One commonly used strategy to enhance polymers specific properties such
as the resistance to partial discharges erosion is the incorporation into the
polymeric matrix of inorganic micro or nanoparticles. This study focused on the
dielectric properties of Low-Density Polyethylene (LDPE) filled with nano-sized
Magnesium Oxide (MgO) particles compounded by thermo-mechanical process and one
of the purposes was to establish appropriate processing parameters in order to
reach the desired dielectric properties. LDPE was used as a matrix and was reinforced
by MgO particles having a nominal average size of 30 nm. The MgO nanoparticles
were treated with a silane coupling agent (3-Glycidyloxypropyl
Trimethoxysilane). The samples were initially prepared in a melt-mixing chamber
with a MgO content of 1% wt. These pre-mixed samples were further treated by
the means of thermo-mechanical mixing in a conical co-rotating twin-screw
extruder in order to improve the dispersion and distribution of the MgO
particles. In this report, both lifetime under a PD activity and AC dielectric
strength of pure and nano-filled LDPE samples have been
measured and compared. Nano-filled LDPE samples were found to exhibit an
improve lifetime, without any detrimental impact on their short-term dielectric
strength. This suggests that nano-filled LDPE may be for electric applications
for which the dielectric materials may be exposed to partial discharge
activities. This is significant result for the use of MgO-reinforced PE as an
insulating material for HV cables since the resistance to PD is closely related
to treeing resistance which is the main electrical degradation mechanism that
leads to failure for shielded extruded power cables.
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