Three roll mills are the most versatile dispersing system in use today, and because of its process-related benefits, it's often the only solution. EXAKT has redefined the three roll mill for laboratory, research, and production.
1. 1because precision matters.
DISPERSING WITH
THREE ROLL MILLS
Introduction
EXAKT Technologies
7002 N. Broadway Extension
Oklahoma City, OK 73116
800-866-7172
info@exaktusa.com
www.exaktusa.com
2. 2because precision matters. Dispersing with Three Roll Mills _ Introduction
1. Introduction
2. Definition of Dispersion &
Suspension
3. Dispersing – What it means and what
it does
4. Dispersing Process – What makes
the TRM different?
5. Parameters Controlling the TRM
dispersing process
3. 3because precision matters.
› Importance of TRM dispersed suspensions in the value-added chain
INTRODUCTION – UTILIZATION OF
SUSPENSIONS
Dispersing with Three Roll Mills _ Introduction
4. 4because precision matters.
Physical
› electrical
› mechanical
› optical
› tribology
› thermal
› magnetic
› etc.
Technological
› shrinking
› quality
› plasticity
› process ability
› etc.
Chemical
› corrosion resistance
› flammability
› antimicrobial
› absorption/ adsorption
› etc.
Efficiency
› less raw material
› less energy
› less emissions
› better recycling
› etc.
DEFINING SPECIFIC MATERIAL PROPERTIES
Dispersing with Three Roll Mills
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DEFINED DISPERSION FOR SPECIFIC MARKETS
Thick film-Technology
› Electronics
› Sensors
› Precision resistors and
potentiometers
› Solder paste and flux
› Silicon based Photovoltaics
› Technical Ceramic
› Printing Inks
› Coatings
› Lubricants and Adhesives
› Chemistry
› Pharmacy
› Food
› Cosmetics
› Dental paste
› Chocolate
› Ceramic
› etc.
Printed Electronics
› Passive Components
› Organic Photovoltaics
› Batteries, Super capacitors
› Getter Material, e.g. in
OLED lighting and Displays
› EXAKT TRM – Indispensable in Laboratory, R&D and Production
Dispersing with Three Roll Mills _ Introduction
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DEFINITION: PARTICLE, AGGLOMERATE,
AGGREGATE
Particle
› In EXAKT terms we define Particle as the part of the disperse phase which shall
be separated in the dispersing process, e.g. agglomerates.
Primary Particle:
› Nanoparticles which can connect to larger aggregates or agglomerates
Secondary Particle:
› Agglomerates and Aggregates are also called secondary particles
Agglomerate
› A group of weakly bounded or physically connected primary particles or
aggregates, or a mixture of both.
Aggregate
› Very strongly bonded, melted or physically complex connected primary particles.
Dispersing with Three Roll Mills _ Introduction
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Particle
Secondary Particle
DEFINITION: PARTICLE, AGGLOMERATE,
AGGREGATE
Primary Particle
Aggregate Agglomerate
› Agglomerates are mainly separated in the TRM dispersing process
Dispersing with Three Roll Mills _ Introduction
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DEFINITION OF DISPERSION + SUSPENSION
Dispersion
› A mixture of at least 2 heterogeneous substances, which can not dissolve or
chemically bond. The disperse phase is distributed in the continuous phase.
Suspension
› A suspension is a sub-group of the dispersion. Solids (disperse phase) are
distributed in a fluid (continuous phase).
Particle sizes of the disperse phase:
› Colloidal dispersion -> Particle size 1 nm < X <1 µm
› Coarse dispersion -> Particle size > 1µm
Relevance for the TRM application:
› Mainly coarse dispersed suspensions, with an increasing importance
of colloidal dispersions in high tech nanotechnology applications
Dispersing with Three Roll Mills _ Introduction
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DISPERSING WITH TRM
What kind of suspension can be
processed with a TRM ?
› Coarse and colloidal dispersion, well pre-mixed
› Viscosity range 10^2 to 10^7 mPas (=cP)
Dispersing with Three Roll Mills _ Introduction
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WHY DISPERSION
Goal: Realize specific material properties after formulation:
› Defined particle size
› Preservation of the primary particle's properties
› Defined separation, homogenous particle distribution
› Optimized wetting
› Defined rheological properties
› Reproducibility in production process
Separate Agglomerate
› EXAKT TRM allow precise and reproducible dispersing in the required
level of fineness
Dispersing with Three Roll Mills _ Introduction
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Flow behaviour of
suspensions
INTERACTION IN DISPERSING PROCESS
Disperse Phase Continuous Phase
Particle Concentration
Particle surface
Particle shape
Viscosity / Rheology
Additives
Surface tension
Polarity
Particle size
Interaction
Dispersing with Three Roll Mills _ Introduction
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Needles
Tubes, such as carbon nanotubes (CNT)
Fibroid
Cubic
Spheroid
Irregular splintery
PRIMARY PARTICLES AND THEIR SHAPES
Plate-shaped
Globular
› With EXAKT TRM, the shape (morphology) of the primary particles is
not changed
Dispersing with Three Roll Mills _ Introduction
15. 15because precision matters.
