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.

1. POLYIMIDES-K.SAI MALLESWAR

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

18. 2.Subsequent Dehydration

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

21. 10