PhD Seminar - Shanshan Bian

Candidate

Shanshan Bian

Title

Thermal Properties of Nanodielectrics Developed by Electrospinning

Supervisor

Jayaram, Sheshakamal

Abstract

In the last few decades, polymeric materials with their unique non-wetting surface characteristics, light weight, excellent mechanical properties and their low cost, have surpassed the use of the conventional insulation materials. However, polymeric materials are incapable of withstanding the high heat that stems from surface arcing which comes about by the synergism of pollution, moisture and voltage. Surface arcing results in material loss due to heat ablation and/or electrical tracking of polymeric materials. In order to overcome these issues, inorganic fillers have been added to the base polymers to enhance their resistance to surface arcing while at the same time, their addition significantly reduces material cost, which instills their greater use. Micron sized fillers have been used to gain these desirable properties but due to limitations in material processability, they have reached their fill limit. Combined with the increased use of polymeric materials, limited by their processability using micron sized fillers, nano sized fillers have been viewed as replacements to micron sized fillers.

Nano sized fillers are characterized by large surface areas resulting in increased bond strengths that yield significant improvements in dielectric properties at fill levels well below that of micron sized fillers. However, the main problem of using nano sized fillers is their characteristic property of agglomeration that comes about mainly due to their physical size and the forces between the particles. Conventional mechanical mixing of nanofillers, do not adequately separate the nano sized particles therefore their implementation is not completely effective. Chemical dispersion techniques, for example the use of surfactants, are normally very complicated and elaborate to use. In our study electrospinning is demonstrated for dispersing nanofillers in polymeric materials in our study.

This unique technique is able to successfully achieve polymeric nanodielectrics with improved properties. The improvements in electrospun nanodielectrics arise from the uniform distribution of filler. Scanning electron microscopy (SEM) images and energy dispersive X-ray analysis (EDAX) clearly show that electrospun nanodielectrics have better filler distribution than nanodielectrics produced by conventional mechanical mixing. The tracking and erosion resistance, thermal conductivity, heat stability and heat ablation of electrospun nanodielectrics are compared to conventional nanodielectrics for silicone rubber .All the experimental studies confirm that electrospun nanodielectrics have better thermal properties than the conventional composites which are attributable to the improved distribution of nanofillers by electrospinning process.