Effect of Pre–Strain on the Dielectric and Dynamic Mechanical Properties of HSIII Silicone


  1. Szabo, J.P.
  2. Underhill, R.S.
  3. Rawji, M.
  4. Keough, I.A.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN)
In this study, the mechanical and electrical properties of a silicone polymer were studied as a function of pre-strain in order to improve our understanding of dielectric breakdown phenomena in amorphous elastomeric materials. HSIII silicone (Dow Corning) films were prepared and studied by dynamic mechanical analysis, dielectric analysis, and dielectric breakdown experiments. It was found that the storage modulus increased significantly with uniaxial stretch, from 0.4 MPa in the unstretched state to 9.1 MPa at 250% uni-axial pre- strain. The mechanical loss factor was unaffected by pre-strain. The real and imaginary parts of the complex dielectric permittivity were also unaffected by the application of a biaxial pre-strain. For HSIII films with no pre-strain applied, the dielectric strength increased with decreasing thickness. The dielectric strength was also found to be strongly dependent on pre-strain, with a near doubling of dielectric strength with a 200% uniaxial pre-strain applied. A series of experiments carried out over a range of film thicknesses and at two pre-strain levels (0% and 200% uniaxial) demonstrated that both pre-strain and thickness independently affected the observed breakdown strength, and that pre-strain was the more important factor over the thickness range studied (25-430um).

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Report Number
DRDC-ATLANTIC-TM-2005-251 — Technical Memorandum
Date of publication
01 Jan 2006
Number of Pages

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