Development and evaluation of antimicrobial LDPE/TiO2 nanocomposites for food packaging applications

Polymers used in food packaging should have unique properties, including anti-bacterial properties, good mechanical properties and permeability to air and water. To achieve these properties, some nanomaterials are incorporated into the polymeric matrix to be suitable for such a precise application. Thus, polymer nanocomposites emerged as one of the most important recent trends in the packaging materials industry. Here, titanium dioxide nanoparticles (TiO2-NPs) were synthesized by the sol-gel method and incorporated into pure low-density polyethylene (P-LDPE) at different concentrations (0, 2, 4, 8 wt %.). The prepared nanocomposites were characterized via a scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis. The size of TiO2-NPs is ranged from 13 to 47 nm. The crystallinity index of LDPE increased by the addition of TiO2-NPs from 0.32 to 0.55. Also, the thermal stability of LDPE improved by 67 degrees C. Studies of the mechanical properties, antibacterial activity and permeability measurements of nanocomposites films have demonstrated their potential for use in perishable food packaging. The results showed an increase in oxygen permeability from 55.25 cc/M-2 day for P-LDPE to 72.84 cc/M-2 day for LDPE-loaded with 8% TiO2. On the contrary, the impeded TiO2-NPs inside LDPE films reduced the water vapor transmission from 2.22 g/(m(2) day) to 0.92 g/(m(2) day). The tensile strength of P-LDPE increased from 16.7 MPa to 28.95 MPa for nanocomposite loaded with 8% TiO2. The ability of TiO2-NPs O-2 to generate the potentially reactive radical species induced the antibacterial activity of LDPE to Gram-negative and Gram-positive bacteria.