1. Dispersion In Air of Micron and Nanometer Sized Particulate Systems: PREDICTING AGGLOMERATE STRENGTH N. Stevens H. El-Shall*, K. Powers*, A. Ranade**, and Y. Rabinovich* *University of Florida ** Particle Systems, LLC Center for Particulate & Surfactant Systems (CPaSS) IAB Meeting University of Columbia, New York, NY August 20, 2009

2. l Agglomeration is responsible for w Dosing errors for inhaled drugs w Defects in powder coatings w Formulation errors w Bulk transfer powder hang-up w Decreased effectiveness of products w Poor performance obscurants Dispersion is important to: Health, Industry, Environment, Defense and Emerging Areas: Industrial Relevance Bottom Line: Improper dispersion will impact cost and quality

3. Agglomeration and Powder Processing Specific Objectives: develop a methodology/protocol to predict the dispersability of powders based on agglomerate strength measurements State of the Art: ad-hoc approach, using brute force, wastes energy Powder Drying Dispersion Powder production Powder processing Final Product Wet Dry bottle neck

4. Develop Develop relationship between agglomerate strength, interparticle forces, and dispersion for more energy and material efficient processes & equipment design l l Shear Strength– Aerodisperser, Sonic nozzle, and/ or Calibrated ultrasonic technique* l l Interparticle Forces – AFM l l Particle Morphology, fracture surfaces, neck characterization- SEM, TEM, Image analysis Develop Develop a model using a Design of Experiments l l Used successfully for modeling dispersion of IR Obscurants Research Approach * “ * “Determination of agglomerate strength distributions : Part 1. Calibration via ultrasonic forces” by S. G. Thoma, M. Ciftcioglu and D. M. Smith, Powder Technology Volume 68, Issue 1, October 1991, Pages 53-61Powder Technology Volume 68, Issue 1

5. Effect of Drying Technique on Agglomerate Strength Drying MethodMean (µm)Agglomeration (%) Primary Particle Size (Al) 10- SC-CO 2 1785% Sublime Dry5188% Freeze Dry15896% Convection Dry34498% Almost every technique results in agglomeration Do agglomerates have different strengths? What is the best way to characterize this?

6. Agglomerate Strength Characterization Dry Aerosol System: Aerosizer or Sonic Nozzle Agglomerate strength monitored w.r.t. shearing force Agglomerate strength monitored w.r.t. shearing force Control over shearing force Control over shearing force Broad range of nozzle designs Broad range of nozzle designs Monitor changes in PSD with laser diffraction Monitor changes in PSD with laser diffraction Monitor whole PSD or size of interest Monitor whole PSD or size of interest

7. Methodology Calibrate Agglomerate Strength Analyse Report Glass Ballotini: Known breaking strength Used to calibrate shear force of nozzle Test Powders: Model - alumina Industrial powders Agglomerate Strength Distributions: Quantitative d50 and PSD vs. shear force

8. Hypothesis Supercritical Drying Evaporation MODEL FOR DEAGGLOMERATION Use model to develop energy & material efficient processes & equipment Long term goal: model deagglomeration from first principles Evaporative Drying Super Critical Drying

9. Outcomes/ Deliverables Agglomerate strength measuring technique and protocol Effect of processing methods on agglomerate strength Correlation between of interparticle forces and agglomerate strength A model to correlate powder dispersion in air to powder characteristics and dispersion techniques The authors acknowledge the financial support of CPaSS, the National Science Foundation (NSF), and the CPaSS Industrial Partners. Acknowledgements