Polyimides
Formed with two step condensation. Fig 2-5
- First step: An aromatic dianhydride is reacted with an aromatic diamine to form polyamic (polamide) acid.
- Second step: Curing of the polyamic acid.
- Formation of imide group by closing of 5-member ring
- Condensation step of solvent molecules: water, alcohol, solvents
- Chain extension
- Cross-linking
- High viscosities of polyamid acids require use of prepregs.
- Impregnating the fiber mat with monomer solutions of diamines and diester acids.
- Long times and gradual increase in temperature are needed.
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