Starch Nanocomposite and Nanoparticles: Biomedical Applications - Modern Trends in Chemistry and Chemical Engineering - page 67

and mechanical properties of TPS/PCL blend are varied with its composition and the
content of plasticizer (Table 3.2). As can be seen, TPS/PCL blend is similar to TPS/
PLA blend in both the compatibility and the role of components.

Table 3.2. Thermal and mechanical properties of thermoplastic starch/polylactide (TPS/PCL) blends.
Content of TPS [wt%] T g [°C] Tensile Strength [MPa] Elongation at Break [%]

PCL TPS
100 (TPS1) a - 8.4 3.3 126.0
75 (TPS1) 31.0 5.9 62.6
100 (TPS2) a - 43.4 21.4 3.8
75 (TPS2) 41 10.5 2.0
60 (TPS2) NF b 9.0 2.4
0 -61.5 - 14.2 >550.0
a the content of glycerol and water in TPS1 and PTS2 are 18 and 12, 10 and 16 wt% respectively
b Tg value is not found in the literature

The PCL/starch blends can be further reinforced with fi ber and nano-clay, respec-
tively. Moreover, the other properties of the blends such as hydrolytic stability, degrada-
tion rate, and compatibilization between PCL and starch are also improved. PVA is
a synthetic water-soluble and biodegradable polymer. PVA has excellent mechanical
properties and compatibility with starch. PVA/starch blend is assumed to be biodegrad-
able since both components are biodegradable in various microbial environments. The
biodegradability of blends consisting of starch, PVA, glycerol, and urea is performed
by bacteria and fungi isolated from the activated sludge of a municipal sewage plant
and landfi ll, which indicate that microorganisms consumed starch and the amorphous
region of PVA as well as the plasticizers. Meanwhile, the blend is expected to exhibit
good mechanical and process properties. Owing to the strong interaction among hy-
droxyl groups on PVA and starch chains, all the Tg of the starch/PVA blends of dif-
ferent compositions are lower than that of PVA. The excellent compatibility of two
components make the tensile strength of the blend increases with increasing PVA con-
centration, and the elongation at break of the blend is almost kept constant [110-123].
In addition, PVA can be used to enhance the compatibility of starch/PLA blends.
Because both starch and PVA are polyols, starch will form continuous phase with PVA
during blending. As a result, the mechanical properties of the starch/PLA blends are
improved in the presence of PVA. As for the blend system without PVA, starch acts as
fi ller in the PLA continuous matrix. PLA acts as the main load-bearing phase because
of the weak interaction between starch and PLA.

Blend with biopolymers
Natural polymers such as chitosan and cellulose and their derivatives are inherently
biodegradable, and exhibit unique properties. A number of investigations have been
devoted to study the blend of them with starch. Starch and chitosan are abundant