Dielectric strength of silicone

Table VI. Effect of Chemical Composition on the Dielectric Strength of Silicone Fluids of the Form (CH3)3SiO RCH3SiO)xSi(CH )3...

Dielectric spectroscopy, in silicone network characterization, 22 569 Dielectric stiffness, 11 93 Dielectric strength, of plastics, 19 587 of thermoplastics, 10 176... 

Silicone laminates are useful from cryogenic temperatures to about 260°C. The dielectric properties of silicones are particularly useful. Both dissipation factor and dielectric constant are low at room temperature and remain relatively constant up to 150°C. Because of the presence of the silicon atom, silicone laminates have good arc- and track resistance. The physical properties of silicones are not greatly influenced by aging, but compared with laminates that are based on other resins, the flexural and tensile strengths of silicones are not unusually high. Silicone laminates are used in electronics, heaters, rocket components, slot wedges, ablation shields, coil forms, and terminal board. 

The Johnsonfigure of merit, based on saturated carrier velocity and dielectric strength (product of power x frequency squared x impedance), predicts the suitability of a material for high power applications. It is normalized with the value of one given to silicon. As shown in Table 13.2 below, diamond is clearly the preferred material on this basis. 

Polysiloxanes, also called silicones, are characterized by combinations of chemical, mechanical, and electrical properties which taken together are not common to any other commercially available class of polymers. They exhibit relatively high thermal and oxidative stability, low power loss, high dielectric strength, and unique rheological properties, and are relatively inert to most of the ionic reagents. Almost all of the commercially utilized siloxanes are based on polydimethylsiloxane with trimethylsiloxy end groups. They have the widest use... 

Of considerable interest is the use of silicone rubbers for insulation in electrotechnical equipment. This is accounted for by superior heat resistance of elastomers and their good dielectric properties. E.g., the dielectric permeability of polyorganosiloxane elastomers at 500 V and 60 Hz is 3.5-5.5, their electric strength at 60 Hz is 15-20 KV/mm, and the dielectric loss tangent, which characterises the losses of electric energy in insulation, at 500 V and 60 Hz amounts only to 0.001. It is very important that these characteristics are preserved in a much wider temperature range than in the case of natural and synthetic organic elastomers. 

The industrial ceramics produced by conventional sintering of 8-phase Si3N4 powders synthesized by SHS (Petrovskii et al, 1981) can be used as high-temperature articles with attractive dielectric properties (tan6=4.4 10 at/= 10 Hz, and dielectric strength, Ea=9.2 kV/mm). Also, silicon nitride powders with a relatively high a-phase content ( 80%) have been used for the production of advanced structural ceramics with good mechanical properties ([Pg.109]

The most stable, adhesive and hydrophobic silicalite-1 films can be obtained by in situ crystallization on the silicon substrate, followed by calcination to remove the organic template.[105] Their elastic modulus reaches 30-40 GPa, but the dielectric constant was measured to be 2.7-3.3. These findings suggest an inverse relationship between the mechanical strength of the films and the lowest achievable dielectric constant. 

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