Polyimides
Addition Polyimides
- Many polyimids are cross linked with an addition reaction
- Two general cross-linking reactions are widely used
- End group reactions
- Bismaleimide reactions
- Reactive End Group Resin Fig 2-6
- First phase (imidization): results in the formation of the oligomeric (small polymer) imide
- Second phase (consolation): is when the oligomer melts and flows to fill voids that were created from volatiles depart.
- Third phase (crosslinking): oligomer builds MW & crosslinks
- Shorter polymer chains gave lower viscosity and better wet-out
- Wet-out is defined as uniform coating and soaking of resin in fiber.
- Commercial end group resin (PMR) is PMR 11, PMR 15 and PMR 20
- PMR-11 has more end groups and higher cross-linking density and higher stiffness
- PMR-20 gave better thermal stability.
- PMR-15 has the best physical properties balanced.
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