Experiments and modeling of non-linear viscoelastic responses in natural rubber and chlorobutyl rubber nanocomposites

摘要

The filler-filler and rubber-filler interactions in polyisoprene (natural rubber - NR) and chlorine substituted poly isoprene-isobutyl rubber (chlorobutyl rubber - CIIR) were monitored by non-linear viscoelastic measurements (Payne effect). The experimental results have been modeled using the famous Maier-Goritz equation and by the tradition approach of Kraus theory. It was observed that the filler-filler network formation in NR/organoclay nanocomposites was very strong while the interactions in CIIR/organoclay nanocomposites were very poor. The network formation and dispersion of nanoclay platelets were observed using AFM and TEM techniques. Using the DSC technique, the effects of filler-filler and filler-polymer interactions on glass transition temperature (T-g), confinement of polymer chains (chi(i)) and the variations in heat capacity (Delta Cp) were analyzed. These analyses revealed that the nanofiller loading in rubber matrix developed a rigid amorphous region due to the confinement of polymer chains. The T-g of the natural rubber nanocomposites was increased and then decreased as the filler loading increased from 0 to 10 phr. The mechanical percolation behavior of rubber nanocomposites were estimated using the Huber-Vilgis approach by calculating the excess modulus. The application of this approach pointed out to a cluster-cluster aggregation model (CCA), where space filling clusters were formed. The diffusion of liquids through the nanocomposites was carefully evaluated for explaining the nanofiller interaction with the two rubber matrices. Finally, the Kraus, Lorentz-Parks and Cunneen-Russell models were applied to quantify the degree of reinforcing action of the fillers in both elastomer matrices. (C) 2016 Elsevier B.V. All rights reserved.