A1261850408tHcqZ - PowerPoint PPT Presentation

Title: A1261850408tHcqZ


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IMPLICATIONS OF AGGREGATION AND MASS FRACTAL
NATURE OF AGGREGATES ON THE PROPERTIES OF ORGANIC
PIGMENTS AND POLYMER COMPOSITES By N. Agashe,
G. Beaucage, D. Kohls, S. Sukumaran, G.
Skillas, G. Long, J. Ilavsky, P. Jemian, L.
Clapp, R. Schwartz Department of Materials
Science and Engineering, University of
Cincinnati, Cincinnati, OH 45220, USA Inst. f.
Verfahrenstechnik, ETH Zentrum ML F24, CH8092
Zurich, Switzerland. Ceramics Division NIST,
Gaithersburg, MD 20899, USA. University of
Maryland, College Park, MD 20742,
USA. University of Illinois at UrbanaChampaign,
IL 61801 , USA. Colors Group, Sun Chemical
Corp., Cincinnati, OH 45232 , USA.
Monoazo Pigment Red 122

• What are Pigments ??
• Most Common types of Pigments are,
• Inorganic Pigments
• Organic Pigments
• Other types include Metallic and Pearlescent.

TEM Dpp 0.1 mm (length) LS Dagg 0.2 mm
Powder Non Mass Fractal Dpp 0.13 mm 1 in
PP Mass Fractal, df 1.91 (DLA) Dpp 0.13
mm 5 in PP Mass Fractal, df 1.5 (DLA) Dpp
0.13 mm
The smallest size of an aggregate necessary for
scattering is given by Braggs Law,

• Regimes of Aggregation
• Diffusion Limited Aggregation, df lt 2 (df 1.8)
• Reaction Limited Aggregation, df gt 2 (df 2.5)
• Intermediate Regime

• Results
• The results are a survey of some of the behavior
  seen when organic pigments are milled into
  polymers.
• This is the first attempt to characterize the
  aggregation according to the process by which the
  aggregates are formed.
• The mass fractal behavior of these aggregates is
  studied.
• The primary particle of each organic pigment is
  examined to see if it is made up of a single
  crystal or multi crystals.

The optimum size of the aggregate can be
estimated by integrating the Guinier Law,
Monoazo Pigment Violet 19

• Why Organic Pigments ?
• Most of the research in the pigment industry is
  concentrated on inorganic pigments like titania.
• Until now all work on organic pigments has
  examined only the surface fractal nature of the
  organic pigment particles.
• We make the first attempt to study the
  aggregation of organic pigments, the mass fractal
  nature of these aggregates and their relationship
  to the optical properties.
• The typical size of primary particles of organic
  pigments is 0.05 to 0.1 mm. The optimal size
  necessary for good scattering is about 0.5 mm.

Diazo Pigment Red 170 (235-0170)
TEM Dpp 0.05 mm LS Dagg 0.4 mm

• Aggregation of Organic Pigments
• Forces behind aggregation of organic pigments
  are weak electrostatic forces like van Der Waals
  forces, static charge, chemical polarity and
  surface tension.
• Processing also dictates the nature of the
  aggregates.
• Color is produced in pigments by scattering.

Powder Mass Fractal, df 2.32 (RLA) Dpp
0.03 mm, Dagg 1.2 mm 1 in PP Mass Fractal,
df 1.55 (DLA) Dpp 0.16 mm, Dagg 1.0 mm
5 in PP Mass Fractal, df 1 (DLA) Dpp
0.26 mm

• Fractal Structures have Fractional Dimension
• Surface Fractal Object, (ds)
• Irregular Surface
• Mass Fractal Object, (df)
• Irregular Structure

TEM Dpp 0.2 mm LS Dagg 0.4 mm
Disazo Pigment Yellow 13
Powder Non Mass Fractal Dpp 0.2 mm 20 in
PMMA Mass Fractal, df 2.5 (RLA) Dagg
2.35 mm
For visible light, l 0.5 mm

• The typical particle size for organic pigments
  is 0.05 to 0.1 mm. Aggregation is necessary for
  good scattering.

Scattering in Organic Pigments
Diazo Pigment Red 170 (235-1170) Higher
Luminosity
TEM Dpp 0.1 mm LS Dagg 0.5 mm
Mie Scattering Dilute Systems, Large Particles,
Higher Index Difference
Rayleigh Ganz Approximation All Systems, All
Particles Particles, Lower Index Difference
Powder Mass Fractal, df 2.34 (RLA) Dpp
0.035 mm, Dagg 0.32 mm 5 in PP Mass Fractal,
df 2.7 (RLA) Dpp 0.052 mm, Dagg 0.49 mm

• Common Organic Pigments are,
• Azo Pigments Monoazo (-NH-) or Diazo (-NN-)
• Quinacridones, Naphthol Reds, Diarylides,
  Rhodamines, and Naphthoic Acid.
• Phthalocyanines (Naphthol) (-CN)
• Metal and Non-metal
• Perylenes
• Carbazoles
• Triphenyl Methane
• Anthraquinone and Indigoid Pigments
• Denotation C.I. PR 122 (Pigment Red 122)

TEM Dpp 0.15 mm LS Dagg 0.35 mm
Conclusions
Powder Non Mass Fractal Dpp 0.156 mm 20
in PMMA Mass Fractal, df 2.67 (RLA) Dagg
2.01 mm
For X-Rays, the comparable contrast difference is
very small between the pigment and the polymer.

• Organic pigments field has ignored the
  importance of aggregates to optical properties.
  Mass fractal aggregates were observed for all the
  pigments when milled into polymers.
• The size of a crystal is too small to scatter
  visible light. Aggregation is critical to have
  good optical properties, and this issue has been
  dealt with for the first time.
• There is an incredible range of behavior in
  terms of aggregation, based on the polarity of
  the compound and the particle size.
• Some contradictions in the behavior can be seen.
• There is a potential to control and design the
  aggregate size and structure of organic pigments
  if we had a bit more understanding.

• PMMA, used earlier, is a non-crystalline
  polymer.
• PP is a semi-crystalline polymer. The addition
  of pigments has an effect on the crystallinity of
  PP.

• Unified Function for Mass Fractal Model
• Unified Function, used to fit the scattering
  data, is based on six parameters,
• Guinier Prefactors G1 and G2
• Radius of Gyration Rg1 and Rg2
• Power law Prefactor B1
• Fractal Dimension df

Small and Ultra Small Angle X-Ray Scattering
(SAXS/USAXS) Range of q for SAXS is 0.01 to 0.1,
while USAXS can go down to q value of 0.0001
The diameter of a sphere having similar Rg as the
aggregate can be used to estimate the size of the
aggregate.
Acknowledgements The UNICAT facility at the
Advanced Photon Source (APS) is supported by the
Univ of Illinois at Urbana-Champaign, Materials
Research Laboratory (U.S. DOE, the State of
Illinois-IBHE-HECA, and the NSF), the Oak Ridge
National Laboratory (U.S. DOE under contract with
UT-Battelle LLC), the National Institute of
Standards and Technology (U.S. Department of
Commerce) and UOP LLC. The APS is supported by
the U.S. DOE, Basic Energy Sciences, Office of
Science under contract No. W-31-109-ENG-38.