Karanja Oil Polyol and Rigid Polyurethane Biofoams for Thermal Insulation

Abstract

Rigid polyurethane biofoams were prepared from karanja polyol which was derived by ring-opening reaction of epoxidized karanja oil. The polyol, which had a hydroxyl value of 186 mg KOH/g, was thoroughly characterized and the structure confirmed by spectral techniques. The foam formulations were developed to achieve shrinkage-free foams with water used as the blowing agent. The resulting foams were characterized for their mechanical properties like density, compression strength and flexural strength. The densities and mechanical properties, such as compression and flexural strength, varied with the amount of methylene diphenyl diisocyanate (MDI) for a fixed amount of polyol and other additives as a result of side reactions leading to allophanate and urea linkages. Scanning electron microscopy (SEM) results indicated that the cells are spherical and samples are isotropic. However, the cell size distribution varied with MDI content. The thermal conductivity was found to be in the 0.036–0.042 W/m.K range, which is well suited for insulation purposes.