Thesis (Ph.D.)--Chulalongkorn University, 2011

The preparation of bio-based polyols for rigid polyurethane (RPUR) foams is the main objective of this research. Three vegetable oils including hairy basil seed oil, sesame seed oil, and pumpkin seed oil have been used to synthesize bio-based polyols. The synthesis of vegetable oil-based polyols involved two steps, namely the hydroxylation and the alcoholysis reaction. The resulting polyols had the OH number in the range of 340–383 mg KOH/g. The water-blown RPUR foams were produced by the reaction of these bio-based polyols with polymeric methylene diphenyl diisocyanate (PMDI). The effects of isocyanate index, catalyst, blowing agent, and surfactant contents on the reaction time and their density were evaluated. The results showed that these parameters except the surfactant content significantly affected on the foaming time and foam density depending upon the synthesized polyol type. An increase in NCO index and blowing agent contents resulted in the longer reaction time, the foam density at higher NCO index was raised gradually that contrast to the effect of blowing agent content. As the catalyst contents increased, the reaction time was reduced with a decrease in density of foams. These vegetable oil-based RPUR foams exhibited relatively high compressive strength (237.7–303.1 kPa) with the density in the range of 40–45 kg/m3. Additionally, the cell foam morphology investigated by scanning electron microscope indicated that their cellular structure presented mostly polygonal closed-cells. These detailed experimental analyses supported that the water-blown RPUR foams prepared from these bio-based polyols possessed comparable the physical, mechanical, and thermal properties to those obtained from the commercial polyols.