A novel synthetic route to natural rubber/montmorillonite nanocomposites using colloid stabilization–destabilization method

A novel synthetic route to the highly-loaded rubber nanocomposite was developed by a stabilization–destabilization process of colloidal mixtures using montmorillonite (MMT) and natural rubber (NR) as a model system. By analyzing the zeta potentials of the MMT and NR colloids, the stable and unstable conditions of their mixture were identified and subsequently used as the mixing and precipitating process conditions, respectively. The NR drops and MMT nanoplatelets were homogeneously mixed due to their electrostatic repulsion in the stabilized condition of pH > 10.5 and, then the stabilized colloidal mixture were forced to precipitate quickly by changing to pH < 4.0 for destabilization, where the surface charge of the NR drops became positive and attracted the negatively-charged MMT particles resultantly to coagulate together. The developed methodology enabled a maximum loading content of MMT up to 25 phr (20.0 wt%) with a surprisingly large increment in mechanical properties: e.g., tensile modulus by 198% and tear strength by 69%.