The Energy Aspects of Mixing Rubber

10.1 Introduction
The energy aspects of rubber mixing have been a focal point of some research activity.
Particular attention has been given to the process involving internal mixers. A state-ofart
review was published on this subject [1]. A method was proposed for control and
scale-up which was based on the energy input for mixing [2]. Those properties affected
by the degree of mixing were evaluated as functions of mixing energy [2, 3, 4]. This
method was used for evaluating the performance of different types of elastomers and
carbon blacks in internal mixers [5, 6]. Although the method treats the internal mixers
essentially as a ‘black box’, it represents significant progress in understanding the mixing
process. It permits comparison of the efficiency of different types of equipment and the
evaluation of the ease of mixing of a given formulation.
The energy aspect is not only of technological importance but also an economic concern.
It leads to two questions: how the input energy is spent and how much is actually necessary.
The answer to the first question is to take an energy balance, which is a method of ‘book
keeping’ on the income and expenditure in terms of energy. The second question requires
elucidation of mixing mechanisms and calculation of theoretical energy requirements.
The mill-mixing involves human participation. Therefore, the energy spent in the machine
operation is only a part of the overall energy aspect. It is not easy to quantify the energy
balance. On the other hand mixing with an internal mixer is amenable to taking energy
balance. The foregoing discussion is about the operation of internal mixer only and an
example is a Banbury type mixer.
The examination of mixing mechanisms will also deal primarily with the internal mixer,
because the energy requirements must be determined quantitatively. A discussion of this
subject will be given in Chapter 11.