Frequency-dependent scaling behavior of polyvinylidene fluoride/metal composites

Abstract

The frequency-dependent percolation and scaling behavior of a variety of polymer/metal composites (PMC), based on polyvinylidene fluoride (PVDF) matrix and various types of fillers such as; metal/alloy particles of different sizes, prepared through cold/hot pressing process conditions have undergone investigation. The universal percolation behavior in the vicinity of percolation threshold ([Formula: see text]), i.e., [Formula: see text] and [Formula: see text] is well satisfied, which suggests [Formula: see text] to be independent of frequency, where [Formula: see text] and [Formula: see text] are the effective ac conductivity and effective dielectric constants of the composite and [Formula: see text] is the frequency of applied ac signal. The obtained experimental values of the exponents are consistent with the inter-cluster polarization model ([Formula: see text] and [Formula: see text]), satisfying [Formula: see text]. The widely used percolative equations are well fitted with the experimental results of all PMC at all values of the frequency. The value of [Formula: see text] is found to be independent of frequency of the applied signal, suggesting the studied PMC are real percolating systems. The critical exponents ([Formula: see text] and [Formula: see text]) which characterize the divergence of [Formula: see text] and [Formula: see text] in the vicinity of [Formula: see text] are found to decrease with the increase of frequency. The rate of decrease of ‘[Formula: see text]’ and ‘[Formula: see text]’ with increase of frequency is attributed to the method of preparation, size of the fillers, adhesiveness of polymer/filler and the rate of decrease of [Formula: see text] with frequency (due to the absence of different extents of contributions of various types of conventional polarizations).