Effects of stearates on the thermal stability of chlorinated natural rubber from latex

The effects of stearates on the dehydrochlorination (DHC) reaction of chlorinated natural rubber (CNR) from latex were studied by the measurement of the HCl evolving rate during the early stage of the thermal degradation of CNR and by the determination of the amounts of cyclic conjugated dienes formed on the CNR molecular chains. During the early stage of the thermal degradation of CNR at 150°C, HCl was eliminated from the CNR molecular chains, and the cyclic conjugated dienes were formed on the CNR molecular chains. Under the effects of barium stearate, lead stearate, cadmium stearate, and calcium stearate, the HCl evolving rates of CNR were reduced, whereas the amounts of cyclic conjugated dienes that formed on the CNR molecular chains were increased. When zinc stearate was added, because of the formation of ZnCl2, which was an active catalyst of the DHC reaction of CNR, both the HCl evolving rate from CNR and the formation of cyclic conjugated dienes were increased. The results indicate that the addition of stearates can reduce the thermal stability of CNR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1981–1985, 2006