Irrespective of the way a mixing room is laid out, the internal mixer is the heart of the installation. The production capacity of a mixing line and the quality of the compounds produced are determined by the size of the internal mixer and its mixing efficiency. The machine is modular in construction and consists of three major sub-assemblies (Fig. 1.1).
The mixing of rubber compounds is a sophisticated task. Many components are difficult to dose and materials are delivered to the mixer in all thinkable forms, as rubber bales, oils, powders, hard resins, granules, chips, and even pastes. As the conversion of these raw materials into a free flowing form is quite expensive, the discontinuous mixing by a kneader (or batch mixer) is still the most versatile and most economic solution.
In this chapter, the authors try to describe the different principles governing the mixing process. It should be emphasized that in many cases there are also specific requirements and prerequisites for the polymer itself to provide proper mixing results. This chapter shows some examples for the most processed types of polymers used in the rubber industry.
An essential condition for optimum reinforcing properties is good filler dispersion in the rubber compound as this allows best interactions between rubber and fillers. Reinforcing properties have a fundamental influence on the physical properties of the compound and determine the usage properties of rubber ware.
The rubber processing industry today is confronted with increasing economic pressures as well as increasing qualitative demands on the products it manufactures [1, 2]. Consequently, in the manufacture of rubber products it is necessary to continuously open up new potentials to meet these requirements.
The diversified and sophisticated property set of modern elastomers can be achieved by blending polymers having specific physical and chemical properties with particulate reinforcing fillers that are necessary to crosslink the entire system to form homogeneous networks. The incorporation of active fillers into a rubber or rubber blend generates unique improvements in physical properties of elastomers, termed “reinforcement” [1 – 3].
