الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
With the rapid development of electric power insulation industry all over the
world, enhancement of the dielectric, thermal and mechanical properties of
insulating materials used in underground cables has become essential issue at present in order to design new insulation systems that can withstand higher operating temperatures, higher voltage levels and higher mechanical stresses. The Cross-linked Polyethylene (XLPE) insulation has been used as the main insulation in medium voltage. Today XLPE power cables are used in 600 kV AC and ± 320 kV DC transmission systems. This thesis aimed to improve the XLPE dielectric, thermal and mechanical properties XLPE using the concept of
nanotechnology. Chemically modified silicon dioxide (SiO2), titanium dioxide
(TiO2), and zinc oxide (ZnO) nanoparticles are used as fillers to enhance XLPE
characteristics. The different nanoparticles surfaces were activated using methane
sulfonic acid then the surface functionalization of nanoparticles was carried out
using amino silane coupling agent. This process reduced the agglomeration of
nanoparticles inside the polymer matrix and improved the distribution and
compatibility between nanoparticles and polymer matrix. Then, nonfunctionalized
and functionalized XLPE /SiO2, XLPE/TiO2 and XLPE/ZnO nanocomposites
samples, with different loadings of nanoparticles (0.5, 2, 3.5, and 5 wt.%), were
industrially synthesized and developed using the melt blending method which is the
master batch method in El-Sewedy Egy-tech. The morphology of nanoparticles
surface was examined using High-resolution transmission electron microscopy
(HR-TEM). The chemical structure and surface morphology of the prepared XLPE
nanocomposites samples were characterized by X-Ray diffraction (XRD) and field
emission scanning electron microscopy (FE-SEM). Then, the thermal, dielectric and
mechanical properties of the prepared specimens were studied. The thermal
analysis was studied using two techniques, Thermo-gravimetric analysis (TGA)
III
and Differential scanning calorimetry (DSC) analysis. The dielectric properties for
all nanocomposite samples, such as relative permittivity and dielectric loss were
measured in a frequency range from 1 Hz to 1 MHz and the AC breakdown voltage
was measured using standard sphere to sphere set up. The voltage and field
distributions in and around the samples were calculated using finite element
method (FEM). The mechanical properties for all nanocomposite samples were
investigated by performing tensile test to obtain the stress strain curve. from this
curve, the elongation and tensile strength were calculated.
The results showed that, all functionalized XLPE nanocomposite samples
exhibit better thermal, dielectric and mechanical properties compared to neat nd
nonfunctionalized XLPE nanoparticles. This can attributed to the low surface
energy of the functionalized nanoparticles that highly reduced the agglomeration of
nanoparticles inside the polymer and improved the compatibility with polymer
matrix.