Preparation and antimicrobial assessment of zinc-montmorillonite intercalates based HDPE nanocomposites: A cost-effective and safe bioactive plastic

Zinc-montmorillonite intercalates based high density polyethylene (HDPE) nanocomposites were prepared by melt compounding route as an affordable and non-toxic substitute for silver based antimicrobial plastics, which are costly and sometimes toxic to human tissues. Zn is an essential trace element important for growth in humans and shows acceptable antimicrobial behavior, but its antimicrobial attribute has been largely unutilized. Zn ion exchanged montmorillonite (Zn-MMT) and ZnO nano-particles (NPs) decorated MMT (ZnO-MMT) were synthesized in lab using a combination of simple ion exchange and reduction reactions. The synthesized intercalates were melt mixed in HDPE at different concentrations to obtain HDPE/Zn-MMT and HDPE/ZnO-MMT nanocomposites with uniform dispersion of incorporated nano-additive. For comparison, HDPE/ZnO nanocomposite without MMT was also synthesized. A mixture of intercalated and exfoliated microstructure at lower loadings and intercalated morphology at higher loadings was confirmed by both TEM and WAXD studies in the nanocomposites. The antibacterial properties and antifungal properties were evaluated against gram-negative E. coli, gram-positive S. aureus and black mold fungi A. niger. Remarkable reduction in bacterial colonies and significant zone of inhibition was obtained for the Zn-montmorillonite intercalates and HDPE nano composites at 5 wt% of loading. The nanocomposites demonstrated no lysis of human RBC cells in hemolytic assay and no effect in human dermal fibroblast cell proliferation in MIT assay asserting its non-toxic nature, in contrast with HDPE/ZnO nanocomposite which showed mild cytotoxic behavior. (C) 2018 Published by Elsevier Ltd.