Short flow milling process

Even with emulsion polymerisation, polyethylacrylate rubber tends to go into Region IV of mill processability, i.e., the flow region. This is because the rubber has 73% of its MW as the pendent group. It is a fat and short molecule compared with diene rubber. The presence of some long branches may help mill processability. However, when the tendency for Region IV behaviour is known, upside-down mixing, i.e., charging carbon black first into an internal mixer and then the rubber, is the usual practice. 

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