Molecular dynamics in chlorinated butyl rubber containing organophilic montmorillonite nanoparticles

The dynamic mechanical loss tangent (tan delta) of chlorinated butyl rubber (CIIR) shows an asymmetrical double-peak structure with a shoulder on the low-temperature side and a maximum on the high-temperature side, which are attributed to local segmental motion and Rouse modes, respectively. To study the effect of nanoparticles on these two different modes of molecular motion, organophilic montmorillonite nanoparticles (OMMT) were incorporated into CIIR. With the increase of OMMT weight fraction, a filler network is formed and becomes more and more compact in the CIIR matrix, which exerts significant effect on the molecular dynamics of CIIR. The maximum and the shoulder of the tan delta peak are both suppressed by the filler network, but the maximum is suppressed to a higher extent and finally even becomes lower than the shoulder at high filler loading. The temperature position of the maximum is also shifted toward lower temperature with the formation of the filler network, while that of the shoulder remains nearly constant. These phenomena can be interpreted in terms of the different restriction extents of the filler network on the different modes of molecular motion.