title: Networking and rheology of concentrated clay suspensions "matured" in mineral medicinal water.
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.
authors.affiliation: Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Granada, Campus of Cartuja, s/n, 18071 Granada, Spain. carola@ugr.es
authors.forename: Carola
authors.initials: C
authors.lastname: Aguzzi
authors.forename: Rita
authors.initials: R
authors.lastname: Sánchez-Espejo
authors.forename: Pilar
authors.initials: P
authors.lastname: Cerezo
authors.forename: José
authors.initials: J
authors.lastname: Machado
authors.forename: Cristina
authors.initials: C
authors.lastname: Bonferoni
authors.forename: Silvia
authors.initials: S
authors.lastname: Rossi
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Salcedo
authors.forename: César
authors.initials: C
authors.lastname: Viseras
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D000538:Aluminum Silicates; D000077215:Clay; D006863:Hydrogen-Ion Concentration; D017616:Magnesium Compounds / Q000737:chemistry*; D017633:Magnesium Silicates / Q000737:chemistry*; D008900:Mineral Waters; D010316:Particle Size; D012212:Rheology; D017640:Silicates / Q000737:chemistry*; D013535:Suspensions; D014783:Viscosity; D014867:Water / Q000032:analysis
chemical_list: D017607:Aluminum Compounds; D000538:Aluminum Silicates; D017616:Magnesium Compounds; D017633:Magnesium Silicates; D008900:Mineral Waters; D017640:Silicates; D013535:Suspensions; D014867:Water; C033065:aluminum magnesium silicate; C001671:magnesium trisilicate; D000077215:Clay
keywords: Clay pastes; Maturation; Mineral medicinal water; Pelotherapy; Rheology