Synthesis and characterization of polyurethane rigid foams from soybean oil-based polyol and glycerol

Abstract

Mixtures of biomass-derived polyols were used to synthesize rigid polyurethane (PU) foams. A commercial polymerized methylene diphenyl diisocyanate (pMDI) was used as crosslinker, and distilled water served as foaming agent. The morphology and mechanical properties of foams with different glycerol and water contents were compared in order to evaluate the most suitable formulations. The rigid foams with higher water contents had larger and more anisotropic cells, explaining their lower density. Compressive moduli ranged from about 2.5 MPa to above 20 MPa and collapse stresses from 55 kPa to more than 1 MPa for densities between 54 and 143 kg/m3. Densification strain did not depend on the density or on the composition of the polymeric matrix. Moreover, results shown herein demonstrate that an increase in the glycerol content leads to an increase in the required pMDI for the synthesis of the PU, but with a negligible change in the mechanical properties of the prepared foams.