Which of the following are characteristics of thermosetting polymers ?
I. Heavily branched cross linked polymers.
II. Linear, slightly branched long chain molecules.
III. Become infusible on moulding so cannot be reused.
IV. Have strongest molecular forces.
Choose the correct option.

Options

A. I and II
B. I,III and IV
C. Only II
D. Only III and IV

Answer

To determine the characteristics of thermosetting polymers, we will analyze each statement provided in the question:

**Step 1: Analyze Statement I**
- Statement I: "Heavily branched cross-linked polymers."
- Thermosetting polymers are indeed heavily branched and cross-linked. This structure contributes to their rigidity and strength. Therefore, this statement is **correct**.

**Step 2: Analyze Statement II**
- Statement II: "Linear, slightly branched long chain molecules."
- This statement describes thermoplastics rather than thermosetting polymers. Thermosetting polymers do not have a linear structure; they are cross-linked. Therefore, this statement is **incorrect**.

**Step 3: Analyze Statement III**
- Statement III: "Become infusible on moulding so cannot be reused."
- Thermosetting polymers undergo a curing process that makes them infusible. Once set, they cannot be melted and reshaped. Therefore, this statement is **correct**.

**Step 4: Analyze Statement IV**
- Statement IV: "Have strongest molecular forces."
- Thermosetting polymers exhibit strong intermolecular forces due to their cross-linked structure, making them more rigid and durable compared to thermoplastics. Therefore, this statement is **correct**.

**Conclusion:**
Based on the analysis:
- Correct statements are I, III, and IV.
- The incorrect statement is II.

Thus, the correct option is the one that includes statements I, III, and IV.

### Final Answer:
The correct characteristics of thermosetting polymers are:
- I. Heavily branched cross-linked polymers (Correct)
- II. Linear, slightly branched long chain molecules (Incorrect)
- III. Become infusible on moulding so cannot be reused (Correct)
- IV. Have strongest molecular forces (Correct)

### Correct Option:
The correct option includes statements I, III, and IV.

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