How does the Glass Transition Temperature (Tg) of polymers influence their use in high-temperature applications?

The glass transition temperature (Tg) marks the point where a polymer changes from a stiff, glassy state to a more rubbery, flexible state; if a polymer’s Tg is below the operating temperature, it will soften and lose mechanical strength. In high‑temperature applications, engineers select polymers whose Tg is well above the service temperature to keep the material rigid and stable. For example, a polymer with a Tg of 150 °C will remain solid in a 100 °C environment, whereas a polymer with a Tg of 80 °C will become pliable and fail. Thus, knowing Tg lets designers predict whether a polymer will maintain its shape and load‑bearing ability under heat, guiding material choice for components like seals, gears, or heat‑shielding parts.