Strategies to preserve bio-based antimicrobial agents during extrusion and injection molding

The reduction of bacteria-caused disease transmission gains importance in medicine as well as in areas of public life. As part of a project, a bio-based compound was developed which combines the advantages of plastics processing and the natural bactericidal effect of heartwood. A Polylactide polymer and bactericidal pine heartwood chips were mixed to a compound and injection molded into specimens, to create a plastic material with antimicrobial ingredients. An aim of this work was to preserve the bactericidal ingredients of pine heartwood chips (Pinus sylvestris) during compounding and injection molding into Polylactide wood compound specimens. Additionally, it was necessary to ensure the efficiency of the bactericidal ingredients especially at the surface of the specimens and the increase of the mechanical compound properties. Therefore, the specimens were tested with an antibacterial test method based on the ISO 22196:2011. Influences of different conditions such as temperature, chip size and chip content on the antimicrobial efficacy and mechanical properties were tested using a Design of Experiment. The specimens were tested for antibacterial activity, Charpy impact strength, surface hardness, Young’s modulus and yield strength. The results show significant dependencies between varied parameters and measured material properties.