Curing PAI by post-heating

The formation of the insoluble part in NMP was observed and the amount of insoluble part formed by heating of PAI-1 (obtained in MEK/water mixed solvent) was larger than that by heating of PAI-2 (obtained in DMAc). 

The increase of imide and amide bond content by post-heating at 260°C is considered as follows the imidation of amic acid structure may be proceeded by both intermolecular and intramolecular imidation. The latter produces cyclic imide bond, but the former produces acyclic imide bondto give crosslinking material as shown in Eq. [13.4.3]. 

Since PAIs obtained by heating of PAAAs at 180°C are completely soluble in NMP, the intramolecular imidation preferentially proceeds at 180°C, but intermolecular imidation scarcely proceeds. 

Therefore, PAI obtained from the heating of PAAA obtained in MEK/water mixed solvent, which has many carboxyl groups, produces more insoluble part by post-heating. 

4 CONCLUSIONS The effects of polymerization solvent on the curing of PAIs were investigated and the following results were obtained  

---