Aims: To develop novel polypropylene composite materials with antimicrobial activity by adding different types of copper nanoparticles.

Methods and results: Copper metal (CuP) and copper oxide nanoparticles (CuOP) were embedded in a polypropylene (PP) matrix. These composites present strong antimicrobial behaviour against E. coli that depends on the contact time between the sample and the bacteria. After just 4 h of contact, these samples are able to kill more than 95% of the bacteria. CuOP fillers are much more effective eliminating bacteria than CuP fillers, showing that the antimicrobial property further depends on the type of copper particle. Cu²⁺ released from the bulk of the composite is responsible for this behaviour. Moreover, PP/CuOP composites present a higher release rate than PP/CuP composites in a short time, explaining the antimicrobial tendency.

Conclusions: Polypropylene composites based on copper nanoparticles can kill E. coli bacteria depending on the release rate of Cu²⁺ from the bulk of the material. CuOP are more effective as antimicrobial filler than CuP.

Significance and impact of the study: Our findings open up novel applications of these ion-copper-delivery plastic materials based on PP with embedded copper nanoparticles with great potential as antimicrobial agents.