Polyethylene-clay nanocomposites: Processing-structure-property relationship

A brief overview of synthesis and characterization techniques of nanocomposites and the importance for considering clay layer orientation along with its dispersion in the nanocomposites is discussed. Although few earlier reports tried to qualitatively relate the clay orientation to the property enhancement, no quantitative study was present. The possible reason for this was the absence of a technique to quantitatively determine the 3D orientation of structures in a nanocomposite. In the present study a technique to determine the 3D orientation was developed. The effect of compatibilizer concentration on the orientation and dispersion of structures in polyethylene nanocomposite films was studied. It was shown that increase in concentration decreased the orientation of clay layer normals along the film thickness. The possible reason that could explain this behavior is discussed.; It was also of interest to study the effect of processing conditions on the orientation of structures in nanocomposite films and relate the change in orientation to film properties. Polyethylene nanocomposite films with varying thickness were extrusion cast using different draw down ratios. Decreasing thickness was observed to increase the clay basal plane orientation along the film machine direction which in turn was observed to increase the reinforcing ability of the clay layers in both pseudo-static and dynamic tensile property measurements. A model to theoretically predict the tensile modulus based on the degree of clay orientation is developed and its data compared to that obtained experimentally.; Bottles from 2 different nanocomposites varying in clay content were blow molded using varying processing conditions. It was observed that varying processing conditions did not have a significant effect on the orientation of the clay layers in the bottles. Effect of clay content on barrier properties, column crush strength and drop impact strength of nanocomposite bottles was also studied.