Dielectric properties of isotactic polypropylene nitrile rubber blends: Effects of blend ratio, filler addition, and dynamic vulcanization

The dielectric properties of isotactic polypropylene/acrylonitrile-butadiene rubber blends have been investigated as a function of frequency with special reference to the effect of blend ratio. The dielectric properties measured were volume resistivity, dielectric constant (epsilon'), dissipation factor (tan delta), and loss factor (epsilon "). At high frequencies, a transition in relaxation behavior was observed whereby the dielectric constant of the blends decreased with frequency, whereas the loss tangent and loss factor increased on reaching a maximum. The variation of the dielectric properties with blend composition was correlated with blend morphology, and relationships were established with reference to blend composition. Experimental epsilon' values were compared with theoretical predictions. The effect of the addition of fillers on the dielectric properties was also investigated for different fillers and filler loadings. It was found that silica filler increases the dissipation factor, whereas carbon black and cork gave a reverse trend. The variation in dielectric properties upon dynamic vulcanization of the rubber phase using different vulcanizing agents (such as sulfur, peroxide, and mixed systems) was also investigated. (C) 1999 John Wiley & Sons, Inc.