Question
What are elastomers? Distinguish between thermoplastic polymers and thermosetting polymers.
✓
Answer
Polymers having the property of elasticity in which a substance gets stretched by external force and restores its original shape on the release of that force are called elastomers.
| Thermoplastic Polymer | Thermosetting Polymer |
| 1. These are formed by addition polymerisation . | These are formed by condensation polymerisation . |
| 2. They have low molecular weight . | They have high molecular weight. |
| 3.They are usually soft ,weak and less brittle . | hey are usually hard ,strong and more brittle |
| 4. They are long chain linear polymer with negligible cross links | They have three-dimensional network structure with number of crosslinks . |
| 5. They are usually soluble in some organic solvents . | Due to strong bonds and crosslinks ,they are insoluble in almost all organic solvents . |
| 6. They get softened on reheating readily because secondary forces between the individual chain can break easily by heat or pressure . | They donot soften on reheating because the crosslinks and bonds retain their strength on heating . |
| 7.Example : Polyethylene ,Polystyrene ,PVC ,PVA . | Example : Phenolformaldehyde,ureaformaldehyde , Nylon 6,6 . |
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