Polyimide/kaolinite composite films: Synthesis and characterization of mechanical, thermal and waterproof properties

Abstract Polyimide (PI)/kaolinite composites were successfully synthesized via in situ polymerization using kaolinite–potassium acetate intercalation compound (KKAc) as the intermediate. XRD patterns, FTIR spectrum and SEM images revealed that polyimide have partially intercalated into the layers of kaolinite by replacing KAc molecules. The mechanical, thermal and optical properties of the composite films were characterized by universal tester, TGA, and UV–vis spectrometer. It was found that the introduction of modified kaolinite led to significant increase in tensile strength and elongation at break of PI matrix when KKAc content was no more than 5 wt%. Electron microscopy characterization indicated that some plate-like and clusters-like structure appeared in perpendicular to the fracture surface of composite films after tensile tests other than in pure PI film, which meant stronger fracture resistance existing in the composite films. The introduction of modified kaolinite also resulted in improved thermal stability, slight decrease in transmittance and marked decrease in water uptake ratio at low clay content (≤5 wt%). Therefore, the polyimide/kaolinite composites have potential application in microelectronic devices.