Which of the following polymers are thermoplastic?

Options

A. Teflon
B. Natural rubber
C. Neoprene
D. Polystyrene

Explanation

To determine which of the given polymers are thermoplastic, we need to understand the characteristics of thermoplastic polymers and analyze each option accordingly.

### Step-by-Step Solution:

1. **Understand Thermoplastic Polymers**:
- Thermoplastic polymers are characterized by their linear or slightly branched chain structures.
- They are hard at room temperature but become soft or viscous when heated.
- Upon cooling, they regain their rigidity, and this process can be repeated multiple times without altering their chemical composition.

2. **Analyze Each Option**:
- **Teflon**:
- Teflon is known to be a thermoplastic polymer. It is hard at room temperature and becomes soft when heated, allowing it to be molded and reshaped. Upon cooling, it regains its rigidity.
- **Conclusion**: Teflon is a thermoplastic polymer.

- **Natural Rubber**:
- Natural rubber is classified as an elastomer. It has weak Van der Waals forces between its chains, allowing it to stretch and return to its original shape.
- **Conclusion**: Natural rubber is not a thermoplastic polymer.

- **Neoprene**:
- Neoprene is also an elastomer, similar to natural rubber. It can be stretched and will return to its original form when the force is removed.
- **Conclusion**: Neoprene is not a thermoplastic polymer.

- **Polystyrene**:
- Polystyrene is a thermoplastic polymer. It has a linear structure and is hard at room temperature. It can be softened by heating and regains its rigidity upon cooling.
- **Conclusion**: Polystyrene is a thermoplastic polymer.

3. **Final Answer**:
- From the analysis, the thermoplastic polymers among the given options are **Teflon and Polystyrene**.