Question

Thermoplastic Polyurethane and Polyamide 6 both contain amide linkages, but when compared to Polyurethane, Polyamide 6 shows higher melting point due to ..............

• A. Higher molecular rigidity
• B. Higher degree of branching
• C. Lower molecular rigidity
• D. Lower degree of crosslinking

Hint:

Polyamide 6 exhibits higher molecular rigidity due to its crystalline structure, which allows for stronger intermolecular forces and a higher melting point compared to more flexible polymers like polyurethane.

Answer 1

The Correct Option is A

Polyurethane and Polyamide 6 are both thermoplastics that contain amide linkages, but they exhibit different physical properties due to the difference in their molecular structures.
- Molecular rigidity refers to the ability of polymer chains to resist deformation. Polyamide 6 (also known as nylon 6) has a highly regular, crystalline structure with strong intermolecular forces, contributing to its higher molecular rigidity compared to polyurethane. This increased rigidity results in a higher melting point for Polyamide 6.
- Degree of branching in a polymer affects its packing efficiency and mobility of chains. Polyurethane typically has a branched structure, which reduces the intermolecular forces between chains and thus lowers its rigidity. Polyamide 6, on the other hand, has fewer branches and more linearity, contributing to stronger intermolecular forces and a higher melting point.
- Crosslinking refers to the formation of bonds between polymer chains, leading to a networked structure. While crosslinking can increase rigidity, it is not the primary reason for the higher melting point of Polyamide 6 compared to Polyurethane.
Hence, the higher melting point of Polyamide 6 is primarily due to its higher molecular rigidity, making the correct answer (A) Higher molecular rigidity.