Study on synthesis of polyamic acid and polyimide by microwave irradiation

The copolycondesation type polyamic acid(PAA) was synthesized by using pyromellitic dianhydride(PMDA) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride(BTDA) as the dianhydride monomers,4,4'-diamino diphenylmethane(MDA) and 4,4'-oxydianiline(ODA) as the diamine monomers under microwave irradiation in dimethylformamide(DMF).Then PAA came into being polyimide(PI) by an imidization.The structure and performance of polymer were characterized by viscosity,FT-IR,TG analyses,XRD and so on.The results showed that under microwave irradiation,the intrinsic viscosity and the yield of PAA were raised,and the reaction time was shortened.The FT-IR spectra of polymer were shown that,there were PI's characteristic peaks around 1 775 cm-1 and 1 724 cm-1.Thermogravimetric curve indicated that,PI's 5% thermal decomposition temperature under N2 was 477 ℃and its 10% thermal decomposition temperature under N2 was 553 ℃.