Polymers breakdown voltage

Although the literature on electrodeposited electroactive and passivating polymers is vast, surprisingly few studies exist on the solid-state electrical properties of such films, with a focus on systems derived from phenolic monomers, - and apparently none exist on the use of such films as solid polymer electrolytes. To characterize the nature of ultrathin electrodeposited polymers as dielectrics and electrolytes, solid-state electrical measurements are made by electrodeposition of pofy(phenylene oxide) and related polymers onto planar ITO or Au substrates and then using a two-electrode configuration with a soft ohmic contact as the top electrode (see Figure 27). Both dc and ac measurements are taken to determine the electrical and ionic conductivities and the breakdown voltage of the film. 

The dielectric breakdown voltage or dielectric strength of polymers may be determined by ASTM-D149. The dielectric breakdown voltage is the maximum applied voltage that a polymer can withstand for 1 min divided by the thickness of the polymer. 

And it is also very important to give the material flame retardancy as well as high breakdown voltage. The mechanism of burning and combustion of silicone elastomers is very different from that of other synthetic polymers [1-4], Normally the synthetic polymers produce inflammable gases and water vapor in burning. Silicone elastomers also produce inflammable gases such as cyclo-siloxanes. However, silicone makes a three-dimensional structure by the oxidation reaction of siloxane side chain Furthermore, after the combustion it makes the ash silica. This makes silicones different from other polymers. 

Several tests are essential for the evaluation of plastics in electrical applications. These tests include dielectric constant (permittivity ASTM-D150-74), which is the ratio of the capacitance of the polymer compared to air, dielectric strength, and dielectric breakdown voltage (ASTM-D149-75). Dielectric breakdown voltage is... 

One of the concerns in commercial wire and cable application of crossllnked polyethylene technologies is the type and amounts of peroxide decomposition products (Figures 3 and 4) and their relationship to the polymer s dielectric strength performance capabilities. Peroxide decomposition products such as acetophenone have been shown to Increase the breakdown voltage limits of chemically crossllnked polyethylene materials (Figure 5). (2)... 

Ethylene oxide/propylene oxide triblock copolymers have been successfully used to template pore formation in ultra low-k films, and dielectric constants as low as 1.5 have been observed with polymer loading levels of 50 wt% (5). These films have good mechanical properties, a high breakdown voltage and a low moisture uptake. We have characterized the films with high-resolution solid-state proton NMR and found that the triblock copolymers form nm-sized core-shell structures with the propylene oxide block at the interface between the ethylene oxide block and the methyl silsesquioxane matrix (14). 

The dielectric strength of a polymer is a measure of its ability to withstand voltage without breakdown or the passage of considerable amounts of current. It is defined as the minimum voltage at or below which no breakdown occurs. Rather similarly, the breakdown voltage is the voltage above which actual failure occurs and the two items are often used interchangeably. 

Parylene films have excellent electrical properties with high volume and surface resistivitities whilst their dielectric constants and dissipation factors are quite low, although not as good as PTFE. The two main types of parylene are Parylene N and Parylene C. Parylene N is the unsubstituted polymer, whilst Parylene C is chlorine substituted. The best overall electrical properties are exhibited by Parylene N but Parylene C is superior with respect to D.C. dielectric breakdown voltage for films under 5 fxm in thickness. The principal electrical properties of parylenes are shown in Table 10.14. 

Figure 13.22 Tracking resistance and breakdown voltage of bulk samples of glass fiber-reinforced engineering plasties. TCP liquid crystal polymer UL Underwriters Laboratories.

Even for high voltages the breakdown voltage of a polymer electrolyte capacitor made by the deposition of PEE)OT PSS dispersions can be close to the anodization voltage of the dielectric (see Figure 10.12). Thus the... 

Comparison of breakdown voltage (BDV) of polymer tantalum capacitors having polymer cathodes made by chemical in situ polymerization (typical range) and by polymer dispersions (experimental data points). Tantalum anodes were anodized at 100 V. 

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