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प्रश्न
Explain thermoplastic and thermosetting polymers.
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उत्तर
Thermoplastic polymers:
- Thermoplastic polymers have the property of plasticity, that is, these polymers can be easily shaped or moulded.
- They are capable of repeated softening on heating and hardening on cooling.
- These polymers possess moderately strong intermolecular forces that are intermediate between elastomers and fibres.
e.g. Polythene, polystyrene, polyvinyl, etc.
Thermosetting polymers:
- Thermosetting polymers are rigid polymers.
- During their formation, they have the property of being shaped on heating; but they get hardened while hot. Once hardened, they cannot be softened by heating and therefore cannot be remoulded.
- This characteristic is the result of extensive cross-linking by covalent bonds formed in the moulds during the hardening/setting process while hot.
e.g. Bakelite, urea-formaldehyde resin, etc.
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\[\begin{array}{cc}
\ce{-(CH2 - CH2 - CH - CH2 - CH2)_\text{n}}\\
|\phantom{..}\\\ce{\phantom{..}CH2}\\
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