RHEOLOGICAL PROPERTIES OF SUSPENSIONS
Shear thickening
(dilatant fluid)
Effectiveviscosity
Constant independent to shear
(Newtonian fluid)
Shear thinning
(pseudo plastic fluid)
constant shear rate
Time depending shear thinning
(thixotropic fluid)
Soaps, tar,
vegetable oil,
adhesives, inks,
peanut butter and
some slurries
Water, mineral oil,
syrup,
hydrocarbons, resin
Gels, lattices, inks,
lotions, cooking fat
Slurries, clays,
confectionaries
Shear rateTime
EffectiveviscosityEffectiveviscosity
Effectiveviscosity
Shear rateShear rate
Dispersing with Three Roll Mills _ Introduction
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WHAT IS FINENESS – EXAKT TEST KIT
Grindometer
An easy and handy way to check the particle size / fineness
Xs
EXAKT Grindometer (0- 25 / 50 /100) µm
Dispersing with Three Roll Mills _ Introduction
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EXAMPLE OF NARROW PARTICLE DISTRIBUTION
Exclusion threshold,
no oversize particles
No growth in small particles
Target size
Channel Particle size Absolute
frequency
Distribution
DiameterQuantitydistribution
Microscope / Software evaluation
e.g. Leica
Dispersing with Three Roll Mills _ Introduction
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DISPERSING PROCESS
What describes the dispersing process?
› Dispersing is a matter of energy applied over time
› Energy is applied with shear force
› The shear force is controlled and manipulated by machine characteristics
and operating parameters
Dispersing with Three Roll Mills _ Introduction
20. 20because precision matters.
SHEAR IN TRM SYSTEMS
› Friction between the rotating rollers and the suspension in the nip creates a force
on the particles
› Due to the speed difference of the two roller, the force acting on the particles
increase from the slower to the faster roller.
› Different forces acting on the same agglomerate result in separation of the
agglomerate.
1 2
Dispersing with Three Roll Mills _ Introduction
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APPLIED ENERGY
Relatively weak bonding
Separation into primary
particle is possible
Strong bonding
Separation may not
be possible, its more
like breaking. (e.g.
grinding)
Primary particleAgglomerates
F
F
What can the TRM do to particles?
Aggregates
e.g. inorganic
pigments
e.g. CNT,
organic
pigments
Nanoparticle, extremely
strong bonding. Can
only be mechanically
broken,
e.g. grinding
Required Energy
e.g. crystal sugar,
inorganic
pigments
› TRMs are mainly used to separate agglomerates
Dispersing with Three Roll Mills _ Introduction
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Properly separated particles
WHAT IS DEFINED DISPERSING / ENERGY INPUT
– defined and required function
– no or diminished function
Improperly separated
+
-
Dispersing with Three Roll Mills _ Introduction
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TO BE AVOIDED:
UNCONTROLLED ENERGY INPUT
Destruction of primary particles and their
structure = unwanted dispersion results
uncontrolled
energy input
› Unlike other dispersion processes, EXAKT TRM´s ensure defined
energy input in the dispersion process
Dispersing with Three Roll Mills _ Introduction
24. 24because precision matters.
Fineness of separation is controlled by machine parameters
and number of cycles
homogenous
separation
un-homogenous
separation
. . . . . .
. . . . . .
GOAL: HOMOGENOUS SEPARATION
Dispersing with Three Roll Mills _ Introduction
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PARTICLE DISTRIBUTIONFrequency
Before Dispersing:
Broad size distribution
After Dispersing:
Narrow, homogenous size
distribution
particle size
Frequency distribution of particles in the dispersing process
› EXAKT TRM achieves homogenous particle distribution and sizes
Dispersing with Three Roll Mills _ Introduction
26. EXAKT Technologies
7002 N. Broadway Extension
Oklahoma City, OK 73116
800-866-7172
info@exaktusa.com
www.exaktusa.com