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Bioderived polyurethane foams based on tung oil: synthesis and characterization
G. SOTO; N. E. MARCOVICH; M. A. MOSIEWICKI
Simposio; BALTIC POLYMER SYMPOSIUM; 2015
Flexible polyurethane foams (FP) belongs to a well-known class of polymeric materials that offers daily applications like cushioning and automotive seating, among others. Nowadays, the global production of FP uses polyols mainly derived from petrochemical raw materials. Consequently, the replacement of these components by more eco-friendly materials is challenging. In this sense, the chemical modification of vegetable oils is a promising alternative in the production of green polyols1. Tung oil, a non-edible oil also called ?China wood oil? is commonly used in wood finishing applications because of its drying properties. These properties are associated to its composition, due to its high content of unsaturated fatty acids. In particular, -eleostearic acid, a fatty acid with three-conjugated double bonds accounts for around the 80% of the triglyceride composition of the tung oil. Through the chemical modification of tung oil it can be obtained multi-functional polyols, which can be used further as building blocks in the bio-based polyurethane synthesis. In this work, hydroxylated methyl esters (HMETO) and glycerol were obtained as main and sub products, respectively, of tung oil chemical modification, following a two-step procedure. First, fatty acid methyl esters (FAME) and glycerol (GLY) were obtained by means of alkaline transesterification. Then, the resultant FAME was modified by hydroxylation with performic acid generated in situ. In this way, hydroxyl groups (-OH) were added to the carbon chain. Infrared spectroscopy (FTIR), proton nuclear magnetic resonance (H1NMR) and different analytical procedures (iodine value, acid value and hydroxyl number) were used to characterize the tung oil and reaction products. The hydroxyl value of the HMETO was 163.2 mg KOH/g.Polyurethane foams were based on a commercial polyether polyol and variable amounts of glycerol or hydroxylated methyl ester of tung oil (0, 10, 20 wt.% respect to the polyether polyol mass) as multifunctional bio-based polyols. The petroleum-based polyol presents low functionality (3) and high molecular weight (4800), as required for flexible foam. Water was chosen as chemical blowing agent and a multifunctional pre-polymer based on 4,4?-diphenylmethane diisocyanate (pMDI) with an equivalent weight of 133 g/eq was used as the isocyanate component.The characterization of these foams, achieved by measuring the characteristic times during reaction and by termogravimetric analysis (TGA), scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and density measurements performed on the cured flexible foams, is reported and discussed. In brief, it was found that the obtained foams are not only a good alternative for applications where low weight, flexibility and insulating properties are desirable but also are more eco-friendly than the control foam prepared by using just the petroleum-based polyol.References1.Ribeiro da Silva V., Mosiewicki M. A., Yoshida M. I., Coelho da Silva M., Stefani P. M. and Marcovich N. E. Polyurethane foams based on modified tung oil and reinforced with rice husk ashes I: Synthesis and physical chemical characterization // Polymer Testing ? 2013 ? Vol. 32 ?P. 438-445.