Abstract The dispersion ability of fluorene‐based epoxy resin (FBE), bisphenol A based epoxy resin (PBE), fluorene‐based polyester (FBP), and polycarbonate (PC) in carbon black (CB) was evaluated. CB/FBE composite had a lower L value (reflectance, blackness) than that of CB/PBE composite, for the same CB content. Aggregations of CB in CB/FBE composites were much smaller than those in CB/PBE composites. The strong interaction between fluorene with cardo structure and CB resulted in a fine dispersion of CB in FBE. FBP had much higher dispersion ability of CB than PC. CB (50 wt%) was dispersed into FBP compared with the 10 wt% of CB dispersed in PC by melt blending. The effect of CB on the mechanical properties of FBP was much higher than that on PC due to fine dispersion of CB in FBP. The effect of CB addition on the T g of FBP was also higher than that of CB on the T g of PC. Computational simulation indicates that most stable energy between fluorene with a cardo structure and graphite structure was smaller than the energy between bisphenol A and graphite. It was also shown that the minimum energy appeared when the fluorene structure was almost parallel to the graphite plane. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers