Optimization of Gas Barrier Properties of Nanocomposites of HDPE/Nanoclay Using Response Surface Methodology

Polymeric fuel tanks have considerably lighter weight in comparison to metal tanks. However, a drastic reduction in evaporation of gasoline vapor from these fuel tanks is needed. The use of nanoparticles to produce polymeric nanocomposites can be an effective way to reduce the extent of permeability and enhance mechanical and processing properties. The planar nanoclay platelets have a substantial potential in enhancement of barrier properties of polymers. It should be noted that the type of compatibilizer plays a remarkable role in the dispersion state of nanoclay.

Nanocomposite samples were prepared using melt blending method in a twin screw extruder. In order to find the optimized formulation, the effects of nanoclay content, compatibilizer type, compatibilizer content and screw speed were assessed using response surface methodology (RSM). The optimization was performed based on the lowest gas permeability, favorable impact strength and melt flow index.

In general, the increment of nanoclay content led to improvement of the barrier properties, while compatibilizer content had an optimal level. The results of optimization revealed that the sample containing 10 wt% of maleic anhydride grafted polyethylene as compatibilizer and 6 wt% of organoclay (Cloisite 20A) possesses the optimum properties. Indeed, this sample showed an optimum balance between different properties and an exfoliated morphology for nanoclay platelets was obtained. On the other hand, although the oxidized polyethylene wax with high viscosity showed the lowest gas permeability, the impact strength and melt flow index were totally undesirable. Nanocomposite samples containing low viscosity oxidized polyethylene wax exhibited the highest gas permeability.