Oil epoxies can be used as plasticizers in the processing of hard polymers. For this purpose dehydrated castor oil epoxv (DCOE), a product from sustainable resource, has bean chosen for blending with poly(methyl methacrylate) (PMMA) to investigate the compatibility of this blend pair. Blends of DCOE/PMMA were prepared in the weight ratios 80/20, 60/40, 40/60, and 20/80 through solution method by mixing in dimethylsulphoxide. Freestanding films of the blend were cast and the miscibility of the two components was investigated by viscosity and ultrasonic measurements, which provided valuable information on the degree of compatibility of the pairs of blends in Solution. The compatibility was also examined by differential scanning calorimetry and scanning electron microscopy. All the studies revealed that DCOE was immiscible with PMMA. However, the appearance and texture of the films were not found to show any visible change over several months, which indicates stability of this blend system. 0 2006 Wiley Periodicals, Inc.