Effects of filler-matrix morphology on mechanical properties of corn starch-zein thermo-moulded films

The effects of filler-matrix morphology on mechanical behaviour of thermo-moulded films based on native or amorphous corn starch as matrix, and zein (sizes of <100, <250, and >500 μm) as filler were investigated. The morphology and mechanical behaviour were characterized by Confocal Light Scanning Microscopy and three point bending test, respectively. For native starch blends, the zein network was relatively dense when initial zein size increased from 100 to 500 μm. However, small initial zein size favored continuous morphology for amorphous starch blends. It is noted that the stress at rupture values of native starch blends decreased when zein size increased, indicating relatively compact zein network damaged the stress of starch matrix. On the contrary, the variations of the stress at rupture values of amorphous starch blends were not significantly different, attributing to the heterogeneous morphology of incomplete zein network dispersed in the amorphous starch matrix.