Nylon-6 as compared to nylon-66 is

Answer: Option D

Nylon-6 and Nylon-66 are both types of polyamides but differ in their molecular structure and properties.

Nylon-6 is produced from a single monomer, caprolactam, whereas Nylon-66 is made from two monomers: adipic acid and hexamethylenediamine.

Hardness: Nylon-66 is harder than Nylon-6 due to its higher crystallinity and symmetrical structure. So, Option A is incorrect.

Abrasion Resistance: Nylon-66 has better abrasion resistance than Nylon-6 because of its denser molecular packing. Thus, Option B is also incorrect.

Melting Point: Nylon-66 has a higher melting point (around 255–265°C) than Nylon-6 (around 220–230°C) because of stronger hydrogen bonding. Hence, Option C is incorrect.

Conclusion: Since none of the statements are true when comparing Nylon-6 to Nylon-66, the correct answer is Option D: None of these.