How many among the following are biodegradable polymers?
(i) Polyhydroxybutyrate (PHB)
(ii) PHBV
(iii) SBR
(iv) Polyglycolic acid
(v) Bakelite
(vi) Thiokol
(vii) Nylon-2-Nylon-6
(vii) PMMA
(ix) Nylon-6, 6.

Answer

To determine how many of the listed polymers are biodegradable, we will analyze each polymer one by one.

### Step 1: Identify each polymer and its biodegradability

1. **Polyhydroxybutyrate (PHB)**:
- PHB is a biodegradable polymer produced by bacterial fermentation of sugars or lipids.
- **Biodegradable? Yes.**

2. **PHBV (Polyhydroxybutyrate-co-valerate)**:
- PHBV is a copolymer of PHB and is also biodegradable.
- **Biodegradable? Yes.**

3. **SBR (Styrene-Butadiene Rubber)**:
- SBR is a synthetic rubber that is not biodegradable and is used in tires and other applications.
- **Biodegradable? No.**

4. **Polyglycolic acid (PGA)**:
- PGA is a biodegradable polymer often used in medical applications, such as sutures.
- **Biodegradable? Yes.**

5. **Bakelite**:
- Bakelite is a thermosetting plastic that is not biodegradable.
- **Biodegradable? No.**

6. **Thiokol**:
- Thiokol is a type of rubber that is not biodegradable.
- **Biodegradable? No.**

7. **Nylon-2-Nylon-6**:
- This is a type of nylon that is considered biodegradable under certain conditions.
- **Biodegradable? Yes.**

8. **PMMA (Polymethyl methacrylate)**:
- PMMA is a synthetic polymer that is not biodegradable.
- **Biodegradable? No.**

9. **Nylon-6,6**:
- Nylon-6,6 is a synthetic polymer that is not biodegradable.
- **Biodegradable? No.**

### Step 2: Count the biodegradable polymers

From the analysis:
- Biodegradable polymers: PHB, PHBV, PGA, Nylon-2-Nylon-6.
- Total biodegradable polymers = 4.

### Final Answer
**There are 4 biodegradable polymers among the listed options.**

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