When hot water is placed into an empty water bottle, the bottle keeps its shape and does not soften. What type of plastic is the water bottle made from?

Thermoset, or thermosetting, plastics are synthetic materials that strengthen during being heated, but cannot be successfully remouldedor reheated after their initial heat-forming. This contrasts withthermoplastics, which soften when heated and harden and strengthen after cooling. Thermoplastics can be heated, shaped and cooled as often as necessary without causing a chemical change, while thermosetting plastics will burn when heated after the initial moulding.