Polystyrene dielectric properties

Polystyrene is a clear, amorphous polymer with a high stiffness and good dielectric properties. It is easily cross-linked by ionizing radiation. Often small amounts of divinyl benzene may enhance the degree of cross-linking.98... 

The dielectric properties of organic and polymeric materials are one of their more attractive properties. Table 4 gives the dielectric constants of PMMA and polystyrene which are typical polymer glasses. ... 

TABLE 4. Dielectric properties of PMMA and Polystyrene, where eAo is the dielectric constant at frequency /, and tand is a measure of the dielectric loss... 

The object of the present work was to Investigate the kinetics of the various photo-decomposltlons of polystyrene, in particular the early events in these reactions, using dielectric techniques, and to compare the results with those previously obtained. The results will, in addition, provide information regarding the effects of such photo-degradations on the dielectric properties of the polymer. 

Predictions concerning the low eflFectiveness of organics as adsorbents are well supported by experimental evidence in addition to their dielectric properties. Under conditions detailed earlier for our adsorption experiments, we saw no significant adsorption to polystyrene (8) or polyethylene reaction vessels (26). (See also Table IX and discussions concerning weak virus adsorption at the water-C2Cl3F3 interface and hydrophobic interactions.)... 

Let us mention that dielectrophoresis has also found wide application in manipulation and sorting of particles and biological cells. Together with standard electrophoresis, it is perhaps the most often used electrokinetic phenomenon with practical applications in mind. Even particle separation can be achieved by using microelectrode arrays [55]. Based on the dielectrophoresis phenomenon, a new technique has recently become available for particle or cell separation, namely the dielectrophoresis/gravitational field-flow fractionation (DEP/G-FFF). In DEP/ G-FFF, the relative positions and velocities of unequal particles or cells are controlled by the dielectric properties of the colloid and the frequency of the applied field. The method has been applied to model polystyrene beads, but, most interestingly, to suspensions of different biological cells [56]. 

Grosse, C. and Tirado, M.C., Measurement of the dielectric properties of polystyrene particles in electrolyte solutions, Mater. Res. Soc. Symp. Proc., 430, 287, 1996. 

While the dielectric properties of a polymer system clearly have engineering value, changes in dielectric behavior with composition yield fundamental information. The behavior of the dielectric loss factor, tan 5, for the polyurethane/polystyrene sequential IPN was investigated by Lipatov et al Employing a frequency of 300 Hz, they studied the effect of filler over the temperature range -130 to 20°C. In this temperature range, the polystyrene does not exhibit a maximum in tan S however, the polyurethane does, at a temperature just below 0°C. Figure 7.1 shows the effect of Aerosil content on the loss peak. For convenience, the maxima in tan 8 are collected in Table 7.1. 

Poly(phenylene oxides) have been used as one component in blends because of their excellent physio-chemical properties. The best known example is that based on poly(styrene) and poly-(2,6-dimethy-l, 4-phenylene oxide) (PPO), sold under the trade name Noryl by General Electric. The addition of PPO to polystyrene raises the glass transition, improves mechanical properties and improves resistance to flammability. Detailed studies on the dynamic mechanical and dielectric properties of these blends and several similar systems have been performed by MacKnight et al, among others. 

H.-W. Wang, K.-C. Chang, J.-M. Yeh, and S.-J. Liou, Synthesis and dielectric properties of polystyrene-clay nanocomposite materials. Journal of Applied Polymer Science, 91 (2004), 1368-73. 

Dielectric constants of polymers vary with frequency and can either increase or decrease depending upon molecular structure, and the presence of any additives or fillers. In order to be of use in electrical and electronic applications a plastic should have reasonably constant dielectric properties over a broad range of temperatures, frequencies and humidities. It is for these reasons that materials such as polyethylene, polystyrene and the fluorocarbons find such extensive usage as electrical insulators. 

Noryl n Poly(phenylene oxide) Trade name for a family of blends of polyphenylene oxide (PPO) with much less costly styrenic polymers. These blends have the processability, low water absorption, and good dielectric properties associated with polystyrene, while the PPO contributes heat resistance. Glass-reinforced grades are available. Manufactured by General Electric, U.S. 

Polystyrene aging in atmosphere typically takes the form of yellowing, loss of gloss, crack formation, and decline of mechanical and dielectric properties [83]. Yellowing prevents deeper penetration of radiation into the internal material. 

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