ABSTRACT
The formation of starch nanocomposites is an emerging
field. The addition of an appropriate nanoclay such as nat-
ural kaolonite, hectorite, Na-Cloisite (MMT), and organi-
cally modified MMT to a starch-biopolymer blend matrix
can increase the physical, mechanical, and thermal proper-
ties of the polymer (blends).[6] The difference between
nanoclays and more commonly used fillers, e.g., calcium
carbonate, is that the layered silicate in the nanoclays can be
dispersed into very thin (10 A˚) and individual layers.[7]
Chemical Modification
Chemical modification refers to the introduction of func-
tional groups (ether and esters) into starch molecules to
modify the structure and properties of native starch.[8] The
incorporated ether and ester groups act like internal plasti-
cizers, resulting in modified starches that behave like ther-
moplastics.[9] Moreover, the modifications improve the
miscibilities of starch and other hydrophobic-synthetic poly-
mers. Of the modified starches, hydroxypropylated starch,
with a low level of substitution, has been used widely in the
production of commercial packaging materials. Starch acet-
ates can be hydrophilic to very hydrophobic, depending on
their degree of substitution. The more highly substituted
they are, the more functional they are in most packaging
applications.[10] However, the more highly substituted they
are, the more costly they are. Currently, they are not cost-
competitive with synthetic polymers.
