Hydrogenated polyisoprene-silica nanoparticles and their applications for nanocomposites with enhanced mechanical properties and thermal stability

Hydrogenated polyisoprene (HPIP)-SiO₂ nanocomposites were synthesized via differential microemulsiion polymerization followed by diimide hydrogenation. First, the isoprene monomer was polymerized on the silane treated nanosilica by differential microemulsion polymerization to obtain polyisoprene (PIP)-SiO₂ nanoparticles with a particle size of 43 nm. PIP-SiO₂ latex was subsequently hydrogenated at the carbon–carbon double bonds by diimide reduction in the presence of hydrazine and hydrogen peroxide with boric acid as promotor to provide HPIP-SiO₂ nanocomposites. Core–shell morphology consisting of silica as the nano-core encapsulated by HPIP as the nano-shell was formed. The highest hydrogenation degree of 98 % was achieved at a ratio of hydrogen peroxide to hydrazine of 1.5:1. The nanosized HPIP-SiO₂ at 98 % hydrogenation showed a maximum degradation temperature of 521 °C resulting in excellent thermal stability, compared with unfilled PIP (387 °C). A new nanocomposite of HPIP-SiO₂ could be used as a novel nanofiller in natural rubber. Consequently, HPIP-SiO₂/NR composites had improved mechanical properties and exhibited a good retention of tensile strength after thermal aging and good resistance toward ozone exposure.