Oxygen permeability analysis of microfibril reinforced composites from PE/PET blends

Polymers, their blends and composites are the most widely used types of barrier materials in the world today. This study uses an experimental design technique to investigate the oxygen permeability of a new type of microfibril reinforced polymer-polymer composite (MFC). It is based on blends of polyethylene (PE) and poly(ethylene terephthalate) (PET) in the ratio of 70/30 (wt%) to create composites without sophisticated processing techniques or expensive coatings, but with oxygen barrier properties superior to those of neat PE. Microfibril reinforced films of 150-200 mu m thickness were produced using a variety of manufacturing conditions, cooling conditions and fibre orientations. All films have been shown to possess superior oxygen barrier properties compared to the plain PE films, with the best allowing just over one quarter of the oxygen permeation that was observed through standard PE. Scanning electron microscopy of these films revealed significant differences in microstructure and reinforcement morphology of the films made using different manufacturing parameters. It has been noted that the films allowed to cool slowly, while they remained under pressure in the press decrease permeability significantly, in part due to increases in crystallinity. Statistical analysis has evaluated the impact of each manufacturing parameter on permeability. Generally, manufacturing and cooling conditions appear to have greater influence on barrier properties than the fibril orientation. Many of the MFC films also had tensile strength and modulus well in excess of that of neat PE, with the best film having triple the modulus and nearly double the strength of the unreinforced matrix polymer. (c) 2008 Published by Elsevier Ltd.