Question

Choose the correct statement

• A. Thermoplastics are either amorphous or crystalline
• B. Thermoplastics are crystalline
• C. Thermosetting and thermoplastics polymers are essentially amorphous
• D. Thermosetting plastics are crystalline

Hint:

Thermoplastics soften when heated and harden when cooled, while thermosetting plastics undergo permanent chemical cross-linking and cannot be remelted.

Answer 1

The Correct Option is A

Thermoplastics and thermosetting plastics are two major classes of polymers, differing in structure and behavior upon heating. Step 1: Understanding Thermoplastics and Thermosetting Plastics - Thermoplastics: These polymers can be either amorphous or crystalline. Examples include polyethylene (crystalline) and polystyrene (amorphous). - Thermosetting Plastics: These are generally amorphous and cannot be remelted after curing (e.g., epoxy, Bakelite).

Step 2: Evaluating the Statements - Option (A) - Correct: Thermoplastics can be either crystalline (e.g., polyethylene, polypropylene) or amorphous (e.g., polycarbonate, PMMA).
- Option (B) - Incorrect: Not all thermoplastics are crystalline; some are amorphous.
- Option (C) - Incorrect: Thermoplastics can be crystalline, so this statement is false.
- Option (D) - Incorrect: Thermosetting plastics are typically amorphous, not crystalline.

Step 3: Conclusion Since thermoplastics can be either amorphous or crystalline, the correct answer is option (A).