Improvement of mechanical properties by a polydopamine interface in highly filled hierarchical composites of titanium dioxide particles and poly(vinyl butyral)

Abstract

In this work, the preparation and properties of hierarchical composites of titanium dioxide (TiO2) particles (rutile modification) and poly(vinyl butyral) (PVB) are discussed. The volume fraction of the ceramic particles was approximately 60%. Two types of composites with different fillers were examined, i.e. TiO2 particles with and without a thin coating of polydopamine (PDA). A variety of characterization methods was applied in order to analyze the properties of the particles and the composites. Infrared spectroscopy is used to verify the functionalization of the particles with a thin polydopamine layer. Thermal analysis provides information on the thermal stability and the degree of functionalization of the coated particles and the composites. Scanning electron microscopy investigations reveal that the functionalized TiO2 particles with PDA form larger agglomerates which enable the coating of the TiO2 particles with PVB via the spouted bed technique. Nanoindentation experiments show that the final hierarchical composite material with the use of non-coated TiO2 particles exhibits a hardness of 0.75 ± 0.04 GPa and a Young's modulus of 29.5 ± 1.0 GPa. The composites containing polydopamine coated TiO2 particles show an increase of approximately 40% in hardness and 25% in Young's modulus in comparison to the composites with uncoated TiO2.