CHARACTERIZATION OF OCTAMETHYLSILSESQUIOXANE (CH3)8Si8O12 FILLERS IN POLYPROPYLENE MATRIX

The results of Raman microspectroscopy measurements of octamethylsilsesquioxane (om-POSS) (3-wt %) in polypropylene (PP) are presented and compared with theoretical spectra calculated by ab initio density functional theory (DFT) based methods. The internal structure of this dielectric composite at the micrometer level was obtained by Computerized X-ray microtomography (CXμT) which reveals how micron-scale filler particles are distributed in the matrix media. The X–ray powder diffraction (XPD) was used to determine the om-POSS inner crystallite size that is in a nanometer range. Transmission electron microscopy (TEM) images confirm that the composite contains both nano and micron sized particles. The multiscale analysis indicates that in the composite om-POSS crystalline nanoparticles having a size from tens to hundreds of nanometers tend to agglomerate together with preferred orientation to form elongated micron sized particles. Orientation of crystallites affects the relative intensity of various Raman peaks. Appearance of Raman images thus depends on the choice of the peak used in the analysis.