Bio-derived polyurethane foams based on tung oil: synthesis and characterization

SOTO, GUILLERMO D.; MARCOVICH, NORMA E.; MOSIEWICKI, MIRNA A.

Sigulda

Simposio; Baltic Polymer Symposium 2015; 2015

Riga Technical University - Institute of Polymer Materials

Flexible polyurethane foams (FP) belongs to awell-known class of polymeric materials that offers daily applications likecushioning and automotive seating, among others. Nowadays, the globalproduction of FP uses polyols mainly derived from petrochemical raw materials.Consequently, the replacement of these components by more eco-friendlymaterials is challenging. In this sense, the chemical modification of vegetableoils is a promising alternative in the production of green polyols1.Tung oil, a non-edible oil also called ?Chinawood oil? is commonly used in wood finishing applications because of its dryingproperties. These properties are associated to its composition, due to its highcontent of unsaturated fatty acids. In particular, a-eleostearic acid, a fatty acid withthree-conjugated double bonds accounts for around the 80% of the triglyceridecomposition of the tung oil. Through the chemical modification of tung oil itcan be obtained multi-functional polyols, which can be used further as buildingblocks in the bio-based polyurethane synthesis. In this work, hydroxylatedmethyl esters (HMETO) and glycerol were obtained as main and sub products,respectively, of tung oil chemical modification, following a two-stepprocedure. First, fatty acid methyl esters (FAME) and glycerol (GLY) wereobtained by means of alkaline transesterification. Then, the resultant FAME wasmodified by hydroxylation with performic acid generated in situ. In this way, hydroxyl groups (-OH) were added to thecarbon chain. Infrared spectroscopy (FTIR), proton nuclearmagnetic resonance (H1NMR) and different analytical procedures(iodine value, acid value and hydroxyl number) were used to characterize thetung oil and reaction products. The hydroxyl value of the HMETO was 163.2 mgKOH/g.Polyurethane foams were based on a commercialpolyether polyol and variable amounts of glycerol or hydroxylated methyl esterof tung oil (0, 10, 20 wt.% respect to the polyether polyol mass) asmultifunctional bio-based polyols. The petroleum-based polyol presents lowfunctionality (3) and high molecular weight (4800), as required for flexiblefoam. Water was chosen as chemical blowing agent and a multifunctionalpre-polymer based on 4,4?-diphenylmethane diisocyanate (pMDI) with anequivalent weight of 133 g/eq was used as the isocyanate component. The characterization of these foams, achievedby measuring the characteristic times during reaction and by termogravimetricanalysis (TGA), scanning electronic microscopy (SEM), Fourier transforminfrared spectroscopy (FTIR) and density measurements performed on the curedflexible foams, is reported and discussed. In brief, it was found that the obtained foams arenot only a good alternative for applications where low weight, flexibility andinsulating properties are desirable but also are more eco-friendly than thecontrol 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.