Heat sealing capacity of native and acetylated corn starch based films was evaluated to develop biodegradable packages, such as bags. Thermo-mechanical properties were analyzed since they condition their handling and applications. Acetylated starch addition reinforced 80% sealing resistance of starch films. Unplasticized heat-sealed films presented adhesive failures while those containing glycerol showed a rupture near the zip. Unplasticized films exhibited a single relaxation (at around 60 degrees C), detected by DMA and conventional DSC, which was not affected by the acetylated starch content. DMA curves of plasticized films showed two relaxations, one close to -50 degrees C associated to the glass transition of the plasticizer-rich phase, and other around 60 degrees C, attributed to the starch-rich phase. This last transition was also observed using MTDSC. Glycerol addition decreased the relaxation temperature of the starch-rich phase being this effect more marked in native starch films, about 28%. A relation between film composition, microstructure, mechanical behavior, and dynamic mechanical thermal analysis was established. (C) 2011 Elsevier Ltd. All rights reserved.