Abstract: Hydroxy-terminated butadiene-acrylonitryle copolymer (HTBN) was synthesized by using H₂O₂ as initiator. Four samples of HTBN with, f_n=1.94, 2.32,2.64 and 3.02, respectively,were prepared by adding HOCH₂CH₂SH or 2-hydroxyethyl acrylate during polymerization.Isophorone diisocyanate (IPDI) was used as curing agent and N,N'-bis(hydroxypropyl)aniline (Isonol C-100)as chain extender.The results showed that the curing rate is dependent on f_n, the higher the f_n, the faster the rate. The crosslinking density of the cured rubber increascs with increasing f_n, showing influence on the properties of the rubber. The tensile strength and hardness increase with increasing f_n, with the elongation being decreased.HTBN elastomer with f_n=1.93 is found to be a promising damping material due to the constant tanδ over a wide temperature range. Two transition temperatures were observed for all HTBN rubbers studied. Increase of f_n is of benefit to the oil- and heat resistance of the cured rubber.