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PVC

Classification of polymers according to their thermal behaviours: 1) THERMOPLASTICS. Thermoplastic polymers can be softened when heated and hardened when cooled with little change in their properties, repeatedly.

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PVC

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  1. Classification of polymers according to their thermal behaviours: 1) THERMOPLASTICS • Thermoplastic polymers can be softened when heated and hardened when cooled with little change in their properties, repeatedly. • The softening/melting occurs as the polymer chain move more and more freely because of absence of cross link. PE PS PVC

  2. Classification of polymers according to their thermal behaviours: 2) THERMOSETS EPOXY BINDERS: Thermosets are generally prepared from low molecular mass semifluid substances. When heated they get highly cross linked to form rigid and insoluble products. The cross links hold the molecule in place so that heating does not allow them to move freely.

  3. Thermoplastics can be heated and shaped over and over again - Thermosetting plastics can only be heated and shaped once. ....

  4. FIBERS These polymers which have strong intermolecular forces between the chains. These forces are either hydrogen bonds or dipole-dipole interactions. Because of strong intermolecular forces, the chains are closely packed giving them high tensile strength and less elasticity. Therefore, these polymers have sharp melting points. Therefore, these are used for making fibres. Carpet Fiber

  5. FIBERS: Kevlar

  6. Elastomers: the polymers can be easily stretched by applying small stress and regains their original shape when the stress is removed. The most important example of elastomers is natural rubber. The molecular structure of elastomers can be imagined as a 'spaghetti and meatball' structure, with the meatballs signifying cross-links. Cross-linkages ensure that the elastomer will return to its original configuration when the stress is removed. The principal difference between thermoset elastomers and thermoplastic elastomers is the type of crosslinking bond in their structures.

  7. Thermoplastic elastomer: Spandex Spandex: DuPont sells under the trade name Lycra

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