The Segregation Behavior Of Carbon Black In Low Hardeness Nr/Br Blends

Segregation behavior refers to the phenomenon of uneven distribution ofchemical composition. In the field of rubber processing, segregation behavior refersto the uneven distribution of reinforcing filler, such as carbon black, silica, carbonfiber, etc., in rubber matrix. In this paper, the segregation behavior of carbon blackin the low hardness nature rubber (NR)/Polybutadiene rubber (BR) blends werestudied by using RPA, DMA and TEM methods. The effect of many factors such ascarbon black types (N330and N550), BR types (Buna CB24and BR9000), NR/BRratio and mixing procedures on the distribution of carbon black and other propertiesof NR/BR blends were systematically investigated..For NR or BR, the addition of carbon black may shorten the scorch time t10andthe optimum cure time t90, which means that carbon can accelerate the vulcanizationreaction of NR or BR. For the same carbon black, the influence of carbon blackaddition on the cure characterizes of BR was more obvious than NR, for the samerubber, the acceleration effect of N330was more obvious than N550. The addition ofcarbon black lowered the peak height of the damping factor (tan) of NR and BRvulcanizates, and a linear behavior between the reduction of the peak height of tan and the content of carbon black was observed. But the glass transition temperature(Tg) of the NR or BR vulcanizate didn’t change when the content of carbon blackchanged.In the NR/BR9000(50/50) blends, the mixing procedure could change thedistribution of carbon black N330in NR phase and BR phase. The content of N330inBR phase was much more the NR phase. When mixing procedure BR+CB was used,in which carbon black was premixed with BR, the segregation of carbon black inNR/BR was most obvious, by contrast, the distribution of carbon was most evenlywhen NR+CB procedure was used, in which carbon black was premixed with NR.The Payne effect and heating build-up of NR/BR9000prepared by NR+CB werelowest. The segregation behavior of carbon black in NR/BR blends was also affected bythe BR types. Compared with NR/BR9000blend, the mechanical properties and tan of vulcanizate of NR/Buna CB24was much better. At the same time, the segregationof carbon black in the blend thus the Payne effect of NR/Buna CB24was lower thanNR/BR9000.The blend ration of NR/Buna CB24could affect the segregation of carbon black.The DMA results showed that the compatibility of NR and CB24was improvedwhen the NR content decreased. For all NR/BR blend ratio tested in the experiment,the affinity between carbon black and BR was higher than carbon black and NR, BRpreferred to migrate into the BR phase. As the BR content in the blend decreased,more carbon black distributed in NR phase, and when the NR/BR ratio is70/30,carbon black distributed in NR and BR phase evenly.Compared with N330, carbon black N550tend to migrate into BR phase too, butsegregation behavior of N550in NR and BR phase was less obvious than N330.