The glass transition (Tg) value of the following polymers: -[-S-]- CH3 -[-O-C-C-O-CO-]- CH3 -[N-CO-CO-N-O-]- PI, polyimide, PPS, polyphenylenesulfide, PC, polycarbonate, Which of the following is correct? a. PI > PC > PPS b. PPS > PC > PI c. PPS = PC > PI d. PI = PPS > PC
Answer (1)
The glass transition temperature (Tg) is an important property in polymers, marking the temperature range at which a polymer changes from a hard, glassy material to a soft, rubbery material. This is crucial for understanding the suitability of different polymers for various applications.
Let's look at the polymers involved:
Polyimide (PI): Polyimides are known for their high thermal stability and high glass transition temperatures. They are often used in applications requiring heat resistance.
Polycarbonate (PC): Polycarbonate is a durable polymer with a moderately high glass transition temperature. It is used in applications requiring good impact resistance and transparency, such as optical discs and eyewear.
Polyphenylene sulfide (PPS): PPS is a high-performance thermoplastic known for its high chemical resistance and a moderately high glass transition temperature that is typically lower than that of PI.
Given these characteristics and typical Tg values associated with these polymers, the correct order of Tg values should be:
PI generally has the highest Tg because of its thermal stability and application in high-temperature environments.
PC has a moderately high Tg but generally lower than PI.
PPS has a Tg lower than both PI and PC.
Thus, the correct answer is a. PI > PC > PPS.
This knowledge is important for engineers and scientists choosing materials for specific thermal environments, ensuring that the chosen polymer will perform satisfactorily below its Tg to maintain structural rigidity.
