Hydrogenated nanosized polyisoprene as a thermal and ozone stabilizer for natural rubber blends

Hydrogenated polyisoprene (HPIP) nanoparticles, synthesized via organic solvent-free hydrogenation using RhCl3/TPPMS as a catalyst, are novel nanofillers for natural rubber (NR) blends. Hydrogenation of a polyisoprene (PIP) emulsion was carried out in a Parr reactor. Rhodium trichloride (RhCl3.3H2O) and monosulfonated triphenylphosphine (TPPMS) were used as the catalyst precursor. The HPIP was characterized by proton nuclear magnetic resonance spectroscopy. The PIP hydrogenation in the absence of organic solvent is a first-order reaction with respect to carbon-carbon double bond concentration, and the rate constant was dependent on catalyst concentration. The highest hydrogenation degree of 93% was achieved at a catalyst concentration of 250 μM with a reaction time of 12 h. The NR/HPIP blends (blend ratio = 80:20) after thermal aging show high % retention of their tensile strength and modulus, maintaining 94.5% and 93.7%, respectively. Moreover, a combination of HPIP in NR improved the ozone resistance at the surface of the rubber blends. Therefore, the NR/HPIP composite exhibited a good retention of tensile properties after thermal aging and good resistance toward ozone.