Question:
Which among the following is not a polyester ?
Which among the following is not a polyester ?
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Polyesters are "Alcohol + Acid". Polyamides are "Amine + Acid". Phenol-Formaldehyde resins (like Novolac and Bakelite) use formaldehyde as the linking agent, creating ether or methylene bridges.
Updated On: Feb 16, 2026
- Glyptal
- Novolac
- Dacron
- PHBV
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Concept:
Polymers are classified by the nature of the repeating functional group (linkage) in their backbone. Polyesters contain ester (\(-\text{COO}-\)) linkages formed by the condensation of polyhydric alcohols and polycarboxylic acids.
Step 2: Detailed Explanation:
1. Glyptal: Formed by the condensation polymerization of ethylene glycol and phthalic acid. It contains ester linkages. Hence, it is a polyester.
2. Dacron (Terylene): Formed by the condensation of ethylene glycol and terephthalic acid. It is a well-known polyester fiber.
3. PHBV: Poly(\(\beta\)-hydroxybutyrate-co-\(\beta\)-hydroxyvalerate) is a copolymer of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid. It contains ester linkages and is a biodegradable polyester.
4. Novolac: It is a linear polymer formed by the condensation of phenol and formaldehyde in an acidic medium. The monomeric units are linked by methylene (\(-\text{CH}_2-\)) bridges, not ester bonds. It is a precursor to Bakelite and belongs to the class of phenol-formaldehyde resins.
Step 3: Final Answer:
Novolac is not a polyester.
Polymers are classified by the nature of the repeating functional group (linkage) in their backbone. Polyesters contain ester (\(-\text{COO}-\)) linkages formed by the condensation of polyhydric alcohols and polycarboxylic acids.
Step 2: Detailed Explanation:
1. Glyptal: Formed by the condensation polymerization of ethylene glycol and phthalic acid. It contains ester linkages. Hence, it is a polyester.
2. Dacron (Terylene): Formed by the condensation of ethylene glycol and terephthalic acid. It is a well-known polyester fiber.
3. PHBV: Poly(\(\beta\)-hydroxybutyrate-co-\(\beta\)-hydroxyvalerate) is a copolymer of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid. It contains ester linkages and is a biodegradable polyester.
4. Novolac: It is a linear polymer formed by the condensation of phenol and formaldehyde in an acidic medium. The monomeric units are linked by methylene (\(-\text{CH}_2-\)) bridges, not ester bonds. It is a precursor to Bakelite and belongs to the class of phenol-formaldehyde resins.
Step 3: Final Answer:
Novolac is not a polyester.
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