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Development of Biodegradable Gluten-PLA Laminate Films

Sung-Woo Cho and Mikael S. Hedenqvist. Fiber and Polymer Technology, Royal Institute of Technology, Teknikringen 56-58, Stockholm, 100-44, Sweden

The research interest in the use of natural biomaterials, alternatives to synthetic polymers, has increased with respect to environmental concerns. Several studies, however, have reported that plasticizer migration from biobased films including wheat gluten (WG) causes deterioration of mechanical and barrier properties with time. Also, their high water sensitivity compromises potential applications as packaging materials. For these reasons, laminate films consisting of a WG layer and polylactic acid (PLA) layers were developed by compression molding processes with the aims to limit the effects of aging and to improve the barrier properties, especially against moisture. WG films with different glycerol contents (0, 5, 10, 20 and 30 wt%) were pressed at 110 and 130 C for 10 min. FT-IR revealed in the intense amide-I region that thermo-forming temperatures led to different degrees of protein aggregation and polymerization. The lamination of WG and PLA layers was performed at 110 C. Scanning electron microscopy showed that the laminated films were uniform in thickness. The glycerol contents in WG layer had significant effect on tensile properties and bending stiffness of laminates. And the adhesion between WG and PLA layers increased with higher glycerol content. The laminates were very effective to enhance oxygen and moisture barrier. Moreover, the mass loss of these films on a porous paper was not observed during the four-month period and it is assumed that no change in the glycerol content played a key role in maintaining the integrity and properties of the laminates.