Carbon black (CB)-filled polyimide (PI) composites were prepared using self-degradated low molecular poly(amic acid) (PAA) as impurity-free dispersant.CB and PAA/N-methyl-2-pyrrolidone (NMP) solution were milled in ball miller.The impurity-free dispersant was prepared in the process of in situ degradation of PAA by high-energy milling process

which was active to carbon black (CB) surface.The effect of PAA modification on the CB particles was researched by Raman

IR and UV-Vis.TEM observation showed that the PAA modified CB particles dispersed uniformly in the mixtures with an average CB size of about 200 nm.The toughness

tensile strength and the reproducibility of resistivity for resulted CB/PI composite films were greatly improved.The elongation of resulted CB/PI films was raised at least 50%

and sample-to-sample variation of elongation was decreased from 17% to 11%.The tensile strength variation range was reduced from 12 MPa to 5 MPa.Resistivity variation range was decreased from two orders down to an order.The molecular weight of PAA added in milling progress played an important role on the dispersion of CB.The dispersion uniformity of CB in PI matrix was greatly improved as the increase of PAA molecular weight.