Which of the following can be remelted time and again without producting any change?

Options

A. Thermosetting polymers
B. Thermoplastic polymers
C. Bakelite
D. Melamine

Answer

To solve the question "Which of the following can be remelted time and again without producing any change?", we will analyze the given options based on the properties of different types of polymers.

### Step-by-Step Solution:

1. **Understand the Types of Polymers**:
- **Thermosetting Polymers**: These polymers, once set or hardened, cannot be remelted or reshaped. They undergo a chemical change during the curing process, which makes them rigid and inflexible.
- **Thermoplastic Polymers**: These polymers can be melted and remolded multiple times without undergoing any chemical change. They soften upon heating and harden upon cooling, allowing for reshaping.

2. **Evaluate the Options**:
- **Option 1: Thermosetting Polymers**: As mentioned, these cannot be remelted once they are set. Therefore, they do not fit the criteria of being remeltable.
- **Option 2: Thermoplastic Polymers**: These can be remelted and reshaped repeatedly without any change in their chemical structure. This option fits the criteria perfectly.
- **Option 3: Bakelite**: Bakelite is a type of thermosetting polymer. Once it is set, it cannot be remelted or reshaped. Hence, this option is incorrect.
- **Option 4: Melamine**: Melamine is also a thermosetting polymer, specifically a melamine-formaldehyde resin. Like Bakelite, it cannot be remelted once it is cured. Therefore, this option is also incorrect.

3. **Conclusion**:
Based on the analysis, the only option that can be remelted time and again without producing any change is **thermoplastic polymers**.

### Final Answer:
**Thermoplastic Polymers** can be remelted time and again without producing any change.

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