Effect of hydrothermally synthesized titanium nanotubes on the behaviour of polypropylene for antimicrobial applications

TiO₂ nanotubes (TiO₂-Ntbs) synthesized by a hydrothermal method were used as filler to prepare polypropylene (PP) composites by melt blending. Their structural properties as well as their biocidal potential were studied. Nanotubes were used either as-synthesized or organically modified with hexadecyltrimethoxysilane (Mod-TiO₂). These nanoparticles form secondary structures with sizes around 100 nm that are well dispersed in the polymer matrix, but not homogeneously because agglomerates larger than 1 μm are also seen by transmission electron microscopy. Regarding the properties of the composites, the incorporation of the nanoparticles increased the polymer's crystallinity and thermal stability. The maximum decomposition temperature of the matrix increased by ca 13 °C compared to virgin PP. The nanotubes further increase the spherulite nucleation density, and therefore a reduction in the diameter of spherulites and an increase in their number were observed. Despite the above, the addition of TiO₂ nanoparticles did not modify the mechanical properties of PP. The PP/TiO₂-Ntb nanocomposites exposed to UVA radiation showed a biocidal behaviour, reducing a colony of Escherichia coli by 81%.