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Structure-property relationship of dispersants used in ceramic - - PowerPoint PPT Presentation

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Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Structure-property relationship of dispersants used in ceramic feedstock development Thomas Hanemann, Richard Heldele, Jrgen Hauelt Forschungszentrum Karlsruhe, Institute for

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Forschungszentrum Karlsruhe

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Structure-property relationship of dispersants used in ceramic feedstock development

Thomas Hanemann, Richard Heldele, Jürgen Haußelt

Forschungszentrum Karlsruhe, Institute for Materials Research III Albert-Ludwigs-University Freiburg, Department of Microsystems Engineering

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The Alchemist, Joseph Wright of Derby 1771

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Outline

  • Relevanve to
  • Introduction powder injection molding
  • Organic interface tailoring
  • Structure-property relationships
  • Consequences for powder injection molding
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The aim of the µSAPIENT CA is to prepare the European industry for a move from designing MST-based products for specific materials and technologies (platform and technology push products) to adopting new disruptive processes/process chains to satisfy specific functional and technical requirements of new emerging multi-material products:

  • creation of meso/micro-products that are less process intensive
  • broadening of product capabilities
  • better exploitation of the application potential of new generic

MNT by European companies

  • facilitating a new level of synergetic integration of micro- &

nano- manufacturing technologies in support of a number of European industrial sectors

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Micro Powder Injection Molding

  • exploits established plastic micro replication technology

for the realization of ceramic and metal microparts

  • huge potential for automation
  • low cost fabrication method for ceramic and metalic

microparts

  • technology close to industry
  • but: molding is only a part of a complex process chain
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  • 1. High pressure injection molding:

Mass production

  • 2. Low pressure injection molding:

Small scale series production Rapid Prototyping

  • 3. Composite reaction injection molding:

Rapid Protyping Materials testing like additive screening a.o.

Micro Powder Injection Molding - Variants

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Micro Powder Injection Molding - Process Chain

  • 1. Ceramic filler conditioning
  • 2. Feedstock preparation
  • 3. Replication/Molding
  • 4. Debinding
  • 5. Sintering
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Micro Powder Injection Molding - Process Chain

  • 1. Ceramic filler conditioning
  • 2. Feedstock preparation
  • 3. Replication/Molding
  • 4. Debinding
  • 5. Sintering
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  • 1. Agglomeration/Deagglomeration

(depending on particle size and specific surface area)

  • milling
  • sonication
  • 2. Milling (particle shape modification)
  • 3. Drying (water removal)
  • 4. Formation of multimodal mixtures (load improvement)
  • 5. Surface modification (load improvement, homogenization)

Ceramic Filler Conditioning

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  • 1. Agglomeration/Deagglomeration

(depending on particle size and specific surface area)

  • milling
  • sonication
  • 2. Milling (particle shape modification)
  • 3. Drying (water removal)
  • 4. Formation of multimodal mixtures (load improvement)
  • 5. Surface modification (load improvement, homogenization)

Ceramic Filler Conditioning

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  • 1. High pressure injection molding:

Binder composition: thermoplastics, wax, additives Compounding temperature: 150-180° C Viscosity: 100-500 1/s

  • 2. Low pressure injection molding:

Binder composition: wax, additives Compounding temperature: 70-90° C Viscosity: 2-20 1/s

  • 3. Composite reaction injection molding:

Binder composition: reactive resins, additives Compounding temperature: 25° C Viscosity: 0.1-10 1/s

Polymer-based Feedstocks - Composition

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Polymer-based Feedstocks - Interfaces

  • Compatibilization of hydrophilic and hydrophobic environment
  • Reduction of the particle-particle interaction
  • Reduction of the feedstocks viscosity

but: multifunctional dispersants tend to network formation

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Polymer-based Feedstocks - Interfaces

15 - 20 Solubility improver 13 - 15 Detergents 8 - 18 Emulsifier (oil in water) 7 - 9 Wetting agent/dispersant 3 - 6 Emulsifier (water in oil) 1 - 3 Defoamer

HLB-Value Function nonpolar systems polar systems

) 1 ( 20

total ic hydrophoph

M M HLB − ∗ =

Hydrophilic-lipophilic-balance value

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Interface - Polyethylene-glycol-alkylether Brij-Dispergants

Nomenclature: Brij5x (x: 2, 6, 8): hydrophobic saturated C16-moiety HLB-value Brij52: 2 hydrophilic glycol-units 5.3 Brij56: 10 hydrophilic glycol-units 12.9 Brij58: 20 hydrophilic glycol-units 15.7 Brij7x (x: 2, 6, 8): hydrophobic saturated C18-moiety Brij9x (x: 2, 7, 8): hydrophobic unsaturated C18-moiety hydrophilic hydrophobic

