This manuscript presents experimental studies of composite materials based on poly (L lactic acid) (PLLA) and poly (3-hydroxybutyrate) (PHB) matrices filled with electrolytic copper powder, having a very high dendritic structure. Volume fractions of the copper powder used as filler in all prepared composites were varied in the range 0.5-6.0 vol.%. Samples were prepared by hot moulding injection at 170 °C. Influence of particle size and morphology, as well as the influence of matrix type on conductivity and percolation threshold of the obtained composites were examined. Characterization included: electrical conductivity measurements using AC impedance spectroscopy (IS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Fourier-transform Infrared spectroscopy (FTIR). Presence of three-dimensional conductive pathways was confirmed. The obtained percolation thresholds of 2.83 vol.% for PLLA and 3.13 vol.% for PHB composites were measured, which is about three times lower than the ones stated in the literature for similar composites. This property is ascribed to different morphologies of the filler used in the present investigation.
The application of self-cleaning coatings presents one of the most effective ways to protect the surfaces of the building materials. The effect of TiO2/kaolin based coatings applied to three types of substrates: non-porous, porous and highly porous, was investigated. Mechanical activation was applied for the impregnation of the active TiO2 component (in content of 3 and 10 wt. %) into the kaolin support. Surface properties (roughness, hydrophilicity and micro-hardness) and functional properties (photocatalytic activity and self-cleaning efficiency) were studied in order to define the optimal formulation of the applied coatings. The effect of the photocatalytic behavior of the coated substrates in terms of self-cleaning ability was assessed by the photodegradation of Rhodamine B, performed before and after durability tests. The results obtained in this paper showed that photocatalytic activity of the TiO2/kaolin composite coating generally depends on the procedure of TiO2 impregnation into the kaolin clay and the loaded TiO2 content.
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