Rheological and electrical properties of carbon black and carbon fiber filled cyclic olefin copolymer composites

Abstract

In this study, morphological, rheological and electrical properties of cyclic olefin copolymer (COC)/carbon black (CB) and COC/carbon fiber (CF) composites were investigated. Rheological measurements indicated that the CB was more effective filler than the CF to improve the viscoelastic parameters such as melt elasticity and dynamic viscosity of samples because of relatively higher surface area and nano size of CB particles. Based on the improvement in melt elasticity of samples depending on the type and amount of filler, the first rheological percolation threshold, the critical filler amount to stepwise change the rheological behavior of composites, were determined to be 9.4 and 15 phr for the CB and CF, respectively. It was also found that the local and continuous agglomeration of CB particles predicted by the Kerner-Nielsen method began at the filler amount of 10 and 30 phr, respectively. The electrical conductivity measurement performed by an impedance spectroscopy exhibited that the electrical percolation was about 15 phr for both fillers. Maximum electrical conductivity vales of 10(-2) and 10(-1) S/cm were obtained by introducing of 40 phr of CB and CF, respectively. (C) 2014 Elsevier Ltd. All rights reserved.