been running too hot.
I once had a bunch of socks melt onto my other clothes in the dryer at a laundromat once. No idea how hot it was, and I’m sure it was WELL above normal operating temp.