Process parameters for modulating structure and properties of LDPE nanocomposites

Improvements of the poor oxygen-barrier properties of polyolefins is beneficial for extending their use in the food packaging field. To this aim, samples were prepared via direct melt intercalation of LDPE into lamellar silicates (organo-montmorillonite, D72T) in a co-rotating twin screw extruder using a compatibilizer consisting of maleic anhydride modified polyethylene (PE-g-MAH). The overall compositions of LDPE/PE-g-MAH/D72T nanocomposites were 90/9/1 and 70/27/3 weight %. The effect of feed and processing conditions upon the formation and properties of LDPE nanocomposites were deeply investigated. A combination of different analyses, X-ray diffraction and transmission electron microscopy for morphology assessment, thermal gravimetric analysis and differential scanning calorimetry as well as oxygen permeability measurements, tensile tests and on-line capillary rheological measurements, allowed to establish the level of clay dispersion, the improvement of thermal and mechanical properties, the preservation of polymer processability and the increase of barrier properties. Furthermore, a preferential orientation of the high aspect ratio nanofiller was evidenced and it will be discussed with reference to processing conditions.