Experiments have been carried out on a 38-mm diameter single screw extruder in which the machine was fed at a controlled rate below its capacity (the starve fed mode). It was found that, for three different polymers in granular form, the die pressure fluctuations and specific power consumption reduced for limited amounts of starvation and these improvements were associated with a smoother melting profile. Melt initiation was delayed but once it had started subsequent melting was rapid. Higher levels of starvation with granules and also modest degrees of starvation of a polyethylene powder had deleterious effects. The observed behavior is discussed in terms of the increased solid bed mobility allowed by the loosely packed material in the screw channel.

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