Question

The glass transition temperature of polyester is

• A. 80°C
• B. 100°C
• C. 210°C
• D. 230°C

Hint:

Remember that Tg is not the melting point. Tg represents a change in the amorphous regions of the polymer, whereas melting (Tm) applies to the crystalline regions. Polyester is a semi-crystalline polymer, meaning it has both amorphous and crystalline regions. Knowing typical Tg ranges for common polymers (PET, nylon, polypropylene) is helpful.

Answer 1

The Correct Option is A

Step 1: Understanding Glass Transition Temperature (Tg): The glass transition temperature (Tg) is the temperature at which an amorphous polymer transitions from a hard, glassy state to a more rubbery or flexible state. It's a crucial property for determining a polymer's processing and application temperatures. Different polymers have significantly different Tg values.
Step 2: Polyester's Tg: While the exact Tg of polyester can vary slightly depending on the specific type (e.g., PET, PBT) and its molecular weight, the most common type, polyethylene terephthalate (PET), has a Tg generally around 70-80°C. The other options are significantly higher and are more representative of melting temperatures (Tm) or degradation temperatures.