Which of the following is/are not a fibre ?

Options

A. Bakellite
B. Polyethylene
C. Nylon-6
D. Natural rubber

Explanation

To determine which of the following options are not fibers, we need to analyze each option based on their characteristics and classifications in polymer chemistry.

### Step-by-Step Solution:

1. **Understanding Fibers**:
- Fibers are thread-forming solids that possess high tensile strength and high modulus. They are characterized by strong intermolecular forces such as hydrogen bonding, which leads to close packing of polymer chains and imparts a crystalline nature.

2. **Analyzing the Options**:
- **Option 1: Vagalite**
- Vagalite is a type of thermosetting polymer. Thermosetting polymers do not have the properties of fibers as they do not form flexible threads and are not suitable for applications requiring high tensile strength in a fiber form.
- **Option 2: Polyethylene**
- Polyethylene is a thermoplastic polymer. While it can be made into fibers (like in the case of polyethylene fibers), in its common form, it does not exhibit the necessary properties of a fiber. Thus, it is not classified as a fiber.
- **Option 3: Nylon 6**
- Nylon 6 is a polyamide and is widely recognized as a fiber. It possesses the necessary properties such as high tensile strength and is used in textiles, making it a fiber.
- **Option 4: Natural Rubber**
- Natural rubber is derived from cis-1,4-isoprene and is classified as an elastomer. While it can be spun into fibers, it is primarily known for its elasticity and flexibility rather than its fiber-forming capabilities.

3. **Conclusion**:
- Based on the analysis, the options that are not fibers are:
- Vagalite (Option 1)
- Polyethylene (Option 2)
- Natural Rubber (Option 4)
- The only option that is a fiber is Nylon 6 (Option 3).

### Final Answer:
The options that are not fibers are **Vagalite, Polyethylene, and Natural Rubber**.