Polymers are an important topic in ECET Chemistry. Many direct questions are asked about classification, examples, and applications. By mastering this chapter, you can secure easy marks.
📘 Concept Notes – Polymers
🌐 What is a Polymer?
- Polymer = Large molecule formed by repeated units (monomers).
- Polymerization = chemical process in which monomers link together.
⚙️ Classification of Polymers
1️⃣ Based on Source
- Natural polymers: Proteins, cellulose, rubber.
- Synthetic polymers: PVC, nylon, polythene.
- Semi-synthetic polymers: Rayon, cellulose acetate.
2️⃣ Based on Structure
- Linear polymers: Chains arranged in straight line (e.g., PVC, polythene).
- Branched polymers: Chains with side branches (e.g., low-density polythene).
- Cross-linked / Network polymers: Chains interconnected in 3D (e.g., bakelite, melamine).
3️⃣ Based on Mode of Polymerization
- Addition polymers: Formed by addition reaction of monomers with double bonds.
- Example:
(Polythene).
- Example:
- Condensation polymers: Formed by condensation reaction with elimination of small molecules (H₂O, HCl).
- Example: Nylon-6,6 from adipic acid + hexamethylene diamine.
4️⃣ Based on Molecular Forces
- Elastomers: Weak van der Waals forces, can be stretched (rubber).
- Fibres: Strong H-bonding, high tensile strength (nylon, polyester).
- Thermoplastics: Linear/branched polymers, soften on heating (PVC, polythene).
- Thermosetting plastics: Cross-linked polymers, hard and infusible (bakelite, urea-formaldehyde).
🔋 Important Formula
Degree of polymerization (DP):
📐 Example
- Molecular mass of polythene sample =
- Monomer =
🔟 10 Expected MCQs – ECET 2026
Q1. Which of the following is a natural polymer?
A) Nylon
B) Cellulose
C) PVC
D) Rayon
Q2. PVC is an example of:
A) Natural polymer
B) Semi-synthetic polymer
C) Synthetic polymer
D) Elastomer
Q3. Low-density polythene is a:
A) Linear polymer
B) Branched polymer
C) Network polymer
D) Fibre
Q4. Bakelite is an example of:
A) Linear polymer
B) Branched polymer
C) Thermosetting polymer
D) Thermoplastic polymer
Q5. Nylon-6,6 is prepared by condensation of:
A) Adipic acid + hexamethylene diamine
B) Ethylene glycol + terephthalic acid
C) Caprolactam
D) Styrene
Q6. Which of the following is an elastomer?
A) Rubber
B) PVC
C) Nylon
D) Bakelite
Q7. Degree of polymerization is defined as:
A) Number of bonds per chain
B) Number of repeating units per chain
C) Number of molecules per mole
D) None
Q8. Which type of bonding gives fibres high tensile strength?
A) Covalent
B) Metallic
C) Hydrogen bonding
D) Ionic
Q9. Polythene is obtained by addition polymerization of:
A) Ethylene
B) Styrene
C) Propylene
D) Acetylene
Q10. Rayon is classified as:
A) Natural polymer
B) Semi-synthetic polymer
C) Synthetic polymer
D) Thermoplastic
✅ Answer Key
| Q.No | Answer |
|---|---|
| Q1 | B |
| Q2 | C |
| Q3 | B |
| Q4 | C |
| Q5 | A |
| Q6 | A |
| Q7 | B |
| Q8 | C |
| Q9 | A |
| Q10 | B |
🧠 Explanations
- Q1 → B: Cellulose is natural polymer.
- Q2 → C: PVC is fully synthetic.
- Q3 → B: LDPE = branched polymer.
- Q4 → C: Bakelite is thermosetting.
- Q5 → A: Nylon-6,6 = adipic acid + hexamethylene diamine.
- Q6 → A: Rubber is an elastomer.
- Q7 → B: DP = number of repeating units.
- Q8 → C: Fibres (nylon, polyester) → strong due to H-bonding.
- Q9 → A: Polythene from ethylene.
- Q10 → B: Rayon = semi-synthetic.
🎯 Why Practice Matters
- Polymer classification is a repeated topic in ECET exams.
- Questions are straightforward and mostly theory + 1 formula (DP).
- Easy to secure marks if you memorize examples.
