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Microencapsulation in polyurea shell: Kinetics and film structure

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Field Value
 
Title Microencapsulation in polyurea shell: Kinetics and film structure
 
Creator YADAV, SK
KHILAR, KC
SURESH, AK
 
Subject interfacial polycondensation
polymerization
 
Description Interfacial polycondensation is an important polymerization technique that encapsulates a variety of active principles. Mechanisms governing the reaction and interplay of physical and chemical rate processes need to be understood for both rational design of reaction equipment and the process control to produce capsules with desired characteristics. A theoretical and experimental study of the process is reported here. Kinetic data were obtained over a range of concentrations, monomer mole ratios and polymer film thicknesses, using a technique that relies on the on-line measurement of pH as a function of time. To understand the mechanisms the reaction was slowed down by reducing the interfacial area. A minimum thickness of the polymer was observed to be necessary so that capsules preserve their integrity and do not break up. The theoretical model developed considers ionic equilibria in the aqueous phase and the resistances due to external mass transfer, diffusion through the polymer, and interfacial reaction. Under the conditions chosen, the resistance due to the chemical reaction is generally more dominant. Values of rate parameters were determined by fitting the model to the experimental data. Observed variations in the diffusivity between different experiments were rationalized through a study of the crystalline structure of polymers.
 
Publisher AMER INST CHEMICAL ENGINEERS
 
Date 2011-07-15T11:36:21Z
2011-12-26T12:49:28Z
2011-12-27T05:51:30Z
2011-07-15T11:36:21Z
2011-12-26T12:49:28Z
2011-12-27T05:51:30Z
1996
 
Type Article
 
Identifier AICHE JOURNAL, 42(9), 2616-2626
0001-1541
http://dx.doi.org/10.1002/aic.690420922
http://dspace.library.iitb.ac.in/xmlui/handle/10054/4260
http://hdl.handle.net/10054/4260
 
Language en