Dielectric Properties of LDPE/MgO Nanocomposites Micro-extruded from a Masterbatch

Abstract

Nanocomposites properties are strongly linked to their micro-structure and the quality of the nanoparticles distribution inside the matrix. A good distribution is reachable at the laboratory scale, as seen in the literature, but is somewhat more challenging to reach at the industrial scale with the usual cost, safety and environmental considerations. The most convenient way to produce thermoplastic based composites at the industrial level is to start from a polymer/filler masterbatch, with an adequate, but certainly not yet optimized, particles distribution, and to improve it by the means of further melt-mixing processing. This study is focused on the properties of LDPE/MgO nanocomposites compounded by the means of different thermo-mixing treatments and the purpose is to establish an appropriate melt-mixing procedure for material development with the desired dielectric properties. Low Density Polyethylene (LDPE) was used as a matrix and was reinforced by Magnesium Oxide (MgO) particles having an average size of 30 nm. The MgO nanoparticles were either treated or untreated with a silane coupling agent (3-Glycidyloxypropyl Trimethoxysilane). The primary samples were prepared in a melt-mixing chamber with a MgO content of 1%wt. Samples with untreated MgO and pure LDPE were also prepared in a similar way for comparison purposes. These pre-mixed samples were further treated by the means of thermo-mixing treatments provided by a conical co-rotating twin-screw extruder allowing optimizing the processing parameters. The sample dispersion was subsequently evaluated by Scanning Electron Microscopy (SEM). ACBD measurements were conducted and the resistance to space charge accumulation under DC fields was evaluated using a PEA setup.