bigler et al.[31] reported, smaller semiconductor parti- cles increased the surface area and catalytic effect and therefore nano-sized particles have better antibacter- ial activity than micron-sized particles. Furthermore, the particle content is another important factor in an- tibacterial efficiency. As seen in previous study of Wang[16], when the concentration of the nanoparti- cles increased, it became hard to control the disper- sion and the particles might mask each other during UV exposure. Therefore, insufficient UV exposure induces weak photocatalytic activity. In this study, the composites with highest concentration of TiO2 in PP/TiO2 /SEBS-g-MA/silane 5 and PP/TiO2 /silane 5 gave worst antibacterial properties as given in Ta- ble 3. In Fig. 6, the X-ray mappings of the distrib- ution of Ti element on the surface of the composite moldings having highest and lowest antibacterial effi- ciency were given. It was seen that when the particle content is low, the particles separate more homoge- nous without agglomerates.