Antimicrobial polymers - The antibacterial effect of photoactivated nano titanium dioxide polymer composites

To obtain a polymer with antimicrobial properties for medical and sanitary applications nanoscale titanium dioxide (TiO₂) particles have been incorporated into a medical grade polypropylene (PP) matrix with various filler contents (0 wt %, 2 wt %, 10 wt % and 15 wt %). The standard application of TiO₂ for antimicrobial efficacy is to deposit a thin TiO₂ coating on the surface. In contrast to the common way of applying a coating, TiO₂ particles were applied into the bulk polymer. With this design we want to ensure antimicrobial properties even after application of impact effects that could lead to surface defects. The filler material (Aeroxide® TiO₂ P25, Evonik) was applied via melt compounding and the compounding parameters were optimized with respect to nanoscale titanium dioxide. In a next step the effect of UV-irradiation on the compounds concerning their photocatalytic activity, which is related to the titanium dioxide amount, was investigated. The photocatalytic effect of TiO₂-PP-composites was analyzed by contact angle measurement, by methylene blue testing and by evaluation of inactivation potential for Escherichia coli (E.coli) bacteria. The dependence of antimicrobial activity on the filler content was evaluated, and on the basis of different titanium dioxide fractions adequate amounts of additives within the compounds were discussed. Specimens displayed a higher photocatalytic and also antimicrobial activity and lower contact angles with increasing titania content. The results suggest that the presence of titania embedded in the PP matrix leads to a surface change and a photocatalytic effect with bacteria killing result.