Preparation of zein-based biodegradable materials and investigation of their physical properties

Zein, the prolamine in corn, was investigated as a base material for preparation of biodegradable sheets and films in this study. Zein-based moldable resins could be obtained by plasticizing the protein with fatty acids. Plasticization could be performed by co-melting zein and fatty acids in a microwave oven or dissolving zein and fatty acids in a common solvent followed by precipitation and kneading. Control of processing temperature and mechanical treatments were found crucial in the resin developing process. The resulting resins were able to be formed into sheets, films or objects of varied geometry illustrating their potentiality as thermoplastic materials.; Plasticization of zein with palmitic or stearic acid by the microwave co-melting process increased the plasticity of sheets. However, the plasticization was limited due to the high melting points of palmitic and stearic acids and the incomplete mixing of the short processing time. Microscopy examination of sheet samples showed the development of layered structure as fatty acid content increased. Zein-fatty acid layers were believed to be responsible for the increased tensile strength of plasticized zein sheets and to have contributed to their increased resistance to water absorption.; Plasticization was improved by dissolving zein and fatty acids in warm aqueous alcohol solutions. Resins were obtained through precipitation and kneading treatments. Inclusion of palmitic and stearic acid in the formulation resulted in harder resins that were suited for rolling into sheets; whereas plasticization with oleic or linoleic acid gave a softer resin that could be stretched into thin films. Films were found to be a matrix of zein fibrils. Coating sheets and films with heated flax oil not only improved the water resistance but also the tensile properties of films.