Effect of Clay Types on the Properties of Silane Compatibilzied Metallocene Polyethylene/Clay Nanocomposites
The interaction between the intercalant within clay and the compatibilizer is essential to the properties of nanocomposites, and the compatibilizer properties are often neglected. In this work, we have deliberately used a low crystallinity polyolefin elastomer as a compatibilizer to investigate if the inferior mechanical properties of the compatibilizer compared with those of the matrix would counteract the effects of high dispersion of clay in the mPE/clay systems. Melt-mixed mPE (metallocene polyethylene)/clay nanocomposites were thus prepared using a low-crystallinity polyolefin elastomer (mPE-g-silane) as a compatibilizer under two different types of commercial clay (Cloisite 20A and 30B) with different organic affinities to mPE-g-silane, to investigate both intercalant and compatibilizer effects. According to X-ray diffraction and transmission electron microscopy analyses, all 20A-filled nanocomposites showed fairly well-dispersed clay within the mPE matrix in comparison with 30B-filled cases due to a larger d-spacing of 20A for easier access of the compatibilizer, even though a higher affinity between 30B and the compatibilizer was expected. Measurable gel content was observed for 20A-filled systems, but not for 30B-filled systems. Tensile properties and tear strength of 20A-filled samples were higher than those of 30B-filled samples, again due to the high dispersion effect in 20A-filled samples. Thus, the affinity of 20A clay with silane agent was quite essential for these compatibilized mPE/clay systems, despite of the weak mechanical properties of the compatibilizer. Clearly, a subtle balance of the interfacial interaction, interface properties and clay dispersion is essential to attain the good mechanical properties of mPE/clay nanocomposites.