Series of polyurethanes (PUs) based on PHB and castor oil CO were prepared using hexamethylene diisocyanate as a coupling agent. Nanocomposites of the prepared PUs were also prepared using cloisite 25A as nanofiller with different contents. FTIR an increment in the surface roughness with increasing both PHB and C25A. DSC showed that the samples exhibited two T_g values for both PHB and castor oil. The physical transition temperatures were found to depend on the contents of PHB, CO and C25A. The degradation behavior was studied using thermogravimetric analysis.