Which of the following polymers do not involve crosslinkages?

Options

A. Melmac
B. Bakelite
C. Polythene
D. Vulcanised rubber

Explanation

To determine which of the given polymers do not involve crosslinkages, let's analyze each option step by step.

### Step 1: Understand Crosslinkages
Crosslinkages refer to the connections between different polymer chains. These connections can be covalent bonds or other types of interactions that link the chains together, affecting the properties of the polymer.

### Step 2: Analyze Each Polymer
1. **Melamac (Melamine Resin)**:
- Melamine resin is formed from the polymerization of melamine and formaldehyde.
- The structure involves crosslinkages due to the reaction of melamine's amine groups with formaldehyde, creating a network structure.
- **Conclusion**: Melamac has crosslinkages.

2. **Bakelite**:
- Bakelite is a condensation polymer made from phenol and formaldehyde.
- Similar to melamine, Bakelite forms a three-dimensional network due to crosslinking between the polymer chains.
- **Conclusion**: Bakelite has crosslinkages.

3. **Polyethylene**:
- Polyethylene is formed from the polymerization of ethylene monomers.
- The structure of polyethylene is linear, and it does not have crosslinkages between the chains.
- **Conclusion**: Polyethylene does not have crosslinkages.

4. **Vulcanized Rubber**:
- Vulcanized rubber is made from natural rubber (polyisoprene) that has been treated with sulfur.
- This process introduces disulfide linkages, which act as crosslinks between the rubber chains.
- **Conclusion**: Vulcanized rubber has crosslinkages.

### Step 3: Identify the Polymer Without Crosslinkages
Based on the analysis:
- **Polyethylene** is the only polymer among the options that does not involve crosslinkages.

### Final Answer
The polymer that does not involve crosslinkages is **Polyethylene**.

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