Effects of precursor structure and imidization process on thermal expansion coefficient of polymide (BPDA/PDA)

Effects of the drying condition on thermo-mechanical properties and morphology of PI(BPDA/PDA) were investigated. Polyamic acid and polyamic acid esters were used as precursors of the polyimide. Thermal expansion coefficients (TECs) of the polyimide films are strongly affected by precursor structures. The esters give larger TECs than the polyamide acid does. TEC of polyimide film from polyamide acid depends on imidization conditions. The lowest TEC is obtained when the film is dried at 100°C and the value increases with the drying temperature. The TECs of the polyimide films formed from polyamide acid esters do not depend on the drying temperature. In summary, interactions between the precursors and solvent (NMP) lead to large differences in higher order structures of the polyimides, which in turn affects the TECs.