Polymer/organoclay nanocomposite systems were prepared from biodegradable aliphatic polyester (BAP)-poly(epichlorohydrin) (PECH) blends via the solvent casting method. From X-ray diffraction analysis, it was confirmed that the increased interlayer distance of the clay was solely affected by the BAP, implying that the BAP has better affinity to clay than PECH in a competitive intercalation mechanism. To clarify the sole effect of clay on polymer blend nanocomposite systems, we fixed the clay content at 3 wt%. The mechanical properties and rheological characteristics in steady and oscillatory shear modes of BAP-PECH/clay nanocomposites were investigated and compared with those of BAP-PECH blends without clay. (c) 2005 Springer Science + Business Media, Inc.