Compounding dissipation factor

Medium-permittivity ceramics are widely used as Class I dielectrics, and in order to be in this category they need to have low dissipation factors. This precludes the use of most ferroelectric compounds in their composition since ferroelectrics have high losses (tan S >0.003), particularly when subjected to high a.c. fields. 

Figures 1 and 2 show the bulk electrical properties of the two cured molding compounds. The dielectric constant and dissipation factor were determined before and after moisture exposure. For moisture exposure, the samples were placed in an autoclave at 100% relative humidity, 15 psig, and 250°F for 500 hours. Measurements...

Figure 2. Dissipation Factor - Molding Compound Initial and 500 Hours at 1 Atmosphere Steam...

Electrical properties of polyphenylene sulfide compounds are summarized in Table III. The dielectric constant of 3.1 is low in comparison with many other plastic materials. Similarly, the dissipation factor is very low. Dielectric strength ranges from about 500-600 volts per mil for the various compounds these values are quite high. Thus, both... 

Electrical properties. Fillers and additives significantly increase the porosity of polytetrafluoroethylene compounds. Electrical properties are affected by the void content as well as the filler characteristics. Dielectric strength drops while dielectric constant and dissipation factor rise. Metals, carbon, and graphite increase the thermal conductivity of PTFE compounds. Tables 3.19 and 3.20 present electrical properties of a few common compounds. 

Urea and uracil herbicides tend to be persistent in soils and may carry over from one season to the next (299). However, there is significant variation between compounds. Bromacil is debrominated under anaerobic conditions but does not undergo further transformation (423), linuron is degraded in a field soil and does not accumulate or cause carryover problems (424), and terbacd [5902-51-2] is slowly degraded in a Russian soil by microbial means (425). The half-hves for this breakdown range from 76 to 2,475 days and are affected by several factors including moisture and temperature. Finally, tebuthiuron apphed to rangeland has been shown to be phytotoxic after 615 days, and the estimated time for total dissipation of the herbicide is from 2.9 to 7.2 years (426). 

The top-down approach involves size reduction by the application of three main types of force — compression, impact and shear. In the case of colloids, the small entities produced are subsequently kinetically stabilized against coalescence with the assistance of ingredients such as emulsifiers and stabilizers (Dickinson, 2003a). In this approach the ultimate particle size is dependent on factors such as the number of passes through the device (microfluidization), the time of emulsification (ultrasonics), the energy dissipation rate (homogenization pressure or shear-rate), the type and pore size of any membranes, the concentrations of emulsifiers and stabilizers, the dispersed phase volume fraction, the charge on the particles, and so on. To date, the top-down approach is the one that has been mainly involved in commercial scale production of nanomaterials. For example, the approach has been used to produce submicron liposomes for the delivery of ferrous sulfate, ascorbic acid, and other poorly absorbed hydrophilic compounds (Vuillemard, 1991 ... 

Despite this better mode of strain dissipation in the Ct—Ct series the central C—C bond length in 2,3-dimethylbutane, the parent compound, is shorter than the extrapolated bond length of a hypothetical strainless parent Cq—Cq compound 79). This supports the proposal made before, that Q—Q bonds are intrinsically stronger than Cq—Cq bonds. If the difference in resonance stabilization of tertiary and secondary alkyl radicals was the dominating factor determining these bond strengths it should have no consequences for the bond lengths801. 

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