Abstract
Microcapsules, with sodium silicate solution as core, were produced using complex coacervation in a double, oil-in-water-in oil, emulsion system. The shell material was a gelatin–acacia gum crosslinked coacervate and the produced microcapsules had diameters ranging from 300 to 700 μm. The shell material designed with switchable mechanical properties. When it is hydrated exhibits soft and ‘rubbery’ behaviour and, when dried, transitions to a stiff and ‘glassy’ material. The microcapsules survived drying and rehydrating cycles and preserved their structural integrity when exposed to highly alkaline solutions that mimic the pH environment of concrete. Microscopy revealed that the shell thickness of the microcapsules varies across their perimeter from 5 to 20 μm. Thermal analysis showed that the produced microcapsules were very stable up to 190 °C. Proof of concept investigation has demonstrated that the microcapsules successfully survive and function when exposed to a cement-based matrix. Observations showed that the microcapsules survive mixing with cement and rupture successfully upon crack formation releasing the encapsulated sodium silicate solution.
Highlights
Microencapsulation of active compounds, either solid or liquid, has gained a lot of interest in the last two decades in a wide and diverse spectrum of industries and applications
Encapsulated living cells can be protected from the immune system [1] or probiotic bacteria can be protected in microcapsules during the production of dairy products as well as during their passage through the upper intestine system [2]
Following the trends observed in other microencapsulation techniques, variation of the agitation speed of the emulsion has a profound effect on the size of the formed microcapsules
Summary
Microencapsulation of active compounds, either solid or liquid, has gained a lot of interest in the last two decades in a wide and diverse spectrum of industries and applications. Encapsulation eases handling of materials by allowing for instance liquids to be handled as solids resulting in improved manufacturing processes as in the case of the food industry [3]. Microencapsulation has been used to protect phase change and thermal energy storage materials [4] as well as to produce hollow microspheres for air-entrained concrete with increased durability [5]
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