POLYIMIDES
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Polyimides are strong, heat and chemically resistant polymers formed from acid dianhydrides and diamines. They have applications as coatings, insulators, and mechanical parts due to their strength and durability. Polyimides are synthesized through a two-step polyaddition and dehydration reaction of acid anhydrides and diamines. They can replace metals and glass in applications due to their high heat resistance, strength, and transparency to microwaves.
POLYIMIDES
- 2. INTRODUCTIONWhat are polyimides? what is the basic structural unit?Polyimides are polymers formed by the combination of acid dianhydrides and diamines.
- 3. TYPES OF POLY IMIDES : Linear polyimides
- 4. Aromatic hetero cyclic polyimides3
- 5. PHYSICAL AND THERMAL PROPERTIES:4
- 6. Other properties:Characteristic colour – orange/yellow
- 7. Very low creep
- 8. Inherent resistance to flame combustion
- 9. Un effected by commonly used solvents and oils
- 10. Un effected by hydro carbons, esters, alcohols and freons Resistant to weak acids
- 11. Not usable in alkaline or highly acidic environment.5
- 12. Significance of polyimides: Polyimides have high tensile strength.
- 13. They are highly heat resistant and chemical resistant.
- 14. They can often replace glass and metals such as steel.
- 15. They are transparent to microwave radiation.WHY POLYIMIDES ARE SO STRONG???CHARGE TRANSFER COMPLEX7
- 16. 8WHY POLYIMIDES ARE SO STRONG???
- 17. SYNTHESIS:By Step Growth Polymerization in two steps:1.Poly addition
- 19. They are prepared by the reaction of Acid Anhydrides and DiaminesIntially, soluble and fusible high molecular weight polyamic Acid is formed in polar aprotic solvent.
- 20. Later, Polyamic acid is processed into final insoluble and infusible polymer product. 9
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- 22. APPLICATIONS: Polyimides are used as struts and chasis in carsPolyimides are used as the outerlayer of thermal insulation covering of external surfaces of aircraftsThey are also used in vane brushes,bearings and washers for aircrafts
- 23. They are also used as polyimide heaters.
- 24. Polyimides are used in the cooking cavity of microwave oven.Polyimides are also used in food packaging.
- 25. Polyimides are used as mechanical stress buffers
- 26. As an insulating layer in the manufacture of IC chipsAs flexible cables in electronics industry
- 27. As a coating on tubes used in surgeries
- 28. As a photoresist in IC chip fabrication.BEARINGS MADE OF POLY IMIDEA POLYIMIDE RESINA POLYIMIDE TAPE16
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- 30. DEGRADATION OF POLYIMIDES:Photo Degradation: It is molecular degradation caused by ultraviolet radiation. Here bond between carbonyl carbon(C=O) and alkyl group breaks.Oxidative Degradation: It leads to hardening, discolouration and surface changes. In this R-C=O will be converted into R=C.|18
- 31. Structural and Environmental factors lead to thermal degradation of Polyimides This may be Thermal or thermo oxidative degradation
- 32. Cross linked bonds will break during thermal degradation
- 33. They will become insoluble in nature after thermal degradationThey retain their weight at elevated temperatures
- 34. Incase of aromatic polyimides, delocalization energy of Pi-electrons is released.THERMAL DEGRADATION OF POLYIMDES:19
- 35. BIBLIOGRAPHY:www.wikipedia.org Polymer Science and Technology by Joel R.Friedwww.google.com4. Text Book Of Polymer Science by Fred W. Billmeyer20
- 36. THANK YOU21