High dielectric constant polymer composites

Rao, Y., Ogitani, S., Kohl, P, and Wong, C.P., High dielectric constant polymer-ceramic composite for embedded capacitor application, in Proceedings of the International Symposium on Advanced Packing Materials Processes, Properties, and Interfaces, IEEE, Piscataway, NJ, 2000. 

Nearly every polymeric system absorbs some moisture under normal atmospheric conditions from the air. This can be a difficult to detect, very small amount as for polyethylene or a few percent as measured for nylons. The sensitivity for moisture increases if a polymer is used in a composite system i.e. as a polymeric matrix with filler particles or fibres dispersed in it. Hater absorption can occur then into the interfacial regions of filler/fibre and matrix [19]. Certain polymeric systems, like coatings and cable insulation, are for longer or shorter periods immersed in water during application. After water absorption, the dielectric constant of polymers will increase due to the relative high dielectric constant of water (80). The dielectric losses will also increase while the volume resistivity decreases due to absorbed moisture. Thus, the water sensitivity of a polymer is an important product parameter in connection with the polymer s electrical properties. The mechanical properties of polymers are like the electrical properties influenced by absorption of moisture. The water sensitivity of a polymer is therefore in Chapter 7 indicated as one of the key-parameters of a polymeric system. 

The ion conductivity of the three PEO/PMMA blend compositions, 25/75, 50/50, and 75/25 studied by us increases with ascending LiClO content due to increasing number of free mobile ions as shown in Figure 28. In addition, blend composition with 75 wt% PEO doped with 0 to 12 wt% LiClO displays comparatively higher a values in the order of 10 S cm than the other two blends. Nevertheless, Tan and Johan, (2011) studied the ion conductivity of PEO/PMMA blend polymer electrolyte found that the composition 20 wt% PEO and 80 wt% PMMA is the most miscible proportion for the blend. Figure 28 depicts that the PEO/PMMA 20/80 blend achieves a maximum ion conductivity of 7 x 10 S cm at 10 wt% LiClO, further enhancement in conductivity can be achieved by the addition of a low molecular weight, low viscosity, and high dielectric constant plasticizer, EC. The incorporation of EC facilitates the dissociation of the... 

Arbatti M, Shan X, Cheng ZY. Ceramic-polymer composites with high dielectric constant. Adv Mater May 2007 19(10) 1369-72. 

High Dielectric Constant (Microwave Frequencies) Polymer Composites... 

Surface tension of a polymer solution can be controlled by judicious selection of the solvent. The very different surface tensions of poly(vinyl chloride) (PVC) solution at constant concentration in various DMF/THF mixtures are shown in Fig. 4.5a. Note, however, that on changing the solvent composition the viscosity also increases threefold at constant polymer concentration (Lee, K. H., et al. 2002). DMF is a polar solvent with a high dielectric constant (36.7 at 25°C) and high boding point (153°C), whereas THF has a low dielectric constant (7.6 at 25°C) as well as a low boiling point (65°C). 

Carbon black nanoparticle-reinforced polyisoprene applied in electric heating elements and resistors as thermodynamically inactive materials for a high dielectric constant (>1000) has been studied. The dissipation factor (tanS) of this carbon black nanocomposite was high (Xu and Wong, 2005). However, improving the dispersion of the nanoparticles in polymer lowers the percolation threshold of composites (Raza et al., 2012 Sumfleth et al., 2011). The electrical conductivity of rubbery epoxy/carbon black nanocomposites at 8 wt% filler loading was 2 x 10 S/m, which matched the criterion of electrical conductivity for electrostatic applications (10 S/m) (Ali Raza et al., 2012 Knite et al., 2004 Sasha Stankovich et al., 2006). 

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