Sales Information

RANDCASTLE
EXTRUSION SYSTEMS, INC.
SFEM BATCH MIXERS:
Peer Reviewed Technical Papers:
 “FACILE TPO DISPERSION USING EXTENSIONAL MIXING,” presented by
Dow Chemical’s Stéphane Costeux at Antec 2011 concluded:
Simply put?
1. “…the Randcastle SFEM batch mixer indicate that its dispersive capabilities are superior
to the Mixing Bowl, while reducing the amount of material and time per blend.
2. It is confirmed that the SFEM’s primary deformation mode is elongational, which also
contributes to limiting shear heating effects.
3. The same SFEM elements can be added to a single screw extruder, which achieve even
better performance, which is encouraging from a scale-up standpoint.
4. This technology is suitable for single-screw extrusion of TPOs and other immiscible
blends.
 “A NOVEL MICRO-BATCH MIXER THAT SCALES TO A SINGLE SCREW
COMPOUNDER,” written with Rutgers University’s Jennifer Lynch and Tom Nosker
Simply put?
for Antec 2008, the paper concludes: The micro-batch mixer is shown to produce similar
mixedness as the SSE for a variety of materials systems because of its similar geometry to the
SSE compounder with SFEM elements. The mixing times are fairly short and comparable to
extrusion residence times. This micro-batch mixer adds a powerful tool for the polymer
researcher because only small quantities of material are necessary, and these experiments
successfully scale-up to large-scale extrusion processing equipment. The micro-batch mixer is
a vital, simple piece of equipment that provides results quickly and conveniently.
RANDCASTLE EXTRUSION SYSTEMS, INC.
SFEM BATCH MIXERS: Elongational batch mixers from 1 to 200cc capacity:
Dispersity 10 times better than “mixing bowls.”
Mixtures (below left) in one third the time of “mixing bowls.”
Compounding equal to a twin screw extruder.
Scales to our single screw mixers (same geometry).
Conveniently extrudes your material into a strand:
 No need to scrape melted material from hot rotors.
Continuous: 20PS/80HDPE Globules
 Quick strand cooling eliminate degradation.
Domains: 0.2 to 2 Micron
Randcastle
 No need to grind scrapings for later processing.
Randcastle
SFEM Batch
SFEM Screw
 Find details in peer reviewed technical papers.

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Stéphane Costeux , Dow Chemical
Mark Barger, Dow Chemical, et al
FACILE TPO DISPERSION USING
EXTENSIONAL MIXING
Antec 2011 (left)
Keith Luker, Randcastle
Jennifer Lynch, Rutgers University
Tom Nosker, Rutgers University
A NOVEL MICRO-BATCH MIXER
THAT SCALES TO A SINGLE
SCREW EXTRUDER
Antec 2008 (right)
(A)
(B)
(A)
(B)
(C)
(D)
(C)
(D)
Co-Continuous: 30PS/70HDPE
(E)
(F)
(E)
(F)
(G)
(H)
(G)
(H)
RANDCASTLE
EXTRUSION SYSTEMS, INC.
MODEL NUMBER
BARREL ID INCH
ROTOR L/D
~INPUT CC
~EXTRUDED OUTPUT
SFEM-BM-2500-4
2.5
4
200
100
SFEM-BM-2500-2
2.5
2
100
50
SFEM-BM-2500-1
2.5
1
50
25
SFEM-BM-2000-4
2.0
4
100
50
SFEM-BM-2000-2
2.0
2
50
25
SFEM-BM-2000-1
2.0
1
25
12
SFEM-BM-1000-4
1.0
4
10
5
SFEM-BM-1000-2
1.0
2
5
2.5
SFEM-BM-1000-1
1.0
1
2.5
1.25
SFEM-BM-0750-4
0.75
4
5
2.5
SFEM-BM-0750-2
0.75
2
2.5
1.25
SFEM-BM-0750-1
0.75
1
1.25
0.6
close up
extrusion
Study May Boost Prospects
For Single-Screw ‘Elongator’
Has the heated debate over whether a single
screw can possibly provide elongational
mixing akin to a twin screw now been settled?
