Synthesis And Characterization Of Bio-based Polyols From Epoxidized Soybean Oil and Their Use For The Synthesis Of Polyurethanes

Nowadays, the polyurethane (PU) industry is looking for renewable raw materials to replace two major feedstocks, polyols and isocyanates, which derive from petroleum sources, because of the uncertainty about the cost of petroleum in the future and the need to move toward more environmentally friendly feedstocks. PUs industry is making research efforts for replacing oil-based polyols with polyols from renewable resources, such as bio-polyols from vegetable oils. Until now, different synthetic strategies have been developed to obtain polyols, including the modification of epoxidized triglycerides by fatty acids. Herein, an epoxidized soybean oil (ESO) with a percentage of epoxy groups equal to 4.8% and 21% oleic, 60% linoleic and 7% linolenic chains was used. A wide screening was performed to identify the best fatty acids to obtain low molecular weight polyols with narrow polydispersity using solvent- and catalyst-free reactions (Step 1). Then a selected bio-based polyol has been tested in the preparation of different composite PUs and their properties have been evaluated as well (Step 2). Step 1-Synthesis of bio-based polyols: Glutaric acid (C5H8O4), caprilic acid (C8H16O2), thioglycolic acid (C2H4O2S), 3-phenylbutyric acid (C10H12O2), stearic acid (C18H36O2) and oleic acid (C18H34O2) were used. Different substituents (such as carboxy, aryl groups and heteroatoms), variable chain length and several unsaturation grades have been evaluated to estimate how the chemical nature of the acidic reagent affects the functionalization degree, OH and pH value. Reactions were carried out at temperatures higher than melting point of each acid, while the ratio carboxyl group to epoxide group was varied to obtain the maximum degree of functionalization. Step 2-Synthesis of bio-based flexible polyurethane foams (PUs): to synthesize PUs, the oleic bio-based polyol (code MB174), produced by step 1, was blended with polyol mustard oil-based (at 18.5 wt%), MDI was used as isocyanate source, water as blowing agent and catalysts and silicone surfactant to control the polymerization and blowing reactions. The chemico-physical and mechanical properties were evaluated and compared to those of a conventional flexible polyurethane foam produced by using commercial-synthetic polyol. Preliminary results showed that the addition of MB174 positively affects the mechanical properties of the produced foam.