Hydrogenation of natural rubber latex in the presence of OsHCl(CO)(O₂)(PCy₃)₂

Abstract

ABSTRACT:Hydrogenation is an important method of chemical modification, which improves the physical, chemical, and thermal properties of diene elastomers. Natural rubber latex (NRL) can be quantitatively hydrogenated to provide a strictly alternating ethylene-propylene copolymer using a homogeneous osmium catalyst OsHCl(CO)(O 2 )(PCy 3 ) 2 . A detailed kinetic investigation was carried out by monitoring the amount of hydrogen consumption during the reaction using a gas-uptake apparatus. The kinetic results of NRL hydrogenation indicated that this system had a secondorder dependence of the hydrogenation rate on hydrogen pressure and then decreased toward a zero-order dependence for hydrogen pressures above 13.8 bar. The hydrogenation was also observed to be first-order with respect to catalyst concentration and inverse first-order on rubber concentration due to impurities present in the rubber latex. Additions of a controlled amount of acid demonstrated a beneficial effect on the hydrogenation rate of NRL. The temperature dependence of the hydrogenation rate was investigated and an apparent activation energy (over the range of 120 -160°C) was calculated as 57.6 kJ/mol. Mechanistic aspects of this catalytic process are discussed on the basis of kinetic results.

Improving thermal and ozone stability of skim natural rubber by diimide reduction

“…Thus, the two glass transition temperatures observed for HSNR confirmed the layer model morphology for the hydrogenation as discussed in the previous section regarding the TEM study. Compared with the complete HNR produced from hydrogenation in the presence of OsHCl(CO)(O 2 )(PCy 3 ) 2 , all DSC thermograms of 99% HNR samples indicated the one step base-line shift at À61.8 C [17] and À59.6 C [18]. This implies that the HNR prepared from catalytic hydrogenation has a single glass transition temperature.…”

“…[15][16][17][18][19], the extent of hydrogenation increased with increasing rubber concentration up to 0.55 M and then decreased. At high rubber concentration, the diimide species may self-decompose during the hydrogenation process resulting in a low degree of hydrogenation.…”

ABS modified with hydrogenated polystyrene‐grafted‐natural rubber

“…Hydrogenation of NR can be achieved by both catalytic [4][5][6][7][8] and noncatalytic methods. Hydrogenation of NR can be achieved by both catalytic [4][5][6][7][8] and noncatalytic methods.…”

Katalitik transfer hidrogenasi lateks karet alam dengan senyawa diimida pada skala semi pilot

“…Cifriadi et al (2017a) mempelajari pengaruh rasio konsentrasi hidrasina hidrat/hidrogen peroksida pada reaksi hidrogenasi lateks pekat berpengawet NaOH pada suhu 70 o C. Dari hasil riset diketahui bahwa bertambahnya dosis hidrogen peroksida menyebabkan terbentuknya reaksi samping depolimerisasi pada molekul karet alam akibat terbentuknya radikal bebas hidroksil dari sisa hidrogen peroksida yang tidak bereaksi. Temuan ini sejalan dengan hasil riset sebelumnya yang telah dilakukan oleh Lin et al (2004) dan Mahittikul et al (2006). Sistem penstabil lateks dengan surfaktan anionik SDS pada reaksi hidrogenasi lateks DPNR berkatalis (asam borat, tembaga sulfat, dan tembaga asetat) turut dipelajari oleh Cifriadi et al (2017b).…”