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Polymers 2014, 6(12), 2896-2911; doi:10.3390/polym6122896

On the Relation between Natural and Enforced Syneresis of Acidic Precipitated Silica

Institute of Thermal Process Engineering, Karlsruhe Institute of Technology (KIT), Kaiserstraße 12, 76131 Karlsruhe, Germany
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Received: 11 September 2014 / Revised: 12 November 2014 / Accepted: 19 November 2014 / Published: 26 November 2014
(This article belongs to the Special Issue Polymer Colloids)
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Abstract

Silica in industrial production processes is precipitated by mixing an acid and an inorganic precursor. In this aqueous solution, silica particles form due to a polymerization reaction and agglomeration and, finally, build a gel. Thereafter, the reaction continues, and the gel network shrinks with the expulsion of the enclosed pore liquid. This slow process is known as “natural syneresis” and strongly affects the product properties, such as the agglomerate size, specific surface or porosity of the silica produced. In order to investigate the influence of process parameters, such as temperature, pH or ionic strength, on the shrinkage in shorter time-scales, we propose an acceleration of this process and define it as “enforced syneresis”. The acceleration is performed by applying a mechanical external force to the gel by means of a plunger and measuring the shrinkage behavior under these conditions. Thereby, the conceptual idea is the prediction of the shrinkage due to natural syneresis based on the results of enforced syneresis. We are now able to predict the natural syneresis behavior from enforced syneresis data by the development of a correlative model. Using this prediction model, we can show the influence of temperature on the maximum shrinkage and on its rate in a significantly shorter time of about 12 h instead of several days. View Full-Text
Keywords: precipitation; silica; syneresis; natural; enforced; shrinkage; prediction model precipitation; silica; syneresis; natural; enforced; shrinkage; prediction model
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Wilhelm, S.; Kind, M. On the Relation between Natural and Enforced Syneresis of Acidic Precipitated Silica. Polymers 2014, 6, 2896-2911.

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