Thermal Behavior of Zein-based Biodegradable Films
| Hlavní autori: | , , |
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| Médium: | Článok |
| Jazyk: | angličtina slovenčina |
| ISSN: | ISSN 0038-9056 |
| On-line prístup: | http://www.viks.sk/chk/star_1_03_25_29.doc |
| Abstrakt: | Summaries. In previous work, zein was plasticized with oleic acid to obtain flexible films. However, it was observed that film properties were affected by the preparation method employed. Our objective was to investigate the effect of processing methods on thermal behavior of zein films by differential scanning calorimetry (DSC). Films containing 41% oleic acid were prepared by casting ethanol solutions of its components on flat surfaces or by extrusion of zein resins prepared by cold water precipitation of ethanol solutions of zein and oleic acid. Extrusion was carried out in single-screw or twin-screw extruders. Zein films were finished by hot rolling or heated in a Carver press. DSC ther-mograms showed large oleic acid melting peaks for cast films, smaller peaks for resin films, and no apparent peaks for heat-treated samples. It was suggested that the resin formation process enhanced zein-oleic acid interactions and promoted plasticization. All samples showed glass transitions at low temperatures. Conclusions. Zein was effectively plasticized by oleic acid as evidenced by the lowered Tg of resulting films. Low temperature Tg values measured in this study were in the vicinity of those reported for other proteins at high plasticization levels. It appeared that the Gordon and Taylor equation was able to predict Tg for zein plasticized with oleic acid at 41% (w/w). That value was similar to the Tg predicted by the same equation for zein plasticized with water at 41% moisture content. Processing methods for film formation and finishing affected binding of oleic acid to zein. The resin formation process increased binding with respect to film casting. Heat treatment of extruded samples increased binding over unheated films. Thermal properties of resins were not affected by room temperature extrusion. |
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| ISSN: | ISSN 0038-9056 |
