Carbon black dispersibility

Fig. V-8. Electrophoretic mobility of carbon black dispersions in 10 KNO3 as a function of pH. (From Ref. 93.)...

In the depolymeri2ed scrap mbber (DSR) experimental process, ground scrap mbber tines produce a carbon black dispersion in ok (35). Initially, aromatic oks are blended with the tine cmmb, and the mixture is heated at 250—275°C in an autoclave for 12—24 h. The ok acts as a heat-transfer medium and swelling agent, and the heat and ok cause the mbber to depolymeri2e. As more DSR is produced and mbber is added, less aromatic ok is needed, and eventually virtually 100% of the ok is replaced by DSR. The DSR reduces thermal oxidation of polymers and increases the tack of uncured mbber (36,37). Depolymeri2ed scrap mbber has a heat value of 40 MJ/kg (17,200 Btu/lb) and is blended with No. 2 fuel ok as fuel extender (38). 

Fig. 1. Effect of primary particle size in a 1% carbon black dispersion on rate of change in reflectance. O = min = 20 min 3 = 180 min ...

Incidentally, as is well known, in the unvulcanized state of the filled mbber, the stress upturn does not appear even in the carbon content of = 0.2-0.25. For understanding this phenomenon, we must consider the discontinuity between the SH layers, in addition to the very low modulus of the unvulcanized mbber. Actually, as we discussed earlier, carbon blacks disperse as an aggregate of carbon particles, then the continuity of carbon gels consisting of aggregates must be much poorer than the theoretical calculation based on the perfect dispersion of carbon particles. In this case, the stress cannot be transmitted from carbon gel to carbon gel through such a very soft medium, and as a result, the stress-strain curve of the system is rather similar to the characteristics of the... 

New Technology for Carbon Black Dispersion in Rubber—Continuous... 

An enormous amount of work has been reported on the issue of carbon black dispersion improvement. One of the approaches has been to produce carbon black-polymer masterbatches by mixing... 

Electrical Conductivity of Carbon Black Dispersions in Podecane(16)... 

Figure 9. Zeta-potential of carbon black dispersed in dodecane with OLOA-1200 dispersant (23°C.). Sampled from dispersions of 3.33 g of carbon black per liter of dodecane. Reproduced with permission from Ref. (14). Copyright 1983, Elsevier Science Publishers.

Studies on the kinetics of carbon black dispersion in various rubbers have been reported using a Brabender mixer fitted with cam-type rotors [110]. Dispersion rating, determined by visual inspection of photomicrographs, was found to depend strongly on mixing time. For an SBR emulsion, it was observed that there was an initial delay period where the carbon black agglomerates were thought to be fractured and incorporated into the rubber. Subsequently, the process of dispersion continued for a considerable time thereafter. 

ISO 11345 1997. Assessment of carbon black dispersion - Rapid comparative methods. 

Incident—Is used to examine surfaces of bulk samples, e.g., carbon black dispersion in rubber compounds. (Figure 5)... 

Figure 5. Light microscopy incident light carbon black dispersion in rubber. 

Figure 39 Correlation of Lll signal decay time and primary particles size measured by TEM for different carbon blacks dispersed in ethanol (Sommer and Leipertz,...

The quality requirements of dispersive mixing generally require that the fraction of agglomerate above a critical size be below a certain set value. For carbon black dispersion in rubber, for example, generally the requirement is that the fraction of agglomerates above 10 pm be less than 1%. In terms of distribution function the mixing time needed to meet such a... 

If Tl and 1/5 are plotted as ordinate and abscissa, we get curves of different types. The intercept on the K-axis will give the value of T)rt, i.e., resistance of flow at extremely high shear ratio. It has been observed that thixotropy of carbon black dispersion is reduced on adding 3% linoleic acid. These curves also show the effect of thixotropy in the absence and presence of linoleic acid, respectively. 

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