Mixing methods, additives influence compounds

Although there has been much development and discussion regarding the use of silica as an alternative to carbon black as filler, in practice the usage is not fully adopted. Many applications are met by use of both silica and carbon black, often blended together in the same compound. There are several good reasons for doing this; cost and productivity often are mentioned. These compounds are not without processing problems though, and again while much work has benn published concerning silica processability, less has been written about applications where a blend of fillers is used. But process additives can help. The experience gained in overcoming the mixing and extrusion production problems associated with high-silica loadings together with the long history of process additive usage in carbon-black filled compounds can be combined to maximize the production efficiency in these cases. This review paper looks at some alternative routes to producing these compounds and highlights the impact that surfactant-based process additives can have on improved productivity and compound quality. It was found that different mixing methods and the point of the process additive addition had a big influence on the mixing productivity and the extrusion performance. Final properties also were influenced.