In this study, powder flowability is assessed during granular compaction under free surface conditions by using Hausner ratio (HR) as flowability index. Different kinds of pharmaceutical and food powders were examined. The assessment of the flow properties of these powders according to HR is obtained using three compaction devices: DensiTap (R), GranuPack (R) and a homemade Vibratory device (particle dumper). The comparison of the HR values obtained with each compaction test provided a deeper understanding of HR. Here we show that HR is strongly dependent on the energy supplied to the system. This energy is the result of the vibration wave transmitted to the powder bed, and is strongly dependent on the vibration amplitude, i.e. on the device used. HR analysis as a function of the energy supplied to the powder bed allowed us to determine a maximal HR value, denoted ultimate HR (HRU), obtained when reaching a maximal compaction state. Thus, a new approach is proposed to determine flow behavior, through HR, as a function of the energy supplied to the powder bed. (C) 2019 Elsevier B.V. All rights reserved.

In the present work, concentrated Oil-in-Water (O/W) emulsions were stabilized using egg albumen protein isolate as the only emulsifier. A helicoidal geometry was used and compared with a conventional one to assure an optimal emulsion preparation with that unusual geometry in order to come up with the utility of this rheometer as a valuable tool for understanding and controlling the emulsification process. The results put forward the importance of controlling the emulsification process to optimize the properties of the final emulsion and demonstrating a good agreement between in situ and off-line measurements obtained in mixer-type and conventional rheometers, respectively. Flow properties of the different emulsion prepared were measured, showing an increase in the viscosity with the agitation speed (from 10 to 16 to 114-117 Pa s), protein concentration (from 30 to 40 to 106-125 Pa s) and oil concentration (from 15 to 20 to 130-180 Pa s). Furthermore, the droplet size distribution (DSD) was also measured obtaining the influence of the different parameters with the Sauter diameter (a decrease from 20 to 30 to 7-8 mu m, from 26 to 3 mu m and from 17 to 24 to 8-14 mu m was observed by increasing the agitation speed and the protein and oil concentration, respectively). The influence of the pH was also taken into account. Eventually, a relationship has been found that relates these properties to different composition (pH value, nature and concentration of proteins) or processing variables (agitation speed). (C) 2016 Elsevier Ltd. All rights reserved.

Surface tension properties of an enzymatically synthesized equimolar mixture of trehalose mono- and didecanoate in aqueous solutions have been determined. At 20 degrees C a critical micellar concentration (CMC) of 50 micromol/l and a minimal surface tension of 28 mN/m have been obtained. Above the CMC, it has been shown that up to a concentration of 42 wt%, and in a 20-60 degrees C temperature range the sugar ester aqueous solutions do not form any crystalline structure, nor present any phase transition, and the trehalose decanoate molecules form an isotropic worm-like micellar phase. The rheological properties indicate however a more complicated picture in the same concentration and temperature ranges. In steady shear, the viscosity of the trehalose decanoate solutions do not exhibit any shear rate dependence from 1 to 100 s(-1) for concentrations up to 42 wt%. Below 0.8 wt%, the viscosity remains constant and close to that of water; then, between 0.8 and 23 wt%, the viscosity shows a quadratic increase with surfactant concentration. For higher concentrations, up to 42 wt%, no further significant increase in viscosity is observed. In oscillatory shear experiments, the solutions exhibit viscoelastic properties. The observed rheological behavior as a function of concentration and temperature may be due to a progressive evolution of the trehalose decanoate molecular associations: as the concentration increases, the system evolves towards an entangled and/or partially branched or cross-linked micellar network, and eventually a multiconnected network of cross-linked micelles.

The rheo-reactor consists of a cylindrical vessel equipped with a double helical ribbon impeller installed in a RS150 controlled stress rheometer. It was used to investigate the rheological behaviour and the heat transfer in aqueous mineral residue suspensions during the phosphatation process. The absolute viscosity was determined using a Couette analogy allowing the quantitative analysis of the torque-rotational speed. The results show that the suspensions exhibit a viscoplastic or Binghamian behavior. The experimental operating conditions for the phosphatation process were then selected in order to ensure a good macro-mixing, even in laminar regime (Re < 30). Heat was generated as the combined result of the exothermic phosphatation process and the viscous dissipation inside the rheo-reactor. The heat produced needed to be efficiently removed to reduce its effect on the behaviour of the suspension. This was evaluated using the Nusselt number and the heat transfer coefficient h.

