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

Options

A. Urea formaldehyde resin
B. PVC
C. Bakelite
D. Melamine formaldehyde resin

Explanation

To determine which of the given options can be remelted again and again without producing any change, we need to understand the properties of the materials listed.

### Step-by-Step Solution:

1. **Identify the Types of Polymers**:
- **Thermoplastics**: These are polymers that can be melted and remolded multiple times without undergoing any significant chemical change. They soften upon heating and harden upon cooling.
- **Thermosetting Polymers**: These polymers undergo a chemical change when heated and set into a rigid structure. Once they are set, they cannot be remelted or reshaped.

2. **Analyze Each Option**:
- **Option A: Urea Formaldehyde Resin**: This is a thermosetting polymer. Once it is set, it cannot be remelted.
- **Option B: PVC (Polyvinyl Chloride)**: This is a thermoplastic polymer. It can be remelted and reshaped multiple times without any change.
- **Option C: Bakelite**: This is also a thermosetting polymer. It cannot be remelted once it has set.
- **Option D: Melamine Formaldehyde Resin**: This is another thermosetting polymer. It cannot be remelted after it has set.

3. **Conclusion**:
- The only option that can be remelted again and again without producing any change is **Option B: PVC (Polyvinyl Chloride)**.

### Final Answer:
**Option B: PVC (Polyvinyl Chloride)** can be remelted again and again without producing any change.