Which of the following statements are incorrect about phenol formaldehyde resin ?

Options

A. Novolac or resol is a linear polymer and is used in the manufacture of adhesive
B. Bakelite is a cross linked polymer and is used in making switches and plugs
C. Novolac is prepared when (P/F) (phenol/formaldehyde) ratio if greater than 1, whereas bakelite is prepared when (P/F) ratio is less than 1
D. Novolac is prepared when `P//F lt 1` , and bakelite is prepared when `P//F gt 1`

Answer

To determine which statements about phenol formaldehyde resin are incorrect, we will analyze each provided statement step by step.

### Step-by-Step Solution:

1. **Understanding Novolac and Bakelite**:
- Novolac is a linear polymer made from phenol and formaldehyde.
- Bakelite is a cross-linked polymer also made from phenol and formaldehyde.

2. **Analyzing the First Statement**:
- The first statement claims that "Novolac is a linear polymer and is used in the manufacture of adhesives."
- This statement is correct because Novolac is indeed a linear polymer used for adhesives.

3. **Analyzing the Second Statement**:
- The second statement claims that "Bakelite is a cross-linked polymer and is used in making switches."
- This statement is also correct. Bakelite is a cross-linked polymer and is widely used in electrical switches and other applications.

4. **Analyzing the Third Statement**:
- The third statement claims that "Novolac is prepared when the phenol to formaldehyde (P:F) ratio is greater than 1, whereas Bakelite is prepared when the P:F ratio is less than 1."
- This statement is correct. Novolac is produced with a P:F ratio greater than 1, while Bakelite is produced with a P:F ratio less than 1.

5. **Analyzing the Fourth Statement**:
- The fourth statement claims that "Novolac is prepared when the P:F ratio is less than 1."
- This statement is incorrect because Novolac is actually prepared when the P:F ratio is greater than 1.

### Conclusion:
The incorrect statement about phenol formaldehyde resin is the fourth statement: "Novolac is prepared when P:F is less than 1."

### Final Answer:
The incorrect statement is: **Novolac is prepared when P:F is less than 1.**

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