Facile fabrication of high-performance polyimide nanocomposites with in situ formed “impurity-free” dispersants

Abstract

Polyimide/carbon black (PI/CB) nanocomposite films were fabricated via the direct ball-milling method with poly(amic acid) (PAA), the precursor of PI, as an in situ formed impurity-free dispersant. FTIR and Raman spectral results reveal that, besides physical adsorption, chemical grafting of PAA chains onto the CB surface occurs during the ball-milling process. Comparative studies show that introduction of various commercial dispersants improves the dispersion of CB. However, the mixtures exhibit poor reproducibility, unstable electrical properties, and decreased tensile strength; these issues may be attributed to interfacial pollution brought about by differences in the chemical structures of the dispersant and the matrix. The impurity-free dispersant is effective not only in ensuring the uniform dispersion of CB particles but also in enhancing filler-matrix interfacial adhesion. High-molecular weight PAA chains are effective reagents for impurity-free modification and can therefore be used to improve the electrical and mechanical properties of the resultant composite.