Dynamic viscoelastic behavior and molecular mobility of acrylonitrile-butadiene copolymer nanocomposites with various organoclay loadings

Layered silicate nanostructures of NBR nanocomposites prepared using the various organoclays (OCs) and silicate loadings were investigated by analyzing the viscoelastic behavior, activation energy (E-a), and average relaxation times (tau(HN)) obtained from dynamic mechanical measurements. Viscoelastic behavior revealed that NBR nanocomposite with OC having polar organic modifier (NBROC30B) has the highest elasticity in NBR nanocomposites, indicating the formation of the largest gallery height. In addition, E-a and tau(HN) showed that the mobility of NBROC30B was the closest to that of NBR, providing further evidence that NBROC30B has the largest gallery height. Interestingly, viscoelastic behavior, E-a, and tau(HN) of the nanocomposites with silicate loadings in excess of 7 wt% were remarkably higher than those of the nanocomposites with silicate loadings below 7 wt%. These results imply the sudden change of silicate structure and suggest the formation of three-dimensional network-like percolated silicate structure at NBR nanocomposites with silicate loadings over 8 wt%, which was consistent with HR-TEM results.. (C) 2007 Elsevier Ltd. All rights reserved.