Surface Modification of Fumed Silica by Plasma Polymerization of Acetylene for PP/POE Blends Dielectric Nanocomposites

Abstract

Novel nanocomposites for dielectric applications-based polypropylene/poly(ethylene-co-octene) (PP/POE) blends filled with nano silica are developed in the framework of the European ‘GRIDABLE’ project. A tailor-made low-pressure-plasma reactor was applied in this study for an organic surface modification of silica. Acetylene gas was used as the monomer for plasma polymerization in order to deposit a hydrocarbon layer onto the silica surface. The aim of this modification is to increase the compatibility between silica and the PP/POE blends matrix in order to improve the dispersion of the filler in the polymer matrix and to suppress the space charge accumulation by altering the charge trapping properties of these silica/PP/POE blends composites. The conditions for the deposition of the acetylene plasma-polymer onto the silica surface were optimized by analyzing the modification in terms of weight loss by thermogravimetry (TGA). X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray fluorescence spectroscopy (EDX) measurements confirmed the presence of hydrocarbon compounds on the silica surface after plasma modification. The acetylene plasma modified silica with the highest deposition level was selected to be incorporated into the PP/POE blends matrix. X-ray diffraction (XRD) showed that there is no new crystal phase formation in the PP/POE blends nanocomposites after addition of the acetylene plasma modified silica. Differential scanning calorimetry results (DSC) show two melting peaks and two crystallization peaks of the PP/POE blends nanocomposites corresponding to the PP and POE domains. The improved dispersion of the silica after acetylene plasma modification in the PP/POE blends matrix was shown by means of SEM–EDX mapping. Thermally stimulated depolarization current (TSDC) measurements confirm that addition of the acetylene plasma modified silica affects the charge trapping density and decreases the amount of injected charges into PP/POE blends nanocomposites. This work shows that acetylene plasma modification of the silica surface is a promising route to tune charge trapping properties of PP/POE blend-based nanocomposites.

Silica Surface-Modification for Tailoring the Charge Trapping Properties of PP/POE Based Dielectric Nanocomposites for HVDC Cable Application

“…It is obvious that there are two melting and crystallization peaks corresponding to the two polymer phases. In accordance with the previous results [30], the first peak at the lower temperature originates from the POE phase, in which the crystalline PE domains melt (or crystallize), while the second peak at higher temperature comes from the PP phase.…”

“…The results are shown in Fig.13. Three different crystal phases (α and β crystals of the PP phase and orthorhombic crystals from the PE phase) are detected, as have been reported in previous work [30]. It is important to notice that no obvious increase of the β crystal content in the silica filled PP/POE composites was recorded (both untreated and treated silicas).…”

Rheological study of EPDM/silicone rubber blends phase inversion and characterization of resultant mechanical and thermal properties

“…In the ES3 compositions onwards, we note the appearance of a defined SR melting area around −45 C, which has a peak shifted to higher temperatures and rising area with increasing SR concentration. 33,34 This peak shift, as well as the general characteristic of the curves obtained, corroborates with results found in the literature that indicate a certain structural interaction between EPDM and SR, also pointing out that there may be differences arising from the measurement method used and the specific grades of each polymer, which have several variations and specifications available on the market. 7,8 Regarding the thermal conductivity of the blends, it is noted that there is a drop in the conductivity values in a linear trend as the SR concentration increases (Figure 7).…”

Preparation, Characterization and Adsorption into Aqueous Solutions of Polyethyleneimine-Coated Silica Nanoparticles

“…Strong O 1s (533.2 eV) and Si 2p (103.5 eV) peaks are characteristic of silica nanoparticles. A Si and a few O peaks between the 25 and 104 eV energy interval are considered as the fingerprints of silica nanoparticles (32). Moreover, C 1s (283.8 eV) was observed due to hydrocarbon contamination residues that interacted during sample preparation for XPS.…”