Rigid Polyurethane Foam Based on Modified Vegetable Oil

ABSTRACT: Soybean oil and castor oil were modified and used to prepare rigid polyurethane foam with similar properties to a commercial foam used for thermal insula-tion applications. Soybean oil was firstly modified accord-ing to a peracid method, using formic acid and hydrogen peroxide to yield a formiated soy polyol. Furthermore, transesterification was performed with a polyfunctional alcohol to increase OH-functionality. Castor oil, which has hydroxyl groups in the molecular structure, was only trans-esterified. The vegetable polyols were characterized by OH-number, Brookfield viscosity, differential scanning calorim-etry, and size exclusion chromatography. The foams were prepared at constant NCO/OH ratio (1.2: 1) by the hand mix method and poured into a closed steel box. They were characterized using scanning electron microscopy, ther-mogravimetric analysis, and dynamic mechanical analysis. The apparent density and the compression strength of foams were determined, respectively, by the mass/volume relation and through the table tensile tester. After modifica-tion, the polyols reached an OH-number between 393 and 477 mg KOH/g oil, showing a low viscosity and molecular weight, allowing the preparation of a rigid vegetable foam with an apparent density of 50 6 1 kg/m3 and compressio