The TPS mechanical properties depend on the temperature
of starch processing, water content as well as quantity
and type of added plasticizers and aid materials. Increase
of the plasticizer content brings about a decrease in tensile
strength of TPS; whereas, the elongation at break increases.
Starch is a natural polymer containing numerous hydrogen
bonds between the hydroxyl radicals in its molecules; therefore
it manifests substantial tensile strength values. Glycerol,
sorbitol or glycol behave like diluents and decrease the interaction
between molecules and consequently, they diminish
tensile strength. At the same time, they act as placticizers that
improve macromolecular mobility and leads to a rise in elongation
at break (Liu et al., 2001; Shogren, 1993; Yu et al., 1998).
Addition of filler materials like cellulose fibres, flax, kaolin or
pectin increases the tensile strength but decreases the elongation
at break. In turn, urea or boric acid addition improves
the elongation at break but decreases the tensile strength