Conveying
– The polymer sticks to the screw and slips on the barrel (No
transport)
– The polymer resists rotation in the barrel and slips on the screw
(Be transported)
■ The friction of screw & barrel leads to drag flow
■ The pressure gradient along the extruder generates pressure flow
■ The space between screw & barrel causes leak flow (material leaks
backward)
Total flow = drag flow-pressure flow-leak flow