Nanocomposites based on chloroprene rubber: Effect of chemical nature and organic modification of nanoclay on the vulcanizate properties

The effect of two chemically opposite type of nanofillers, namely montmorillonite (MMT) and layered double hydroxide (LDH), both in pristine and organically modified forms (OLDH and OMMT) on the mechanical properties and crystallization behavior of chloroprene rubber (CR) vulcanizates have been investigated. While the addition of very small amount of pristine clays shows a significant improvement of the physical properties of the CR based nanocomposites, the organic modification improves the reinforcing efficiency of MMT more than that of LDH. MMT is found to enhance the crystallization tendency of CR chains, whereas LDH has a role to resist it as observed from the dynamic mechanical analysis (DMA). The DMA results also show that the presence small amount of nanoclay enhances the storage modulus of CR based vulcanizates, which becomes more pronounced in case of organically modified clays, especially with OMMT. Finally, we report the ‘house of cards’ structure of exfoliated platelets of montmorillonite in the CR matrix which are produced by mechanical shear mixing.