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

Composites of thermoplastic starch (TPS) with titanium dioxide particles (mTiO2; average size 0.1 μm) 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 3 wt.% 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.