Dielectric-loss tangent

The observation of these dielectric relaxation processes arising from carbonyl features, has also been reported by Tibbit and co-workers in plasma polytetra-fluoroethylene as well as other plama polymers. In measuring the dielectric loss tangents over a frequency range of 10 -10 Hz at temperatures of — 150 to 100 °C, they have demonstrated that the dielectric loss curves of plasma polymers derived from hydrocarbon and fluorocarbon monomers are very similar, but bear no resemblence to their conventionally polymerized counterparts. 

F ure 6.37 Mechanical and dielectric loss tangents for poly (chlorotrillnoroethylene). Reprinted, by permission, from F. Rodrignez, Principles of Polymer Systems, 2nd ed., p. 271. Copyright 1982 by Hemisphere Publishing Corporation. 

Plasticizers include tricresyl phosphate and trixylyl phosphate. Foaming agents can be added in the case of using the polymers for wires, which require low dielectric constant and low dielectric loss tangent, such as communication cables, coaxial cables for computers and high-frequency cables. 

The adhesives are suitable for use in flip chip bonding of semiconductor parts. They exhibit good shelf stability, productivity, strength properties and heat resistance. The electrical properties, such as dielectric constant and dielectric loss tangent are highly satisfactory. 

The dielectric constant is generally different in the crystalline and amorphous phases. In this case, Xc in Eq. (95) does not mean the volume fraction of the crystalline phase itself. Furthermore, the amorphous phase exhibits dielectric relaxation in the region where the mechanical relaxation occurs. Considering this effect, Xc should be taken as a complex quantity with a negative imaginary part. However, the inequality (100) is valid in so far as the dielectric loss tangent is smaller than the mechanical one. The inequality (101) holds more generally because the effect of dielectric relaxation enhances the positive value of d"jd. ... 

Fig. 75 Dielectric loss tangent vs temperature for 11 at different frequencies (from [57])...

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. 

Dielectric loss tangent The difference between 90° and the dielectric phase angle for a material. 

Dielectric Measurements. The dielectric properties of Resin 5208 were followed for isothermal cures of 110, 125, 137, 148, and 162"C at several frequencies. Figure 7 shows the time dependence of the dielectric loss tangent for the combination of the PTFE... 

An analysis of the dielectric data similar to that for the dynamic mechanical data was undertaken. The natural logarithm of the time to peak maximum vs. 1/T was plotted for the two peak maxima observed in the dielectric loss tangent as shown in Figure 11. The activation energies derived from linear least squares fit of the data in these plots are listed in Table II. 

The electical properties of amorphous poly-DSP are characterized by a small temperature dependence of the dielectric constant measured between room temperature and 100 °C. The dielectric loss tangent is small and, in addition, the dc conductivity is extremely low. 

The extent to which a material is heated when subjected to microwave radiation depends on two parameters the dielectric constant e and the dielectric loss factor e". The dielectric constant describes the ease with which a material is polarized by an electric field, while fhe loss factor measures fhe efficiency wifh which the electromagnetic radiation is converted into heat. The ratio of these properties gives the dielectric loss tangent or dissipation factor ... 

Figure 19. Dielectric loss tangent as a function of temperature for plasma-pdymerized ethylene at four frequencies (76). (O) lO Hz, (A) lO Hz, ( ) 10 Hz,...

The majority of studies on the structure and properties of Nafion membranes are very often performed on the dry or humidified samples while many important applications of these materials are in the "wet form. The knowledge pertaining to the interaction between the solvents and the polymer by the use of the solubility parameter should facilitate the understanding of the structure-property-performance relationship. Investigations of ionic transport (13), spectroscopic properties (14) and dielectric loss tangent (12) of the membrane in light of the solubility parameter could prove to be an interesting and perhaps profitable line of inquiry. 

Dielectric Loss Tangent - See Dielectric Dissipation Factor. 

Since temperature usually tends to increase the conductivity of a ceramic exponentially (Chap. 7), its effect on dielectric loss can be substantial. This is demonstrated in Fig. 14.14a, where the loss tangent is plotted as a function of temperature for different glasses that have varying resistivities. In all cases, the increased mobility of the cations results in an increase in the dielectric loss tangent. The effect of impurities, inasmuch as they increase the conductivity of a ceramic, can also result in large increases in the dielectric loss. This... 

Table 5.1 The dielectric loss/tangent delta maximum...

Gate dielectric loss tangent d degrees X Optional... 

Polymer Dieleetrie permittivity e, eonventional polymer Dielectric permittivity e, plasma polymer Dielectric loss tangent tan S, eonventional polymer Dielectric loss tangent tan S, plasma polymer... 

---