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Questions and Answers
Polyacrylonitrile is a substitute for silk in making commercial fibers.
False
Buna S is a type of natural rubber.
False
Neoprene is a type of synthetic rubber.
True
Vulcanization of rubber involves heating it with oxygen.
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Poly Vinyl Chloride is a type of synthetic fiber.
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Addition polymerization involves the condensation of monomers with double and triple bonds.
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Condensation polymerization involves the addition of monomers with double and triple bonds.
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Nylon 6,6 is obtained by heating caprolactum with water.
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Terelene is a type of polyamide.
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Bakelite is a type of polyamide.
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Study Notes
Polymerization
- Polymers are macromolecules formed by joining of repeating structural units on a large scale.
- The repeating structural units are called Monomers.
Monomers and Polymers
- Monomers are small molecules that combine with each other to form polymer molecules.
- Macromolecules refer to large molecules built from smaller subunits.
- When all the subunits are of the same type, the macromolecules are called polymers, and the subunits are monomers.
- Examples of polymers: DNA, proteins, carbohydrates.
- Example of macromolecule: triglycerides (fat).
Classification of Polymers
Based on Source
- Natural polymers: occur in nature (e.g. protein, nucleic acid, cellulose, starch).
- Semi-synthetic polymers: derived from natural sources, but undergo chemical treatment (e.g. cellulose nitrate, cellulose acetate).
- Synthetic polymers: man-made (e.g. plastics, Nylon, Buna-s, PVC, polyethylene).
Based on Structure
- Linear polymers: long chains (e.g. high-density polythene, polyvinyl chloride).
- Branched chain polymers: chain with branches (e.g. low-density polythene).
- Cross-linked or network polymers: string covalent bond between chains (e.g. Bakelite, Melamine).
Based on Type of Monomer
- Homo polymer: made from only one monomer (e.g. A-A-A-A-A-A-A-A).
- Co-polymer: made from two or more different monomers.
- Types of co-polymers:
- Random copolymer: -A-B-B-A-B-A-A-B-
- Alternating copolymer: -A-B-A-B-A-B-A-B-
- Block copolymer: -A-A-A-A-B-B-B-B-
- Graft copolymer:
- Types of co-polymers:
Based on Molecular Forces
- Elastomers: weakest intermolecular forces (e.g. rubber, buna-S).
- Fibers: strongest intermolecular forces (e.g. Nylon, Polyesters, Terylene).
- Thermoplastic: can be remolded by heating and cooling (e.g. Polythene, PVC).
- Thermosetting Plastic: cannot be reused (e.g. Bakelite, urea formaldehyde).
Based on Mode of Polymerization
- Addition polymerization: monomer contains one double bond.
- Condensation polymerization: monomer contains bi-functional group.
Addition Polymerization
- Examples of addition polymers:
- Polythene (two types)
- Teflon (Polytetrafluoroethene)
- Polyacrylonitrile
- Buna S
- Natural Rubber (cis-1,4-poly isoprene)
- Synthetic Rubber (Neoprene, Buna-N)
- Poly Vinyl Chloride (PVC)
- Poly styrene
Vulcanization of Rubber
- Heating with sulphur and an additive to improve physical properties of natural rubber.
Mechanism of Addition Polymerization
- Step 1: Chain initiating step
- Step 2: Chain propagation
- Step 3: Chain termination
Condensation Polymerization
- Involves repetitive condensation between two bi-functional monomers, with loss of simple molecules (e.g. water, alcohol).
- Examples:
- Polyamides (Nylon 6,6, Nylon 6)
- Polyesters (Terelene, Glyptal)
- Phenol Formaldehyde Polymer (Bakelite)
- Melamine Formaldehyde Polymer
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Description
Learn about polymers, macromolecules formed by joining repeating structural units, and understand the process of polymerization and the differences between polymers and macromolecules.
