Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2012
Publication Date: 8/7/2012
Citation: Sessa, D.J., Cheng, H.N., Kim, S., Selling, G.W., Biswas, A. 2012. Zein-based polymers formed by modifications with isocyanates. Industrial Crops and Products. 43(1):106-113.
Interpretive Summary: Production of bioplastics in 2011 will top one million tons in 2011 and will double in size by 2015 according to the European Bioplastics Industry. Zein, a protein co-product of the ethanol industry, has great potential for use in the bioplastics industry. Reaction of zein with isocyanates to generate bioplastics is a relatively new area of research. Our current investigation explores the reactivity of isocyanates and diisocyanates with the zein's many potential reactive sites to derive products with improved water resistance. The complex reaction chemistries involved were explored using various analytical techniques providing information basic to the construction of new polymer composites for the industrial market place. Our research findings to derive zein-based polymers will not only benefit the farmer and corn ethanol industry but also the multi-billion dollar thermoplastics industries.
Technical Abstract: Zein is a prolamine protein found in corn and a promising industrial bioplastic. However, for zein to reach its full commercial potential, research must find ways to overcome two main problems: its relatively high cost and its poor resistance to water. In this work, we have modified zein with several isocyanates and diisocyanates. The major reaction pathways have been identified with the help of NMR. For all the isocyanates employed, the surface free energy of the modified zein has decreased, indicating decreased hydrophilicity. The moisture uptake also appears to decrease with isocyanate modification. As expected, the reaction with diisocyanate partly increases the molecular weight of zein. DSC data show single glass transition temperatures in all cases. The mechanical properties of modified zein are either similar to unmodified zein or reduced in some cases. An attempt has also been made to carry out isocyanate reactions on the surface of zein films.