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3.8. Thermal characteristicsThe thermal behavior of the native and OEO-included biocom-posite films was examined using DSC. Fig. 5 shows the typical DSCthermogram of films with or without essential oil. Two endothermic peaks were detected for all films. The first endothermic peakthat occurs over the temperature range of 108–114◦C may beassigned to the overlapping of different phenomena e.g., evaporation, melting and recrystallization of small and/or imperfect gelatincrystallites, and corporation of the glass transition of -amino acidblocks in the polypeptide chain (Denavi et al., 2009; Rivero et al.,2010), while the second peak in the range of 240–263◦C beingassociated with the thermal degradation of polymers. The secondendothermic peaks, represent the polymer degradation, for con-trol and 0.4% (w/v) OEO-containing films which have appearedat 261–263◦C, while these peaks have shifted to lower tempera-ture at 244–240◦C for 0.8 and 1.2% (w/v) OEO, respectively (Fig. 5).This shift may be described by the plasticizing action of oil, whichincreases the free volume within the polymer network and thesegmental mobility of the polymer chains (Sobral et al., 2001). Sim-ilar results have been found by Aliheidari et al. (2013) in sodiumcaseinate-based films containing Matricaria recutita essential oil.
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