Properties and Biodegradation of Thermoplastic Starch Obtained from Grafted Starches with Poly(lactic acid)
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Properties and biodegradation of thermoplastic starch obtained using granular starches grafted with poly(lactic acid) (St-g-PLA) were studied. The grafting of PLA on the starch granule was verified by the emergence of the carbonyl group in the FTIR spectra and the higher diameter of the grafted starch granule. Thermoplastic starch from ungrafted granular starch (TPS) and grafted granular starch (TPGS) were obtained by mixing ungrafted or grafted starch with water, glycerol or sorbitol in a mixer. TPS and TPGS behave as plastic materials, and their mechanical properties depend on the type of plasticizer used. Materials with glycerol as the plasticizer exhibited less rigidity than the materials obtained using sorbitol. The presence of starch-g-PLA results in an increase in the elongation of the thermoplastic material. TPS and TPGS were hydrolysed by amylolytic enzymes in short-time periods compared to granular PLA-grafted starches.
KeywordsGrafted starch Poly(lactic acid) Thermoplastic starch Mechanical properties Enzymatic degradation
The authors wish to thank the National Council of Science and Technology in México (CONACyT) for financial support of the Ph.D. thesis of one of the authors (Cuevas-Carballo, Z. B.). The X-ray diffraction analysis was performed at the National Laboratory of Nano and Biomaterials (financed by Fomix-Yucatán and CONACyT), CINVESTAV-IPN. Mérida Unit. We thank Dr. Patricia Quintana for access to LANNBIO and M. C. Daniel Aguilar for technical support in obtaining the diffractograms.
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