Dynamic Mechanical Behavior and Thermal Characterization of Biofilms Based on Starch Modified by Fungi Isolates
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Starches modified by Ophiostoma spp. have been investigated to develop bio-materials with enhanced mechanical and physical properties for thermoplastic applications. In this study, glass transition temperature (Tg) of modified starches was investigated in both dynamic mechanical analyzer (DMA) and differential scanning calorimeter (DSC) to detect molecular changes in the starch’s structure. Overall, two thermal transitions were observed in modified starches, as opposed to one in their native counterparts. Scanning electron microscopy of granular modified starch indicated visible damages and internal structural perturbations in addition to occlusion of granular pores by extraneous materials owing to possible enzymatic degradation and production of secondary metabolites. Modified starches registered two-fold improvement in storage modulus as compared to that of native starches. From the study of second derivative of the mass loss against temperature, two thermal transitions were also identified in modified starches. X-ray diffraction analyses showed that crystalline regions of the starch granules remained intact after the modification. It is proposed that the second phase transition potentially corresponds to modified amylose fractions and/or exopolysaccharides produced by the fungi.
KeywordsExopolysaccharide Glass transition Starch gelatinization Differential thermal analysis Dynamic mechanical analysis Crystallinity
The authors gratefully acknowledge to the National Council on Science and Technology (CONACYT), Mexico, BioCorp Canada Foundation and Natural Sciences and Engineering Research Council of Canada (NSERC) strategic grant for financial support of this study.
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