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.