Tensile, barrier, and degradation properties of low density polyethylene/epoxidized natural rubber nanocomposite films

Abstract

The demand for the development of high-performance packaging films and the equally growing environmental awareness have called for intensive research in the field of eco-friendly films with good mechanical and barrier properties. The present study investigates the use of epoxidized natural rubber (ENR) and organo modified montmorillonite (OMMT) in the development of low density polyethylene (LDPE) nanocomposites films. The films were successfully prepared by first melt blending at 190 °C in a twin-screw extruder and then blown via single screw machine. Linear low density polyethylene-grafted-maleic anhydride (LLDPE-g-MA), was used as compatibilizer to obtain better dispersion of nanoclay in the system. The nanocomposite films were prepared at different amounts of rubber from 2.5-10 wt%. The obtained nanocomposites were analyzed for tensile, thermal, morphology, gas permeability and degradation properties. The study of tensile properties of films was done via Lloyd 2.5 kN according to ASTM D882 in machine direction. Thermal analysis was carried out via differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). Atomic force microscope (AFM) was used to probe the morphology of phases, and X-ray diffraction (XRD) was applied to examine the interlayer distance of OMMT. Chemical characterization and interaction between materials were studied by Fourier transform infrared spectroscopy (FTIR). The barrier property of films was determined by constant pressure/variable volume type permeation cell. Degradation and biodegradation were studied via Q-SUN Xenon test chamber and soil burial test, respectively. The study has shown the presence of OMMT enhanced the tensile modulus and barrier property of LDPE film by 46% and 80%, respectively. In addition, incorporation of ENR improved the Young‘s modulus and barrier properties of compatibilized nanocomposite films. Improvement in the degradation onset temperature (T- 10%) of nanocomposite films was observed with addition of 6wt% OMMT and ENR contents. The intercalation of OMMT regarding addition of LLDPE-g-MA into nanocomposites was confirmed by XRD. FTIR analysis has shown a formation of (C-O) ester bond; the driving force for intercalation between MA group of LLDPE-g-MA and epoxy group of ENR. Significant degradation took place through addition of OMMT and ENR as samples were highly fragile and broken. Biodegradation of films increased through addition of ENR. The most significant finding from this research is the development of eco-friendly nanocomposite film formulation with enhanced barrier properties. Based on tensile modulus, barrier and biodegradation properties, compatibilized nanocomposites film containing 7.5 wt% ENR (LDPE/OMMT/LLDPE-g-MA/ENR7.5) was the optimum formulation. The unique combination of tensile modulus, barrier and biodegradation properties for nanocomposite films has shown that this nanocomposite is a potential candidate for a variety of food packaging applications.