The interest in these machines for rubber compounds has been brought about
by improvements, which include increases in maximum torque levels and in the permissible
free volume (fill factor) [35]. The former is required to accommodate the high viscosities
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of rubber compounds while the latter is important for efficient cooling. Berstorff have
reported successful single-pass mixing of a 90 ML(1+4) EPDM compound, with an output
rate of 500–600 kg/h and an exit temperature of 130–135 °C from a machine with a
90 mm screw diameter. It is mentioned that chilled cooling water circulation was necessary
to achieve this result [