Effect of Glycerin and Starch Crosslinking on Molecular Compatibility of Biodegradable Poly(lactic acid)-Starch Composites |
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Authors: | Xue Shen Wu |
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Institution: | (1) Institute of Molecular Medicine, Huaqiao University, 362021 Quanzhou, Fujian Province, China;(2) Present address: 310 Tibet Avenue, Savannah, GA 31406, USA |
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Abstract: | Poly(lactic acid) (PLA) is a biodegradable material. However, PLA is relatively cost effective. Blending starch with PLA is
one of the promising efforts because starch is a widely distributed and inexpensive product. PLA and starch were blended using
a rheometer to form composites in this report. Glycerin was added into the blends to make the mixture molecular compatible
and more homogeneous. The starch was crosslinked using epichlorohydrin to improve the compatibility of starch with PLA. Two
series of composite were fabricated. One was PLA and the crosslinked starch containing 32 wt% glycerin. In this group, the
crosslinking degree of the modified starch was varied. The second group was PLA and non-crosslinked starch with varied amount
of glycerin added. Micro-structure of the blending composites was observed using a SEM to view the homogeneity of the mixture.
The SEM pictures indicated that the compatibility of PLA and starch molecules was poor. The addition of glycerin can change
the compatibility of PLA and starch. The higher the glycerin content in the composites, the better the compatibility between
PLA and starch. Furthermore, when the starch was crosslinked by epichlorohydrin, the compatibility of PLA and starch can be
greatly improved. The compatibility increases with the increase of crosslinking degree. This is due to the change of hydrophilicity
of starch because the hydroxyl groups on the starch molecules were crosslinked into ether groups by the epichlorohydrin molecules. |
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