PET polyethylene terephthalate sheets have a relatively good temperature resistance, but they do have limits when it comes to high temperatures. The specific temperature resistance of PET sheets can vary based on the manufacturing process, additives, and other factors. However, in general, PET sheets can withstand temperatures up to around 70 to 80 degrees Celsius (158 to 176 degrees Fahrenheit) without significant deformation or melting.

Here's a brief overview of the temperature resistance of PET sheets:

Low Temperatures: PET sheets remain stable and retain their properties at low temperatures, typically down to about -40 degrees Celsius (-40 degrees Fahrenheit).

Room Temperature: At room temperature (around 20 to 25 degrees Celsius or 68 to 77 degrees Fahrenheit), PET sheets are stable and can be easily used for various applications.

High Temperatures: PET sheets start to soften and deform when exposed to higher temperatures, generally around 70 to 80 degrees Celsius (158 to 176 degrees Fahrenheit). Above this temperature range, the material becomes less rigid and more susceptible to deformation.

Melting Point: The melting point of PET is approximately 250 degrees Celsius (482 degrees Fahrenheit). Beyond this temperature, PET sheets will begin to melt.

Because of their limited high-temperature resistance, PET sheets may not be suitable for applications that involve exposure to extreme heat or direct contact with hot surfaces. In environments where high-temperature resistance is critical, other materials like polycarbonate or polyimide may be more appropriate choices.