Dow Chemical Co., Midland, Mich., weighed in at last year’s SPE
ANTEC (May 1-5 in Boston) with a paper discussing results of
experiments it conducted on a novel elongational mixing device
developed by Randcastle Extrusion Systems, Cedar Grove, N.J.
The paper, delivered by Dow researcher Stephane Costeux,
discussed the results of mixing tests using Randcastle’s SFEM series
batch mixers versus a batch-mixing bowl, both running TPO
blends of 70% polypropylene and 30% ethylene copolymers. The
batch mixer had the same basic geometry as Randcastle’s SFEM
patented elongational mixer for single screws, introduced in 2008.
Dow’s testing confirmed that where typical batch mixers are
shear-dominant, the Randcastle mixer has “stronger extensional
flow” to achieve better TPO dispersion. The Dow study also used
a Randcastle single-screw extruder with similar mixing geometry
to determine that the “SFEM’s primary deformation mode is
elongational (as opposed to shear-dominated),” and added that “a
single-screw extruder equipped with SFEM mixing elements
achieved even finer dispersion, usually achievable only with twinscrew extruders.”
Keith Luker, president of Randcastle (randcastle.com), has
been touting the elongational mixing capabilities of his device
since he first developed it. The response, by and large, has been
skeptical, as twin-screw extruders are generally considered the
gold standard where mixing is concerned.
“Elongation is a stretching force; its opposite is compression,”
explains Luker. “Compression pushes material together, as in the
compression section of a screw. If you take a cylinder and push on
it from all sides nothing will happen. Take the same volume of a
cylinder and stretch it out into a film, and you get an exponential
increase in surface area. That quantifies the mixing improvement.
The key is the pulling surface that stretches material from the inlet
channel—just as nip rolls pull.” (See illustration of how it works.)
The Dow paper also addressed the matter of scale-up: “The
most important attribute of mixing equipment used to make such
small-scale blends is that it achieves a degree of mixing or morphology that is consistent with that obtained with large-scale
compounding equipment. If the geometry of the batch mixer is
How the Elongational Mixer Works
1
ing
Pull
ing
Pull
r
to
Vec
Sur
A cylindrical concentration of unmixed
material (purple) enters the first channel
pushed along by pressure flow by
upstream flights. It is immediately grabbed
by the moving pulling surface-just as pull
rolls would grab your finger.
s
face
Pressure flow pushes the
material along the inlet
while pulling surface and
drag flow begin to convert
the cylinder into a film.
2
3
The concentration nears total conversion to film. The actual film is much
longer than depicted because the drag
velocity is much higher than that inlet
channel velocity.
very different from the mixing-element geometry of the largescale process (often involving a single-screw extruder), translation
of laboratory formulation results to commercial scale becomes
extremely challenging.”
But Luker notes that the batch and screw SFEM mixers have
essentially the same geometry. “You expect the same geometry to
scale up,” states Luker. “You do not expect mixing-bowl geometry to scale up to because it does not resemble a single screw.”
Luker notes that a previous paper delivered at ANTEC 2008
by Drs. Jennifer Lynch and Tom Nosker of the Dept. of Ceramic
and Materials Engineering, Rutgers University, New Bruswick,
N.J. confirmed the scale-up from batch mixer to extruder screw.
Commercial applications of Luker’s SFEM elongational mixer
to date include mixing of 35% calcium carbonate in a directextrusion application; mixing immiscible materials for pipe;
mixing large mica flakes for pearlescent compounds; and blending
high- and low-viscosity polymers.
Luker says it takes only two mixing sections in a 24:1 LD
screw to get about 125 times better mixing, or three mixers in a
32:1 LD to give you about 1000 times better mixing, than with a
standard single screw.
By James J. Callari, Editorial Director
Plastics Technology january 2012 11