Due to the differences in unsaturation levels of constituent rubbers, thioacetate and mercapto functional groups were introduced into hydrogenated natural rubber (HNR) to increase the compatibility of natural rubber (NR)/HNR blends. The effect of thioacetic acid and initiator concentrations including reaction time on the thioacetate content in HNR was investigated. Methanolysis of thioacetate-modified HNR (HNRTA) yielded mercapto-modified HNR (HNRSH). The addition of HNRTA or HNRSH into NR/HNR blends (50/50 wt ratio) increased the tensile strength. The improved mechanical properties of the compatibilized blends were confirmed by scanning electron microscopy, indicating a co-continuous morphology. Furthermore, the susceptibility of the vulcanizates to changes in temperature and ozone were also reported. (C) 2010 Elsevier Ltd. All rights reserved.