Rubber blends with varying natural rubber (NR) and polychloroprene (CR) ratio, using carbon black for reinforced, was studied for rubber boot production. The effects of the ratio and the homogenizing agent on the physical and mechanical properties of the blend were investigated. The cure characteristics of the rubber blend reinforced with carbon black were analyzed from the rheographs. Experimental results showed that NR/CR ratio and homogenizing agent affect physical properties of the blend. When the NR/CR ratio was increased the properties of unvulcanisate, i.e. Mooney viscosity, rate of cure and time of cure to 90%, increased. The vulcanisate properties both before and after aging at 100 ํC for 22 h, i.e. specific gravity, modulus, hardness, compression set and ozone resistance, showed considerable improvement by the increase of polychlorprene while elongation at break, oil and grease resistance and anti-static properties decreased. But the tensile strength slightly increased. With regards to mechanicalproperties, the rubber blend appeared to have two glass transition temperatures (T[subscript g]) and tan triangle peaks whereas single rubber showed only one glass transition temperatures (T[subscript g]) and narrower tan triangle peak. However, with addition of homogenizing agent the difference of the two glass transition temperatures (T[subscript g]) of the rubber blend became smaller. This indicated the improved homogeneity of the blend and thus its tensile strength was also slightly increased. When the properties of the rubber blend are compared with the specifications of rubber boot standard, the blend of natural rubber to polychloroprene at 30 : 70 without homogeniaing agent and at 40 : 60 with homogenizing agent meet the standard specifications. Both have been prepared using N660 carbon black as reinforcement and cured with efficient vulcanizing system. Moreover, substitution of natural rubber for polychloroprene saves cost for rubber boot production and increases added value to natural rubber.
