Thermal and Mechanical Properties of Antimicrobial Poly(lactic acid) Composites

Antimicrobial plastics containing benzalkonium chloride, 1,2-hexanediol/1,2-octanediol 1:1 mixture, and copper sulfide (CuS) powder biocides added alone or all together to a poly(lactic acid) composite containing 10 wt% of talc were manufactured by a twin-screw extruder and were injected into specimens for physical properties. In the both cases including the 1:1 mixture of 1,2-hexanediol and 1,2-octanediol or all three biocides, the heat resistance of the antibmicrobial poly(lactic acid) composite was slightly decreased. However, both benzalkonium chloride and copper sulfide showed its some improvement. Although the tensile strength didn't change by the addition of biocide, the tensile modulus was slightly decreased and the elongation at break was greatly decreased. Flexural strength also decreased with the addition of biocide, but flexural modulus slightly increased. Notched Izod impact strength showed a tendency to decrease with a slight difference depending on the biocide. The antibacterial performance was excellent in the cases containing benzalkonium chloride, but was poor in those containing the 1,2-alkanediol mixture or copper sulfide. The antifungal performance was the best when all three biocides were added, rather than those used alone. The sterilizing power of influenza A virus was excellent as 99.998% when all three were added. Mixing biocides showed a synergistic effect on the antimicrobial performance of poly(lactic acid) composites, but more efforts such as evaluating the effects of biocides on the human body are expected to contribute to securing the stability of poly(lactic acid) products.