Polyurethanes |
Polyurethanes | Elastomers New Biobased Polyurethane from Lignin and Soy Polyols M. Özgür Seydibeyoğlu Manjusri Misra Amar Mohanty Bioproducts Discovery & Development Centre Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada Figure 1: Lignin Particles (Electron Microscopy Images) Lignin being the second most abundant polymer in the world is undervalued which is a by-product in the pulppaper and lignocellulosic industries [1]. Lignin with high e-modulus value (5-6.7 GPa) offers many new materials as a polymer and as a reinforcing phase. Lignin particles are shown in Figure 1 (Electron microscopy Hitachi S-570 at 10 kV). On the other side, biobased polyurethane materials take a lot of attention to replace petroleum based polyurethanes (Figure 2 showing lignin incorporated polyurethane structure) [4]. Polyurethane has two important components, the isocyanate and the polyol. These two reactants have many different forms creating a wealth of different of products and applications. Recent research is focused on replacing petroleum based polyol with plant based polyols [5-7]. One of the most commonly used polyol is the castor oil due its high hydroxyl numbers [6]. Another commonly used soy polyol is obtained from soybean oils. However the use of soy polyol based polyurethanes is limited due to lower mechanical properties. There are studies to reinforce biobased polyurethanes with glass fibers and hemp fibers to overcome the low mechanical properties [8, 9]. In this study, lignin was used as reinforcement for soy polyol based polyurethanes. The lignin (Protobind 2400 from ALM Private Limited, Hoshiarpur, Punjab, India) with a hydroxyl value of 400 mg KOH/g was blended with soy polyol with hydroxyl value of 166 mg KOH/g. Afterwards, the polyol blend was reacted with different isocyanates at 150ºC and cured for 8 hours. Three different isocyanates were used from Huntsman Chemicals, PMDI (polymeric diphenyl methane diisocyanate (pMDI, Rubinate M)), MDI (diphenyl methane diisocyanate, Rubinate 9511), and modified MDI (Rubinate 9271). Tensile testing was done to understand the ultimate strength, e-modulus and percent elongation of the materials synthesized. The lignin was incorporated at 5 wt % in soy polyol based polyurethanes prepared with three different isocyanates. For all the polyurethanes, the lignin showed reinforcing effect. The tensile strength was improved by 70%, 57%, and 118% for PMDI, MDI, and MMDI based polyurethanes respectively. The percent elongation values were 13.50%, 87.30%, and 105.00% respectively. Figure 3a and Figure 3b shows two different polyurethanes obtained with lignin and soy polyol reacted with different isocyanates representing different elongation values obtained. 42 bioplastics MAGAZINE [05/10] Vol. 5
Polyurethanes | Elastomers Figure 3: Biobased Polyurethane with Lignin (left stiff type, right elastic type) The lignin had significant effect for the improvement of modulus of elasticity (E-modulus) value of these biobased materials. For the PMDI based polyurethane, lignin incorporation at 5 wt % increased the E-modulus values around 12 fold. For the MMDI based polyurethane, the increase in the E-modulus values was 37 fold with the addition of 5 wt % lignin. In this study, it was shown that a new biobased polymer with various properties can be synthesized with polyols obtained from soybean oil and lignin. The biobased material has biological material content of 67.4 % and this group of polymers can find numerous applications. This discovery will enable wide usage of soy and other plant based polyols in the polyurethane materials due to reinforced properties. The most important aspect of these findings is to find new applications for lignins. Lignins are generally produced as a side product and they are mostly burned and used as energy source at a low price. By this way, new value added products can be manufactured from lignin with reinforcing the soy polyol based polyurethanes. It is reported that these new value added products from lignin (price increasing from 0 to 00 per ton) helps to decrease the price of bioethanol by creating new economic value [1]. References [1] M.N.S. Kumar, A.K. Mohanty, L. Erickson, M. Misra, J. Biobased Mater. Bioenergy 3, 1 (2009). [2] W. J. Cousins, R. W. Armstrong,W. H. Robinson, J. Mater. Sci. 10, 1655 (1975). [3] T. Elder, Biomacromolecules 8, 3619 (2007). [4] S. Husic, I. Javni, Z.S. Petrovic, Compos. Sci. Technol. 65, 19 (2005). [5] Sharma,V.; Kundu, P.P.; Prog. Polym. Sci. 33, 1199 (2008). [6] Güner, F.S.; Yağcı, Y.; Erciyes, A.T.; Prog. Polym. Sci. 31, 633 (2006). [7] G. Oertel. Polyurethane Handbook, Hanser Gardner Publications; (1994), p1. [8] J.P. Latere Dwan’Isa, A.K. Mohanty, M. Misra, L.T. Drzal, M. Kazemizadeh, J. Mater. Sci. 39, 2081 (2004). [9] J.P. Latere Dwan’Isa, A.K. Mohanty, M. Misra, L.T. Drzal, M. Kazemizadeh J. Mater. Sci. 2004, 39, 1887. Acknowledgements The authors are thankful to the Ministry of Research and Innovation (MRI) of Ontario, Canada for the post-doctoral research fellowship. Financial support from NSERC-Discovery Grants program individual (Mohanty) is greatly appreciated. Arkema is acknowledged for donations of soy polyols. H H H O H H C N C N C O C C O H H H H Isocyanate group Polyol group R 1 R 2 OH Lignin group Figure 2: Biobased Polyurethane Chemical Structure with Lignin Incorporated bioplastics MAGAZINE [05/10] Vol. 5 43
