Thermoplastic starch composites with TiO₂ particles: Preparation, morphology, rheology and mechanical properties

Composites of thermoplastic starch (TPS) with titanium dioxide particles (mTiO₂; average size 0.1μm) with very homogeneous matrix and well-dispersed filler were prepared by a two-step method, including solution casting (SC) followed by melt mixing (MM). Light and scanning electron microscopy confirmed that only the two-step procedure (SC+MM) resulted in ideally homogeneous TPS/mTiO₂ systems. The composites prepared by single-step MM contained non-plasticized starch granules and the composites prepared by single-step SC suffered from mTiO₂ agglomeration. Dynamic mechanical measurements showed an increase modulus with increasing filler concentration. In TPS containing 3wt.% of mTiO₂ the stiffness was enhanced by >40%. Further experiments revealed that the recommended addition of chitosan or the exchange of mTiO₂ for anisometric titanate nanotubes with high aspect ratio did not improve the properties of the composites.