Submitted to: Polymers and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2009
Publication Date: 8/28/2009
Citation: Woods, K.K., Selling, G.W., Cooke, P.H. 2009. Compatible Blends of Zein and Polyvinylpyrrolidone. Journal of Biobased Materials and Bioenergy. Available online http://www.springerlink.com/content/q806776x453k1335/fulltext.pdf
Interpretive Summary: Interest in biodegradable plastics and films has increased significantly due to environmental concerns. One potentially attractive component of such plastics is zein, the predominant prolamine found in corn. Zein is one of the main co-products of the bioethanol industry, as it is a major fraction of both corn gluten meal (wet milling) and distillers dried grains (dry milling). It has historically been used predominantly in the coatings and textile industries. The abundance of bioethanol co-products has created renewed interest in zein as a potential bioplastic. In order to better utilize zein in commercial applications, an improvement in physical properties such as moisture sensitivity is desired. One way to improve the properties of a given polymer is to blend it with another polymer. The main challenge in the preparation of polymer blends lies in the selection of compatible polymers. While some compatible polymer blends do exist, most polymer combinations do not form completely miscible blends. Zein has previously been blended with starch, polycaprolactone, and methyl- and acetylcellulose, and all of these combinations formed immiscible blends that led to deficient properties. In an effort to improve the tensile properties of zein films, we have blended zein with the synthetic polymer polyvinylpyrrolidone and found that the resulting films had improved properties. This is the first extensive study of a compatible blend of zein with a synthetic polymer. This research will benefit the bioethanol industry by improving the marketability of a major co-product of this industry and therefore making the entire process more profitable.
Technical Abstract: Blends of zein and polyvinylpyrrolidone (PVP) were compared based on their tensile properties, thermal properties and morphology. Zein was blended with polyvinylpyrrolidone of varying molecular weights (10,000, 55,000 and 1,300,000 MW) and films were cast from ethanol solutions. Films cast using the higher molecular weight polymers showed an improvement in tensile strength, up to a 24% increase, compared to control. Differential scanning calorimetry data for the blends showed single Tm and Tg values of an intermediate value between those of zein and PVP control samples. Field emission scanning electron microscopy images show no obvious inhomogeneities, and confocal fluorescence microscopy showed no decreased uniformity in the PVP/zein films compared to control. IR results also suggest the presence of a compatible blend. Electrospun fibers of the zein/PVP blends were also obtained. These findings suggest that zein and polyvinylpyrrolidone combine to form a compatible blend, the first extensive study of such a blend of zein with a synthetic polymer.