2010-Microcapsules’ Quantification using the Streaming Potential Method

Microcapsules’ Quantification using the Streaming Potential Method

Tanja Pušić, University of Zagreb, Croatia


Modern textile finishing processes have to satisfy high demands due to the expectations of new added values, as well as durability during laundering. Research activities towards the improvement of existing materials’ performances, and the development of extraordinary functions have been intensified over the last decade.
The application of microcapsules filled with active ingredients has been adopted during the wellness finishing approach. A special feeling to the skin can be created by the slowly continuous release of natural components, providing benefits that consumers can actually feel.
Microcapsules are small particles with sizes between one and several hundred micrometers, composed of a liquid, gaseous or solid core, and a shell, which protects the contents of the core from environmental impact (pressure, heat, light, solvents, water, etc.). Depending on their purposes, shells can be permeable or impermeable.
A permeable shell makes a continuous release of the core’s contents possible. Microcapsules containing active natural ingredients, like rose, mint, aloe vera, vitamin E etc. can by applied by padding, dipping, exhausting, spraying, soaking, and screen printing procedures or during the rinsing cycle in washing machine.
Regardless of the processing phase for which they are used, it is necessary to add some components which contribute to the process quality. A binder, mostly acrylic, polyurethane, or silicone, is required, and its role is to fix microcapsules onto fabrics and hold them in place during washing.
A controlled release of the microcapsule core’s contents provides proper therapeutic and cosmetic impacts to the skin. Improvements in resistance to washing and longer lifetime
can be achieved through the selection of a proper binding agent.
The rate of active-ingredient release from a microcapsule additionally depends on fibre structure, degree of crystallinity, cross-section, and the porosity of the material. Since microcapsules are rather expensive, especially if natural ingredients are used, it is important to optimise the application, so as to obtain high resistance to various influences.
Precipitation is likely to occur in a bath, if microcapsules are used in high concentrations. It is important to note that the product functionality and durability of the applied finish depend on the applied maintenance procedures. Detergent composition, alkalinity, mechanical activity, and high temperature can cause a higher rate of microcapsule content release. Different applicable methods are possible for the characterization of functional textile materials using microcapsules.
Modifications and finishes are aimed at improving end-use properties’ impact surface charges regarding textile materials. Most textile fibres possess negative charge in neutral aqueous solutions. The zeta potential – also known as the electrokinetic potential on a material’s surface in contact with a polar medium, is governed by the dissociation of surface groups, the preferential adsorption of cations or anions, the adsorption of polyelectrolytes and surfactants, the isomorphic substitution of cations and
anions, and the accumulation or depletion of electrons.
It provides insight into the charge and adsorption characteristics of solid surfaces. The zeta potential is an experimentally-accessible parameter that can be determined using several types of electrokinetic phenomena: electro-osmosis, streaming potential, electrophoresis, and sedimentation potential.