CARBON-BLACK DISTRIBUTION IN NR POLYBUTADIENE BLENDS

The distribution of carbon black between the phases of a NR/cis-1,4-po lybutadiene (BR) blend was studied. An N550 carbon black was added to the blend using different mixing techniques. The carbon-black distribu tion was determined using a variety of analytical techniques. The crys tallization temperature of the BR was measured by differential scannin g calorimetry. This temperature is related to the carbon-black level i n the BR phase. Samples were dissolved in toluene to separate the boun d and soluble rubber portions and the fractions were analyzed for poly mer type and amount by solid state C-13 MAS nuclear magnetic resonance . Results indicated that the N550 black has no preference for either t he NR or the BR. In phase mixed samples, the majority of the black rem ains in the polymer to which it is initially added. When black and pol ymers are mixed simultaneously, the black tends to distribute itself u niformly between the polymers. Physical test results on a typical side wall compound indicated that the location of the carbon black has a si gnificant effect on physical properties, especially cut-growth resista nce.