Which of the following is used in the manufacture of thermosetting plastics ?

Options

A. Formaldehyde
B. Acetaldehyde
C. Acetone
D. Benzaldehyde

Answer

To determine which of the following is used in the manufacture of thermosetting plastics, we need to understand the properties and examples of thermosetting plastics.

### Step-by-Step Solution:

1. **Understanding Thermosetting Plastics**:
- Thermosetting plastics are polymers that harden permanently after being shaped. They cannot be remolded or reshaped upon heating.
- They are characterized by their rigidity and hardness, which is due to the presence of cross-linking between polymer chains.

2. **Properties of Thermosetting Plastics**:
- They maintain a permanent shape and structure.
- The cross-linking is typically achieved through covalent bonds, which create a three-dimensional network of polymer chains.

3. **Examples of Thermosetting Plastics**:
- The most notable example of thermosetting plastic is **Bakelite**.
- Bakelite is formed from the reaction of phenol and formaldehyde, resulting in a cross-linked polymer.

4. **Other Examples**:
- Another example is **Urea-formaldehyde resin**, which is commonly used in the production of plywood and other composite materials.

5. **Conclusion**:
- Based on the information gathered, the correct answer to the question is **Formaldehyde resin**, as it is a key component in the manufacture of thermosetting plastics like Bakelite and Urea-formaldehyde resin.

### Final Answer:
**Formaldehyde resin is used in the manufacture of thermosetting plastics.**

---