Chemistry Reference
In-Depth Information
gels are both pseudoplastic and thixotropic with greater storage stability. Their water
binding ability can provide body and texture to food stuffs and can be used as a fat re-
placement. Many functional derivatives of starch are marketed including cross-linked,
oxidized, acetylated, hydroxypropylated, and partially hydrolyzed material.
Hydrolysis of starch, usually by enzymatic reactions, produces a syrupy liquid
consisting largely of glucose. It is widely used to soften texture, add volume, inhibit
crystallization, and enhance the fl avor of foods. Nowadays starch-based fi lms are used
for food packging, a coating for tablets or capsules. Starch nanoparticles and mic-
roparticles were used for the release of drugs, cosmetics, and aromas, and so forth.
STARCH NANOCOMPOSITES
Thermoplastic Cassava Starch/Sorbitol-modified Montmorillonite
Nanocomposites Blended with Low Density Polyethylene
One of today's serious global problems is the management of the steadily increasing
amount of solid waste. Tremendous quantities of polymers, mainly polyolefins (e.g.,
polyethylene, polypropylene) are produced and discarded into the environment, end-
ing up as wastes that do not degrade spontaneously.
Some polymer products have a short useful life, in many cases of less than 2 years.
They are consumed and discarded into the environment when their utilization ceases.
The petroleum-based polymers were developed for durability and resistance to all
forms of degradation. With developing environmental ecological awareness, biode-
gradable plastics are proposed as one of many strategies to alleviate the environmental
impact of petroleum-based plastics and are gaining public interest. They are designed
to be easily degraded by the enzymatic action of living microorganisms such as bac-
teria, yeasts, and fungi. In contrast to synthetic polymers, natural polymers are good
base materials for producing inexpensive, rapid degradable plastics. The use of bio-
degradable materials based on renewable resources can help reduce the percentage
of plastics in industrial and household wastes. Therefore, several considerable efforts
have been made to accelerate the biodegradability of polymeric materials by replac-
ing some or all of the synthetic polymers with natural polymers in many applications
in order to minimize the environmental problems caused by plastic wastes. Starch is
one of the main natural polymers used in the production of biodegradable materials
because of its renewability, biodegradability, wide availability, and low cost. How-
ever, the starch presents some drawbacks, such as the strong hydrophilic behavior
and poorer mechanical properties when compared to synthetic polymers. It is pre-
dominantly water-soluble and cannot be processed by melt-based routes because it
decomposes before melting. To improve the mechanical and barrier properties of the
starch composites at the same time, a small amount of inorganic nanofi llers is com-
monly added to a polymer matrix. The clay, montmorillonite (MMT), is one of the
attractive nanofi llers utilized due to its high aspect ratio of width/thickness, in an or-
der of 10-1000. Indeed, for very low amounts of nanoparticles, the total interface
between polymer and silicate layers is much greater than that in conventional com-
posites. In general, the clay needs to be modifi ed in order to enlarge the interlayer dis-
tance. Ma, et al. prepared sorbitol-modifi ed montmorillonite, which was added into the
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