Estimation of the agglomeration structure for conductive particles and fiber‐filled high‐density polyethylene through dynamic rheological measurements

Abstract

Abstract A study on the correlation between electrical percolation and viscoelastic percolation for carbon black (CB) and carbon fiber (CF) filled high‐density polyethylene (HDPE) conductive composites was carried out through an examination of the filler concentration (ϕ) dependence of the volume resistivity (ρ) and dynamic viscoelastic functions. For CB/HDPE composites, when ϕ was higher than the modulus percolation threshold (ϕ G ∼ 15 vol %), the dynamic storage modulus ( G ′) reached a plateau at low frequencies. The relationship between ρ and the normalized dynamic storage modulus (G c ′ /G p ′ , where G c ′ and G p ′ are the dynamic storage moduli of the composites and the polymer matrix, respectively) was studied. When ϕ approached a critical value (ϕ r ), a characteristic change in G c ′ / G p ′ appeared. The critical value ( G c ′ / G ′ p)c was 9.80, and the corresponding ϕ r value was 10 vol %. There also existed a ϕ dependence of the dynamic loss tangent (tan δ) and a peak in a plot of tan δ versus the frequency when ϕ approached a loss‐angle percolation (ϕ δ = 9 vol %). With parameter K substituted for A , a modified Kerner–Nielson equation was obtained and used to analyze the formation of the network structure. The viscoelastic percolation for CB/HDPE composites could be verified on the basis of the modified equation, whereas no similar percolation was found for CF/HDPE composites. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1199–1205, 2004