Characterization of polyethylene-based multiphase systems containing zero- and two-dimensional nanoparticulate reinforcement materials by analytical electron and atomic force microscopy

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Multiphase polymer nanomaterials with reinforcements of different structural features have immense commercial applications. Characterization of the morphological features in these nanocomposites like filler dispersion, effect of filler and compatibilizer on polymer phase morphology, interaction of filler and compatibilizer, and so on is of significant importance as these shape the composite behavior and properties. To study these aspects, polyethylene (PE) nanocomposites generated with and without compatibilizer using two different types of fillers were comprehensively characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM) including analytical TEM (e.g. energy-dispersive x-ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS)). Differential scanning calorimetric analysis was performed in order to quantify thermotropical properties of the nanocomposites. The filler dispersion was poor in the absence of compatibilizer, whereas its addition enhanced the filler delamination owing to the positive interactions between the polar filler surface and polar component of the compatibilizer. The compatibilizer addition also decreased the melt enthalpy due to reduced crystallinity along with change in polymer phase morphology. The filler pullout was also observed even in the compatibilized samples leading to higher AFM height variation in these composites. The EELS and EDXS analysis was further useful in analyzing the type of filler phase as well as interactions between the filler and compatibilizer phases. The compatibilizer was also observed to concentrate near the interface with the filler as signal of oxygen atoms associated with compatibilizer chains did not enhance in matrix, but increased at organic–inorganic interface.