From compressibility to structural investigation of sodium dodecyl sulphate — Part 1: Powder and tablet physico-chemical characteristics

As a part of a study on detergent tablets, investigations were carried out to elucidate the compression behavior of a powdered surfactant, sodium dodecyl sulphate (SDS), based on a comparison with the main component of the formulation, i.e. the chorine provider (DCCNa). The compacted SDS exhibited poor cohesion as well as delayed dissolution whatever the compression pressure. The microscopic observations and the mercury porosimetry measurements both demonstrated that a residual porosity existed in the tablets but the dissolution times were always long. A modification of SDS in contact with water, forming a structure like a gel, probably occurred, inducing the closing of the pores and thereby limiting the water intrusion into the tablets

Deep reflection seismic imaging of the internal zone of the South Armorican Hercynian belt (western France) (ARMOR 2/Géofrance 3D Program) Imagerie sismique de la zone interne de la chaîne hercynienne sud-armoricaine (projet Armor 2/programme Géofrance 3D)

International audienceWe present results and interpretation of a 72 km long deep seismic reflection profile acquired across the internal zone of the Hercynian belt of South Brittany. The profile is of excellent quality, most of the crust being highly reflective. The “ARMOR 2 South” profile, is correlated with the “ARMOR 2 North” profile that was published in 2003. Correlation of the main subsurface reflections with surface geological and structural data provides important information about the crustal structure that resulted from thickening during Late Devonian and regional-scale extension during Late Carboniferous. In particular, seismics image shows a very high reflectivity zone, lying flat over more than 40 km at about 10–12 km depth. This zone is interpreted as a major zone of ductile crustal thinning. Nous présentons les résultats et l'interprétation d'un profil de sismique réflexion en écoute longue, de 72 km de long à travers les zones internes de la chaîne hercynienne sud-armoricaine. Le profil est d'excellente qualité, avec une forte réflectivité à travers toute la croûte. Le profil, « ARMOR 2 Sud », est corrélé avec le profil « ARMOR 2 Nord » publié en 2003. Les corrélations des réflexions les plus superficielles avec les données géologiques et structurales de surface fournissent d'importantes informations sur la structure crustale qui résulte d'un épaississement débutant au Dévonien supérieur et d'une extension régionale au Carbonifère supérieur. En particulier, la sismique met en évidence une zone sub-horizontale à très forte réflectivité, de plus de 40 km de long à environ 10–12 km de profondeur. Cette zone est interprétée comme une zone d'amincissement crustal majeur

From compressibility to structural investigation of sodium dodecyl sulphate — Part 2: A singular behavior under pressure

Investigations were carried out to elucidate the compression behavior of a powdered surfactant, sodium dodecyl sulphate (SDS), based on a comparison with the main component of a detergent formulation, i.e. the chorine provider (DCCNa). The energetic analysis based on the compression cycles highlighted a lower compressibility of SDS compared with DCCNa, especially due to its worse packing ability, larger elasticity and bad cohesion ability. Also, it pointed out that the pycnometric density seemed to be overrun under pressure whereas a residual porosity had been evidenced in the expanded tablets. DSC/DTA analysis, Raman spectroscopy as well as powder X-ray diffraction refuted the hypothesis of a physico-chemical transformation of SDS under pressure. This was in accordance with the morphology of the SDS particles, quite unchanged after compression. The pycnometric density measurements have been improved; firstly, it allowed to properly express the compaction ratio of the ejected SDS tablets, and secondly, it led to conclude to a reversible intrinsic compressibility for pressures higher than 50 MPa, explained by the predominant elastic behavior of SDS

Characterization of porous textures in order to explain the influence of a surfactant on the end-use properties of detergent tablets

The functional characteristics (mechanical strength, disintegration and dissolution times) of effervescent detergent tablets containing chlorine provider were investigated according to the presence of a surfactant, sodium dodecyl sulphate (SDS). Tablets were compared for similar total porosity. The end-use property study highlighted that the presence of 2% of sodium dodecyl sulphate was not favorable to the tablet mechanical characteristics, inducing a lower ''bonding ability''. The linear relationship between the disintegration and dissolution times showed that the disintegration time was relevant to express the behavior of the tablets in water. The disintegration data showed two zones: when porosity was higher than 20%, the disintegration time was always lower than 2 min g-1 and similar for both formulas; for lower porosities, the disintegration time increased and was higher in the presence of the surfactant. In this second case, the released CO2 due to the reaction between adipic acid and sodium bicarbonate in water was slowed down in the presence of the surfactant, confirming the disintegration data. However, this negative effect of SDS on the disintegration time could not be linked to a difference of pore size distribution between the two formulas. So, despite the creation of weak interparticle bonds with the other compounds of the formula, the presence of SDS increased the disintegration by limiting the water uptake, independently of the porous texture. Moreover, no preferential localization of the surfactant at the surface of the tablet might be involved to explain the effect of SDS on the tablet accessibility by water

Parametric Study of Surfactant Effect on Mechanical and Dissolution Properties of Detergent Tablets

The aim of this study os to investigate the functional characteristics (mechanical strength and disintegration time) of effervescent detergent tablets containing chlorine provider in the presence of surfactant. A preliminary study high-lighted that the presence of 2% of sodiumdodecyl sulfate (SDS) was not favorable to the tablet mechanical properties, inducing a lower "bonding ability, whereas the disintegration time and the end-dissolution time led us to consider just the disintegration time to express the behavior of the tablets in water. A parametric study has been completed to assess the influence of the mixing method, the nature, the hydrophilic-lipophilic balance, the granulometry, and the cçoncentration of the surfactant on the tablet properties. In all cases, surfactant presented adverse effects on the mechanical properties and had a retarding effect on disintegration time, but neither solubility, hydrophilic-lipophilic balance, interfacial properties, nor ionic character could be clearly involved to explain surfactant contribution. Furthermore, tablet dissolution could not be correlated to surfactant available surface, as evidenced by granulometry comparison on one side and concentration impact on the other side (a similar effect was observed from 1 to 15%). On the contrary, mechanical properties were dramaged as much as the area developed by surfactant particles increased. On the basis of this work, it has been concluded that SDS interacts with the other compounds of the formula by creating weak interparticle bond and limiting water uptake responsable for disintegratio

Dissolution of a surfactant-containing active porous material

We have studied the imbibition and dissolution of a porous material in two separate scenarios: (1) when the porous material contains a surfactant powder and (2) when the porous material is dissolved in a surfactant solution. We show that the dissolution kinetics in both scenarios is significantly affected by the presence of the surfactant and results in an increase in the characteristic imbibition time of the porous material, which can be well understood in the framework of the classical law of capillarity. Slowing of the imbibition kinetics was found to be affected by a modification of the liquid wetting properties, but is also affected by a variation in the solubility of the porous material in the presence of the surfactant. Furthermore, there is a depletion effect of the surfactant inside the rising liquid, which is in good agreement with previous work and theoretical predictions

La constitution des autorités numériques dans la production et la circulation de l’information

Ce dossier ouvre la complexité de la notion d’autorité aux sciences de l’information et de la communication. Ce concept est utilisépar notre discipline, essentiellementpour étudierl'accès et le partage de l'information, l’organisation des connaissances, la communication organisationnelle et les travaux sur l’e-réputation. Les travaux sélectionnés et publiés dans ce numéro remettent en perspective les liens entre légitimité et autorité, reconnaissance et signatures énonciatives, visibilité et réputation à l’heure des plateformes du web. Les terrains d’investigation représentés se situent dans la communication culturelle, politique et médiatique ainsi que dans celui du document numérique