Role of nanoclay distribution on morphology and mechanical behavior of rubber-modified polyolefins

Polyolefin blends have attracted great attention for years because of their improved physical and mechanical properties; especially when micro/nanofillers are present in the compound. Previous investigations have proven that incorporation of small amounts of nanoclay can enhance physical and mechanical properties of the polymer. This research has focused on the role of clay distribution on morphology and mechanical properties of ternary nanocomposites containing a rubbery phase. High-density polyethylene/ethylene vinyl acetate/clay (HDPE/EVA/clay) is opted as a typical model for this purpose. EVA is selected to act as both compatibilizer, because of having polar vinyl groups, and rubber-modifier, because of its elastomeric properties, in this ternary blend. Nanocomposite preparation was performed via one- and two-step mixing routes to achieve two different desired morphologies. Tensile and Izod impact tests, and different microscopic techniques, were used to evaluate nanostructure and mechanical performance of blends. Results of the study proved two distinct morphologies forming as a result of different incorporated processing techniques. Mixing components simultaneously leaded to a structure in which, clay platelets are located at the HDPE/EVA interface, whereas in the two-step processing route, most of the clay platelets are encapsulated by the EVA second phase particles. According to the results of the current study, encapsulation of the nanofillers by the second rubbery phase harms mechanical properties of the blend and should be avoided. On the other hand, much better mechanical performance is obtained when the clay platelets are located at the matrix/rubber interface. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41993.