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Reader’s Queries on Extruders, Elements,
Polymer-Compounding etc are answered
by ET’s Expert Group
Answer for ET 7
QUESTION YOU
Q 1. What are the key benefits of a lab
extruder?
Q 2. Why are lab extruders increasingly
becoming a necessity in industries and
universities?
The best answer will be published. Readers
are
to send-in their answers with
appropriate drawings / pictures / illustrations
to
The ET expert panel, would SELECT the most
appropriate answer. ET's decision is final.
The participant to send full name and address
particulars along with their answers.
LAST DATE to receive the entry is
May 31, 2009.
INVITED
etec@extrudertimes.com
How to obtain good elongational flowof polymers in a Twin-ScrewExtruder?
In a co-rotating Twin-Screw Extruder, mixing takes place
as a result of Shear Flow and Elongational Flow.
Increasing the flow velocity of the melt in taper cross
sections will result in stretching of the melt thus giving
elongation effect. In a twin-screw extruder, this can
take place in axial as well as circumferential direction.
STEER's Fractional Mixing Element (FME) is a Long Lead Element and has a Fractional Lobe
Geometry. The Fractional Multi Lobe Geometry of the FME causes an axial reduction in the
flow cross section and creates a tapering gap in the circumferential direction resulting in an
elongational flow in the melt by the rotating action.
Effects of Elongational Flow: In case of higher molecular weight particles or agglomerates, it
is necessary to first break them down. This is achieved by elongational flow. More the
Elongation, higher are the forces acting on the agglomerates causing the clusters in the melt
to break down thus giving better dispersion of the material.
Answer provided by: Mr. Durgesh Bakshi
Ref. Co- Rotating Twin-Screw Extruders, Fundamentals,
Technology and Applications.
Klemens Kohlgrüber - Hanser Publishers.
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Brainstorm invites questions
P l e a s e s e n d y o u r q u e s t i o n s t o
etec@extrudertimes.com
‘Most people live in a very restricted circle of
their potential being. We all have reservoirs
of energy and genius to draw upon of which
we do not dream.’
William James
‘If you have built castles in the air your work
need not be lost; that is where they should be.
Now put the foundations under them.’
Henry David Thoreau
Plastics technology and co-rotating extruders
have undergone dramatic
developments which, to a certain extent, have been synchronous and mutually supportive.
Plastics technology has profited from the increasing potential of the co-rotating extruder,
while polymer technology has itself been a hothouse for advances in co-rotating extruders.
Conclusion: "There is hardly a kilogram of plastic today that has not encountered a co-
rotating extruder somewhere on its journey between polymerisation and processing "
Source: A book on Co-Rotating TSE by Klemens Kohlgrüber - HANSER
FME