Networking and rheology of concentrated clay suspensions "matured" in mineral medicinal water

Authors: Aguzzi C (1) , Sánchez-Espejo R (2) , Cerezo P (1) , Machado J (3) , Bonferoni C (4) , Rossi S (4) , Salcedo I (1) , Viseras C (1,2)
(1) Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Granada (2) Andalusian Institute of Earth Sciences, CSIC-University of Granada (3) Aguas Termales de Graena (S.A.) (4) Department of Drug Sciences, University of Pavia
Source: Int J Pharm. 2013 Sep 10;453(2):473-9
DOI: 10.1016/j.ijpharm.2013.06.002 Publication date: 2013 Sep E-Publication date: June 10, 2013 Availability: abstract Copyright: © 2013 Elsevier B.V. All rights reserved.
Language: English Countries: Not specified Location: Not specified Correspondence address: Aguzzi C :


Article abstract

This work studied the influence of "maturation" conditions (time and agitation) on aggregation states, gel structure and rheological behaviour of a special kind of pharmaceutical semisolid products made of concentrated clay suspensions in mineral medicinal water. Maturation of the samples was carried out in distilled and sulphated mineral medicinal water, both in static conditions (without agitation) and with manual stirring once a week, during a maximum period of three months. At the measured pH interval (7.5-8.0), three-dimensional band-type networks resulting from face/face contacts were predominant in the laminar (disc-like) clay suspensions, whereas the fibrous (rod-like) particles formed micro-aggregates by van der Waals attractions. The high concentration of solids in the studied systems greatly determined their behaviour. Rod-like sepiolite particles tend to align the major axis in aggregates promoted by low shearing maturation, whereas aggregates of disc-like smectite particles did not have a preferential orientation and their complete swelling required long maturation time, being independent of stirring. Maturation of both kinds of suspensions resulted in improved rheological properties. Laminar clay suspensions became more structured with time, independently from static or dynamic maturation conditions, whereas for fibrous clay periodic agitation was also required. Rheological properties of the studied systems have been related to aggregation states and networking mechanisms, depending on the type of clay minerals constituents. Physical stability of the suspensions was not impaired by the specific composition of the Graena medicinal water.

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