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Interface - Citrates

  • Citrates: 4 potential coupling positions (HLB: 6.2 – 8.1)
  • TEC, TBC: free hydroxy functionality (dipole moment ≈ 3.7 - 4.5)
  • ATEC, ATBC: covered hydroxy functionality (dipole moment ≈ 1.4 - 1.5)

pronounced network formation capability

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  • 1. Reactive resin based feedstock

Alumina filler: average particle size: 0.7 µm, specific surface area: 6-8 m²/g unsaturated polyester resin: dipole moment ≠ 0, rel. permittivity ≈ 3.0 reference feedstock: 50 wt% polyester resin 50 wt% (22.4 vol%) alumina

  • 2. Thermoplastic feedstock

Zirconia filler: average particle size: 0.45 µm, specific surface area: 6 m²/g polyethylene/wax binder: dipole moment = 0, rel. permittivity ≈ 2.3 reference feedstock: 50 vol% binder 50 vol% zirconia

Polymer-based Feedstocks - Systems

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Reactive resin based feedstocks

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Rheology - Influence of Dispersants

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Rheology - Influence of Dispersants

Brij98 Brij52 Viscosity reduction around 15-20% can be achieved using:

  • Brij52, Brij72, Brij92

small HLB-value i.e. short polar moiety Neglible effect occurs or viscosity increase using:

  • Brij58, Brij78, Brij98

large HLB-value i.e. long polar moiety

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Rheology - Influence of Dispersant Concentration

Viscosity reduction increases with increasing Brij52, Brij72, Brij92 amount 20° C 60° C

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8.2 8.3 9.1 8.1 8.2 8.9 8.1 8.2 8.9

  • Spec. surface

(m²/mg) 15 15.6 1.5 9.7 1150 Brij98 12 9.8 0.9 5.6 709 Brij97 4.9 5.4 0.9 2.9 357 Brij92 15 15.5 1.5 9.7 1152 Brij78 12 9.7 0.9 5.9 711 Brij76 4.9 5.3 0.9 3.1 359 Brij72 15.7 15.2 1.5 9.4 1124 Brij58 12.9 9.3 0.9 5.7 683 Brij56 5.3 4.9 0.9 2.9 330 Brij52 HLB value Surface (nm²) Dipole- moment (D) Length (nm)

  • Mol. weight

(g/mole)

Dispersant Physical Specifications

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8.2 8.3 9.1 8.1 8.2 8.9 8.1 8.2 8.9

  • Spec. surface

(m²/mg) 15 15.6 1.5 9.7 1150 Brij98 12 9.8 0.9 5.6 709 Brij97 4.9 5.4 0.9 2.9 357 Brij92 15 15.5 1.5 9.7 1152 Brij78 12 9.7 0.9 5.9 711 Brij76 4.9 5.3 0.9 3.1 359 Brij72 15.7 15.2 1.5 9.4 1124 Brij58 12.9 9.3 0.9 5.7 683 Brij56 5.3 4.9 0.9 2.9 330 Brij52 HLB value Surface (nm²) Dipole- moment (D) Length (nm)

  • Mol. weight

(g/mole)

Dispersant Physical Specifications

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Rheology - Influence of Dispersants

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Rheology - Influence of Dispersants

ATBC

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Rheology - Influence of Dispersant Concentration

Viscosity reduction around 20% can be achieved using:

  • 2 wt% ATBC or TEC

neglible effect occurs using:

  • ATEC or TBC

correlation with molecular properties difficult interaction with polymer ? 20° C 60° C

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Thermoplastic based feedstocks

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Torque measurement - Influence of Dispersants

  • Variation of dispersant
  • T = 125°

C, ω = 30rpm difference between Brij 52 and Brij 98:

  • smaller size
  • lower dipole moment
  • lower HLB-value

rapid wetting

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Torque measurement - Influence of Dispersants

  • Variation of dispersant
  • T = 125°

C, ω = 30rpm polar TEC, TBC: strong network formation non-polar ATBC, ATEC: weak network formation due to incompatibility with PE

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  • Addition of dispersants affects feedstock viscosity significantly
  • Dispersant concentration has to be optimized individually
  • Influence prediction is possible if
  • dispersant chemistry
  • fillers surface chemistry
  • binder composition

are known

Consequences for powder injection molding

Inorganic filler Polymer binder system Interface