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Novel analytical techniques for the assessment of degradation of silicone elastomers in high voltage applications

By Robert D. Sovar


Over the last 20 years "composite" insulators have been increasingly used in high voltage applications as an alternative traditional materials. More recently, polydimethylsiloxane (PDMS) have been used as weather sheds on these composite insulators. The main attraction with PDMS is that the surface hydrophobicity can be recovered following pollution or surface discharges. Among the possible mechanisms for recovery the most likely is the migration of low molecular weight silicone oil (LMWS) from the bulk to the surface encapsulating pollutant particles. Although it is widely recognised that the migration of LMWS is the cause of this recovery of hydrophobicity, the mechanism of what actually occurs is not well understood. It is also not known for how long this process will continue. The main objective of this study program was to gain improved understanding of the surface hydrophobic recovery process that is unique to polydimethlysiloxane high-voltage insulators. Fundamental knowledge of this mechanism has been increased through the development of the Contact Angle DRIFT Electrostatic Deposition (CADED) novel analytical technique. This technique enabled study of the degradation of silicone elastomers subjected to high voltage environments by closely following LMWS migration from the bulk material to the surface and linking it to the contact angle measurements. The migration rate data showed that the aged material recovered faster that the virgin material. Differences in the rate and maximum surface levels of silicone were seen between materials from different manufacturers. This has significant implications for the life-time of these materials A model system has been developed to examine LMWS diffusion through the bulk material and into the interface of surface and pollutant. This was achieved by examining theoretical and empirically derived equations and using existing experimental data to better understand the mechanism of recovery. This diffusion was Fickian in the initial stages of recovery. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to substantiate the degree of degradation in in-field silicone insulators by quantifying the levels of the major degradation products: silica and silica-like material and alumina

Topics: Composite insulators, polydimethylsiloxane (PDMS), low molecular weight silicone oil (LMWS), polydimethlysiloxane high-voltage insulators, Contact Angle DRIFT Electrostatic Deposition (CADED), hydrophobicity, Silicone Elastomers, high voltage, applications
Publisher: Queensland University of Technology
Year: 2005
OAI identifier:

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  3. (2000). Are Composite Insulators Any Good?
  4. (2002). Assessment of the Diffusion of Low Molecular Weight Silicone Fluids on Polluted HV Silicone Elastomers by Diffuse Reflectance FT-IR, Unpublished Data.
  5. (2001). Chapter 2 – From Sand to Silicones: An Overview of the Chemistry of Silicones, in Silicones and Silicone-Modified Materials,
  6. (1998). Characterizing Synthetic Polymers by MALDI MS”, Anal.Chem,
  7. (1995). Chemistry and Technology of Silicones;
  8. (1991). Comparison of different methods for contact angle measurement”,
  9. (1998). Condition Assessment of Composite Insulator, PhD Thesis,
  10. (1991). Diffusion in and through polymers: principles and applications.,
  11. (1968). Diffusion in Polymers,
  12. (1999). Diffusion of Low Molecular Weight Siloxane from Bulk to Surface”,
  13. (1999). Drop Corona Effects on FullScale 500kV Non-Ceramic Insulators.
  14. (2001). Effects of RF plasma on the degradation of silicone oils”; 38 th IUPAC Congress,
  15. (1978). Fourier Transform Infrared Spectroscopy,
  16. (1985). Further Developments in the Methodology of Surface Analysis by FT-IR: Quantitative Aspects of Diffuse Reflectance Methods”,
  17. (2003). G.L.;”Comparative studies of poly(dimethylsiloxanes) using automated GPC-MALDI-TOF MS and on-line GPC-ESI-TOF MS”,
  18. (1992). High Resolution XPS of Organic Polymers,
  19. (1993). History and Bibliography of Polymeric Insulators for Outdoor Applications”,
  20. (2000). in “Practical Sampling Techniques for Infrared Analysis”,
  21. (1999). LMW Components in Silicone Rubbers and Epoxy Resins”,
  22. (1996). Non-invasive Raman spectroscopic identification of intraocular lens material in the living human eye.”,
  23. (1994). Oxidative Damage and Recovery of Silicone Rubber Surfaces.
  24. (1990). Physical Chemistry of Surfaces,
  25. (1999). Physical models of diffusion for polymer solutions, gels and solids”,
  26. (1988). Quantitative Analysis by DRIFT and Linear Stepwise Multiple Regression Analysis I”,
  27. (1999). Real-time FTIR-ATR spectroscopy to study the kinetics of ultrafast photopolymerization reactions induced by monochromatic UV light”,
  28. Silicon for the Chemical Industry
  29. (1990). Silicon-Based Polymer Science, A Comprehensive Resource”
  30. (2001). Studies on Plasma Polymerisation of Hexamethyldisiloxane in
  31. (1980). Surface dielectric behaviour of polymeric insulation under HV outdoor conditions,”
  32. (1990). The Loss and Recovery of Hydrophobicity of RTV Silicone Rubber Insulator Coatings”,
  33. (2003). Tthe dependence of the rate of crosslinking in poly(dimethylsiloxane) on the thickness of coatings”,
  34. (2001). Using linear and branched polysilanes for the photoinitiated polymerisation of a commercial siliconeacrylate resin. A real time FTIR study”,

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