Question

Binary polymer blends of polypropylene and polyamide 6 are immiscible. From a thermodynamic viewpoint this is due to \(\underline{\hspace{2cm}}\).

• A. low enthalpy of mixing
• B. high entropy of mixing
• C. high enthalpy of mixing
• D. low entropy of mixing

Hint:

When considering immiscibility in polymer blends, the key thermodynamic factors are high enthalpy and low entropy of mixing.

Answer 1

The Correct Option is D

In binary polymer blends, immiscibility arises due to the thermodynamic properties of the system, particularly the enthalpy and entropy of mixing.

Step 1: Thermodynamic viewpoint on immiscibility.
When two substances are mixed, the free energy of mixing depends on both the enthalpy and entropy. If the enthalpy of mixing is very high or the entropy of mixing is very low, the free energy of mixing will be positive, leading to immiscibility.

Step 2: Analyzing the options.
- (A) low enthalpy of mixing: A low enthalpy of mixing would favor miscibility, not immiscibility. Hence, this is not the correct option.
- (B) high entropy of mixing: High entropy would also favor mixing, and would not explain immiscibility.
- (C) high enthalpy of mixing: A high enthalpy of mixing could make the free energy of mixing positive, but it does not explain the key thermodynamic factor in this case.
- (D) low entropy of mixing: A low entropy of mixing means that the system does not have enough disorder to drive the mixing, leading to immiscibility. This is the correct thermodynamic explanation for the immiscibility of polypropylene and polyamide 6.

Step 3: Conclusion.
The correct reason for the immiscibility of the polymer blends is low entropy of mixing, which results in a positive free energy of mixing and hence immiscibility.

Final Answer: (D) low entropy of mixing