Silver/Hydrogen-Exchanged Zeolites Embedded in Modified Polyethylene Blends for Antibacterial Packaging with Prolonged Color Stability

Abstract

Antibacterial composite polymers are promising substrates for food packaging to reduce or inhibit the growth of foodborne pathogens. In this study, ion-exchangeable ions of zeolite were partially or wholly exchanged with silver (Ag + ) and ammonium ions and then subjected to heat treatment to generate hydrogen ions (AgH 1 Z) through the heat decomposition of ammonium ions. AgH 1 Z was incorporated into LDPE/LLDPE (70/30 w/w %) and their blends with ethylene vinyl alcohol copolymer (EVOH) and polyethylene-graf t-maleic anhydride (PE Ma ) to produce the corresponding antibacterial composite samples. The loading of the silver ion to the zeolite structure during the ion-exchange process and its efficiency were inspected by several analyses. The prepared composites possessing hydrogenexchanged zeolite (ΔE* of 0.11 for LL@AgH 1 Z) presented prolonged color stability relative to those without hydrogen (ΔE* of 13.87 for LL@AgZ). Interestingly, composite films have reliable optical properties (haze and transparency) compared to the corresponding neat polymer films. Scanning electron microscopy (SEM) micrographs illustrate that the addition of PE Ma to the LDPE/LLDPE matrix improves the AgH 1 Z particle dispersion, while EVOH induces a droplet-matrix morphology. The effect of AgH 1 Z and polymer blending on water vapor (WVTR) and the oxygen (OTR) transmission rate and mechanical behavior of composite samples were investigated. The silver ion release profile demonstrates a higher cumulative release amount for samples containing EVOH (0.069 mg) and PE Ma (0.044 mg) than that for the LL (0.039) sample, after 10 days of incubation in an acidic solution. The antibacterial activity results reveal remarkable inhibitory activity against Escherichia coli and Staphylococcus aureus bacteria for all composite samples. Furthermore, accomplished biocide performance shows a remarkable antibacterial response toward both bacteria with R values higher than 4, in the presence of EVOH and PE Ma polymers, which denotes their potentiality for advanced antibacterial food packaging.