Impact of modification of carbon black on morphology and performance of polyimide/carbon black hybrid composites

The composite films based on polyimide (PI) and chloride modified carbon black (CB-COCl) were prepared by conversion of biphenyltetracarboxylic dianhydride and 4,4'-oxydianiline in the presence of CB-COCl, followed by thermal imidization. The presence of chemical bonds between PI and CB-COCl, proved by FTIR spectra of the composites, has a considerable effect on the properties of PI films. Scanning electron microscopy (SEM) pictures of the PI/CB-COCl membranes showed changed morphology compared to reference membranes without CB-COCl. The thermal stability and structure of the composites were studied by differential scanning calorimetry (DSC), thermogravimetric analyses (TGA) and X-ray diffraction (XRD), respectively. These hybrid films showed an increase in thermal decomposition temperature and a slightly enhanced glass transition temperature. On their mechanical properties, the modulus and ultimate strength of the hybrid films increased and elongation at break decreased with increased CB-COCl content. The surface free energy of polyimide films were determined by means of the contact angle measurements.