HANSER Hanser Publishers, Munich • Hanser Gardner Publications ...
HANSER Hanser Publishers, Munich • Hanser Gardner Publications ...
HANSER Hanser Publishers, Munich • Hanser Gardner Publications ...
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we get<br />
The dimensionless parameter is the ratio between the amount of melted polymer per<br />
unit down channel distance to the extruder output per unit channel feed depth.<br />
5.23.4 Melting Profile<br />
The melting profile provides the amount of unmelted polymer as a function of screw<br />
length (Figure 5.25) and is the basis for calculating the stock temperature and pressure.<br />
It thus shows whether the polymer at the end of the screw is fully melted. The plasticating<br />
and mixing capacity of a screw can be improved by mixing devices. Knowledge of the<br />
melting profile enables to find the suitable positioning of mixing and shearing devices in<br />
the screw [21].<br />
The following equation applies to a screw zone of constant depth [6]<br />
and for a tapered channel [6]<br />
where<br />
X<br />
W<br />
Screw<br />
t<br />
X<br />
W<br />
Axial distance along the screw<br />
Cross-section of screw channel<br />
Figure 5.25 Solid bed or melting profiles X/W and Gs/G [21 ]<br />
G: total mass flow rate, G5: mass flow rate of solids<br />
X/WA/G<br />
Melt Solid bed Melt film<br />
Barrel<br />
(5.57)<br />
(5.58)<br />
(5.59)