Factors affecting the morphology of microcapsules produced via a complex coacervation process, an experimental study

Autori: V. Guida, C. Ricci
Presentato al: VIII Convegno Nazionale di Reologia
Anno: 2004
Volume: Unico
Issue: Unico
Casa Editrice:
Lingua: English


Abstract
Complex coacervation is a process that allows producing soft
liquid core microcapsules starting from oil in water emulsion.
Carbonless copy paper as well as scratch and sniff perfume samples are
made using microcapsules produced by coacervation technology.
The properties of the microcapsules produced, their size distribution
and their morphology are greatly influenced from the emulsion
properties and the fluidodynamics of the emulsification process. This
work analyses experimentally a specific complex coacervation system.
As a first step, the system thermodynamics is characterized in order
to study the coacervation equilibrium. Then, encapsulation yield,
kinetics and results are experimentally characterized using a DoE
technique.
In a second stage, it has been examined the influence of fluidodynamics
on capsules size distribution. Experimental results are compared
with the prediction of theoretical models.
The key results of this work are summarized below:
• By changing the formulation of the emulsion, it is possible to
control microcapsules physical properties, such as mechanical resistance.
• By controlling the rheology of the emulsion and the emulsification
process, it is possible to control microcapsules size distribution.
• Preliminary data indicate that the kinetics of the process is controlled
by the diffusion of cross linking agent in the coacervate gel.
• The use of conventional emulsification route seems to pose a
limit to minimum size of microcapsules achievable, as increasing agitation
speed the encapsulation yield is reduced and coacervate microparticles
are formed.


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