Hydrophobically associating alginate (AA) derivatives were prepared by covalent fixation of dodecyl or octadecyl chains onto the polysaccharide backbone (AA-C12/AA-C18). In semidilute solution, intermolecular hydrophobic interactions result in the formation of physical hydrogels, the physicochemical properties of which can be controlled through polymer concentration, hydrophobic chain content, and nonchaotropic salts such as sodium chloride. The mechanical properties of these hydrogels can then be reinforced by the addition of calcium chloride. The combination of both calcium bridges and intermolecular hydrophobic interactions leads to a decrease in the swelling ratio accompanied by an increase of elastic and viscous moduli. Beads made of hydrophobically modified alginate were obtained by dropping an aqueous solution of alginate derivative into a NaCl/CaCl2 solution. As compared to unmodified alginate beads, modified alginate particles proved to be stable in the presence of nongelling cations or calcium-sequestering agents. However, evidence is presented for a more heterogeneous structure than that of plain calcium alginate hydrogels with, in particular, an increase in the effective gel mesh size, as determined by partition and diffusion coefficient measurements.

Various amphiphilic derivatives of sodium alginate and hyaluronate were prepared by covalent fixation of long alkyl chains (dodecyl and octadecyl) with various ratios on the polysaccharide backbones via ester functions. In the semidilute regime, aqueous solutions of the resulting compounds exhibited the typical rheological properties of hydrophobically associating polymers: tremendous enhancement of zero shear rate Newtonian viscosity, steep shear-thinning behavior, and formation of physically cross-linked gel-like networks. The influence of the alkyl chain length, its content on the polysaccharide and of the polymer concentration in the solution was well identified. All obtained results are discussed with respect to the schedule of conditions related to materials, which could be used for cartilage repair, such as in synovial fluid viscosupplementation as well as in cartilage replacement. In particular, it is seen that HA-C(12)-5 (hyaluronate substituted with 5% of dodecyl chains) and HA-C(18)-1 (hyaluronate substituted with 1% of octadecyl chains) in a 0.15N NaCl solution at 8 g/L have rheological properties quite similar to those of healthy synovial fluid. On the other hand, the rheological parameters of solutions at 8 g/L in 0.15N NaCl of some of derivatives, such as, for example, AA-C(12)-8 (alginate substituted with 8% of dodecyl chains) or HA-C(18)-2, are well fitted for a use in cartilage repair.

We have developed a characterization method adapted to granular products based on conventional rheological techniques. We have used glass beads as model powders. By submitting a bed of glass beads to vertical vibrations, we have created conditions that can be seen as an equivalent Brownian motion at a macroscopic scale. We have obtained rheograms in both `steady-state' and `dynamic' regimes that can be interpreted in terms of equivalent viscosity and equivalent elastic and viscous moduli. In addition, we have shown that a solid–liquid transition can be observed depending on the vertical vibration frequency, in other term on the so-called granular temperature.

Rheological properties of granular materials are of paramount interest in many industrial operations involving mixing and handling. The determination of these properties implies suited characterisation methods elaboration. This paper aims at proposing such an experimental approach, based on statistical physic concepts and tested on model powders.

New hydrophobically associating water-soluble polymers have been prepared by covalent fixation of dodecyl and tetradecyl hydrocarbon side chains onto propylene glycol alginate (PGA). The viscosity of aqueous solutions of such deriatives is highly dependent not only on the shear rate but also on the shear time. The obtention of reliable data in this domain therefore requires that measurements are carefully carried out under steady state conditions. In the semi-dilute regime, intermolecular hydrophobic associations can be evidenced at low shear rates. These interactions result in considerably enhanced viscosities and the formation of physically cross-linked gel-like structures may ultimately be observed.