Rheological, structural, ultraviolet protection and oxygen barrier properties of linear low- density polyethylene films reinforced with zinc oxide (ZnO) nanoparticles

Linear low-density polyethylene (LLDPE) and zinc oxide (0-10%, w/w) nanocomposite (NC) films were produced through melt-mixing extrusion process. Both LLDPE and LLDPE/ZnO NC exhibited predominating liquid-like property in the lower frequency range, however, a distinct gel point was detected at higher frequency. At 10% loading of ZnO to LLDPE followed the time-temperature-superposition (TTS) principle adequately in the selected temperature range (140-170 degrees C). Tensile strength (TS) of the NC increased whereas the elongation at break (EAB) decreased with increasing loading concentration of ZnO. NC films showed lower transparency, b*-values (yellowness), and Delta E*-values (total color difference) than the control LLDPE film. Incorporation of ZnO improved the ultraviolet (UV) barrier properties whereas the oxygen transmission rate decreased significantly from about 11,000 to 8000 cm(3)/(m(2) 24 h). X-ray diffraction (XRD) analysis confirmed the crystalline structure of the NC films, and an improvement in thermal stability was detected through thermogravimetric analysis. Scanning electron microscopy (SEM) exhibited well dispersion of nanoparticles in the NC matrix with a coarse film surface. Thus, LLDPE/ZnO nanocomposite films could be used as a food packaging material to prevent oxygen and UV induced lipid oxidation in food materials.