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Published byRalf Powell Modified over 9 years ago
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“Continuous” Emulsifier-Free Emulsion Polymerization
Brian Edwards McMaster University, Department of Chemistry
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Contents Introduction Equipment/Polymerization
Particle Growth Mechanism CEFEP Vs. Multistage Seeding Conclusions
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Introduction Simple alternative for the production of mono-disperse polymeric particles in a wider range of sizes Larger size mono-disperse particles have been produced by a multistage seeding process, however this is: Tedious Difficult to control
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Polymerization - Equipment
Monomer tank Water tank Reactor Condenser N2 continuously bubbled through system
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PS/2% DVB - CEFEP A nm at 1.5 h B nm at 6 h
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PS/2% DVB – Batch/CEFEP 630 nm at 5 h B m at 14 h
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PMMA/3 mol % EGDMA – Batch/CEFEP
A.758 nm at 4.5 h B.1.3 m at 5.5 h
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CEFEP Amount and timing of initiator is significant
Rate of polymerization & particle size determined by monomer feed rate Low initiator concentrations function well
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CEFEP – Contributions To Polydispersity
Later addition of initiator Excessive initiator Increase in polymerization temperature
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CEFEP Therefore: Polymerization rate and initiator concentration should be monitored Add initiator only when a significant decrease in these variables
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Mechanism of Particle Growth
Oligomeric free radicals: May terminate - in situ surfactants May grow – particle precursors & decrease in situ surfactant concentration
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Mechanism of Particle Growth
CEFEP continues with a core-shell growth mechanism Monomer feed rate is slow Polymerization occurs in outer shell
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Multistage Seeding Process
First stage B. Second stage
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Multistage Seeding Process
Third Stage B. Fourth Stage
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Multistage Vs. CEFEP Smaller particle size (Direct CEFEP)
Larger particle size, however Preparation of seed lattice – multistage Consideration of seed particle concentration – hard to control later in reaction Phase separation Secondary nucleation Smaller particle size (Direct CEFEP) After particle nucleation, just add monomer Need to consider monomer and initiator feed rates/amounts
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Conclusions Simple Preliminary batch polymerization can produce quite large particles Spherical particles with uniform cross-linking Monodispersity is achieved – simply maintain temperature and monomer/initiator amounts/feed rate
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References Li, J.Q. and Salovey, R. J Polym Sci Part A: Polym Chem 2000, 38, 318. Zou, D., Ma, S., Guan, R., Park, M., Sun, L., Aklonis, J.J. and Salovey, R. J Polym Sci Part A: Polym Chem 1992, 30, 137. Zou, D., Sun, L. and Aklonis, J.J. J Polym Sci Part A: Polym Chem 1992, 30, 1463.
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References 4. O’Callaghan, K.J., Paine, A.J. and Rudin, A. J Appl Polym Sci 1995, 58, 2047. 5. Kim, J.H., Chainey, M., El-Aasser, M.S. and Vanderhoff, J.W. J Polym Sci Part A: Polym Chem 1992, 30, 171. 6. O’Callaghan, K.J., Paine, A.J. and Rudin, A. J Polym Sci Part A: Polym Chem 1995, 33, 1849.
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