An Approach to the Modeling of Mixing of Elastomers

Abstract

Abstract In recent years, the process of mixing elastomers with carbon black has been the subject of various studies. In particular, the process involving the use of the internal mixer has been examined systematically, and Palmgren has published a general review on the state of the art. A method was proposed for the control and scale-up which is based on the energy input for mixing; then, properties were evaluated as a function of the mixing energy. This method was used for evaluating the performance of different types of elastomers and carbon blacks in the internal mixer. Although the method represents significant progress in understanding the mixing process and is of practical importance, it still treats the mixer essentially as a “black box”. In order to elucidate the mechanism of mixing, visualization must be performed. One type is static visualization, in which the machine is stopped at an intermediate stage and the contents are taken out for inspection. Another is dynamic visualization through transparent walls of a mixer. These observations enable us to construct a model for the deformation-flow behavior of materials and a model for the mixing mechanism. These models, in turn, guide us to laboratory measurements of the material behavior which are pertinent to the mixing mechanisms. With respect to mill processability, Tokita and White classified raw material behavior into four regions, which are functions of a given material and dependent on the time scale, temperature, and magnitude of strain. This classification is applicable not only to the millability of the raw elastomer but also to the ease of mixing with carbon black. This interpretation may be extended to the processability of the material in the internal mixer.