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7 pages; International audience; 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.

International audience; Cold, binder-free tableting experiments under controlled pressure (0-450 MPa), water addition (0-10 wt.%) and pH (4, 11) were performed on powder of pyrolusite ore concentrates, refined hausmannite, bentonite, kaolinite, as well as blends of those materials. It has been shown that increased pressure was beneficial for agglomeration of oxide materials, but pressure > 250 MPa triggered an elastic recovery in the clay minerals. Water addition up to 4 wt.% improved tabletability, increasing diametral resistance and reducing elastic recovery and fines generation. Amounts above 6 wt.% decreased diametral resistance. The presence of layered-structure minerals (such as montmorillonite, kaolinite, lithiophorite) appeared to be key to determine the agglomeration potential of a sample. This study also showed that tableting provides good performances for recycling industrial manganese oxide fines by obtaining industrial-grade resistance for tablets made with an 80/20 pyrolusite concentrate/hausmannite blends and 4 wt.% H2O.

International audience; Fine particles (

12 pages; International audience; 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.

11 pages; International audience; 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.

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.

The disintegration of porous tablets, obtained by powder compression, is being studied. Tablets dissolve into a liquid through a two-step process including (i) an imbibition process inside the porous medium and (ii) a dissolution process of the powder aggregates. First, we show that the imbibition process follows the classical laws of capillarity. Then, we evidence and explain the influence of the presence of trapped gas inside the tablet. Finally, we demonstrate the existence of two limit disintegration regimes appearing at low and high porosity values.

10 pages; International audience; 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 disintegration