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Dispersion Introduction with Three Roll Mills

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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.

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Dispersion Introduction with Three Roll Mills

  1. 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. 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. 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. 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
  5. 5. 5because precision matters. 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
  6. 6. 6www.exaktusa.com DEFINITION: WHAT IS DISPERSION? Dispersing with Three Roll Mills _ Introduction
  7. 7. 7because precision matters. 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
  8. 8. 8because precision matters. 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
  9. 9. 9because precision matters. 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
  10. 10. 10because precision matters. 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
  11. 11. 11www.exaktusa.com WHY DISPERSING? Dispersing with Three Roll Mills _ Introduction
  12. 12. 12because precision matters. 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
  13. 13. 13because precision matters. 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
  14. 14. 14because precision matters. 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. 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
  16. 16. 16because precision matters. 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
  17. 17. 17because precision matters. 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
  18. 18. 18www.exaktusa.com DISPERSING PROCESS Dispersing with Three Roll Mills _ Introduction
  19. 19. 19because precision matters. 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. 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
  21. 21. 21because precision matters. 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
  22. 22. 22because precision matters. 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
  23. 23. 23because precision matters. 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. 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
  25. 25. 25because precision matters. 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. 26. EXAKT Technologies 7002 N. Broadway Extension Oklahoma City, OK 73116 800-866-7172 info@exaktusa.com www.exaktusa.com

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