Viscoelastic behaviour of rubber in an internal mixer

Reprinted with permission from N. Nakajima, internationai Poiymer Processing, 1996, 11, 1, 3. Copyright 1996, Hanser Pubiishers, Munich. 

As explained in Chapter 2 the most desirable behaviour of rubber in the mixing process is described by Region II of mill processability [4]. Rubber in this state is elastic and gives a large deformation without break. 

Reprinted with permission from N. Nakajima, internationai Poiymer Processing, 

Mooney used a parallel plate rheometer with a piece of ruhher, with one surface which was dyed. As the rotation continued, the colour of the dye was observed to spread in the direction of thickness of the specimen. The fractured rubber particles, as they rotated under the shear field, carried the dye like an ink-roll. This process imprinted the dye from the surface down to the successive layers of the rubber particles. On the basis of this model Mooney calculated the size of the rubber particles, i.e., the flow unit to be of the order of 10 pm [9]. Mooney s model on the generation of super-molecular flow units is one of models used as the basis for proposing the comminution model for mixing of rubber with fillers [10]. 

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