Effect of LiBr Concentration on Carbonation of Natural Rubber with Supercritical Carbon Dioxide

The effect of LiBr concentration on carbonation of natural rubber was investigated in relation to the miscibility of LiBr and liquid deproteinized natural rubber having an epoxy group (LEDPNR) as a source. LEDPNR was prepared by epoxidation of deproteinized natural rubber with peracetic acid followed by depolymerization with ammonium persulfate. It was incubated with supercritical carbon dioxide at 403 K for 6 h, after mixing with various amounts of LiBr. The products were characterized through 1H NMR, 13C NMR, two-dimensional correlation spectroscopy (COSY), and two-dimensional heteronuclear correlation (HETCOR) spectroscopy. The conversion and the carbonate unit content of the products were associated with the LiBr concentration. The effect of LiBr concentration on the carbonation of natural rubber was interpreted separately in the miscible state and immiscible state.