Thiol-functionalized copper nanoparticles as antibacterial additives for polypropylene

This study investigates the development of antibacterial polypropylene (PP) composites through the incorporation of thiol-functionalized copper nanoparticles (CuNPs–SH) as active additives. The objective was to evaluate the functional performance of the system, with particular emphasis on verifying copper ion release as the active mechanism and its direct relationship with the antibacterial response of the composite material. CuNPs–SH were synthesized and characterized using ultraviolet–visible spectroscopy, X-ray diffraction, and thermogravimetric analysis, along with ion release studies in aqueous medium. The release results show an initial increase in Cu²⁺ ion concentration followed by stabilization over time, indicating a controlled availability of active species. In addition, thermogravimetric analysis confirms the thermal stability of the additive within the temperature range used for PP processing. Subsequently, CuNPs–SH were incorporated into the PP matrix at 10 wt% through melt compounding. X-ray diffraction analysis indicates that the incorporation of the additive does not alter the crystalline structure of the polymer within the detection limits of the technique. The antibacterial performance of the composite, evaluated against Escherichia coli under ISO 22196, showed an approximate reduction of 40.8%, corresponding to a logarithmic reduction of 0.23. These results demonstrate that thiol-functionalized copper nanoparticles can be used as antibacterial additives in PP, representing a novel strategy for the development of functional polymer composites with controlled antibacterial activity.