Two of the most common types of plastic are low-density and high-density polyethylene (LDPE and HDPE).
LDPE is cheap and flexible so is really common, especially for things like packaging. It also deforms near the boiling point of water. If you've had a bad experience like a plastic container melting in the dishwasher, or a soda bottle shriveling when filled with hot water, it was probably LDPE.
But there are other plastics like HDPE and polypropylene which are perfectly fine at 100°C. If you're using a plastic product designed for use with hot liquids (like nalgene or aeropress) it will be made of these materials.
I still felt nervous the first few times putting boiling water into a nalgene bottle...
LDPE is cheap and flexible so is really common, especially for things like packaging. It also deforms near the boiling point of water. If you've had a bad experience like a plastic container melting in the dishwasher, or a soda bottle shriveling when filled with hot water, it was probably LDPE.
But there are other plastics like HDPE and polypropylene which are perfectly fine at 100°C. If you're using a plastic product designed for use with hot liquids (like nalgene or aeropress) it will be made of these materials.
I still felt nervous the first few times putting boiling water into a nalgene bottle...