Contribution of static light scattering to the textural characterization of large aggregates.

The industrial processes of water clarification often imply flocs of millimeter length. The principal motivation of this work relates to the characterization of these large flocs with laser diffractometry, for which the authors propose particular experimental approaches. In addition, a reformulation of the various properties of the flocs accessible by laser diffractometry is presented, in particular for the determination of the size, density, porosity, volume fraction, and fractal dimension. By way of illustration, these experimental and theoretical developments are applied to the characterization of flocs obtained by flocculation of a commercial kaolin. The size, fractal dimension, and density of kaolin floc were examined under various flocculant concentrations. Measurements reveal important variations of the granulometric and textural properties of large flocs in response to flocculation, opening ways of optimization for the associated industrial processes.

Influence of the morphogranulometry and hydrophobicity of talc on its antisticking power in the production of tablets.

Antisticking power varies according to the talc considered. It is difficult to define the physical properties of talc implicated in its antisticking power. In this work, different talcs were characterized and an evaluation made of their performance in reducing sticking in tablet manufacturing. Determination of the specific surface area was made by permeametry, morphogranulometric analysis by laser diffractometry using a method, which made it possible to assess the mean thickness of talc particles, and measurement of water absorption kinetics was taken to assess hydrophobicity. The relationship between the characteristics of talcs and their antisticking power was then considered. There is a correlation between the particle size of talc and surface hydrophobicity. The detaching force of tablets appears to be dependent on the basal dimension of talc.

Relation between structural characteristics of talc and its properties as an antisticking agent in the production of tablets.

Antisticking power varies according to the talc considered. Besides its chemical properties, it is necessary to assess its physical properties related to functionality. It is difficult to define the physical properties of talc implicated in its antisticking power. In this work, different talcs were characterised and their performance in reducing sticking in tablet manufacturing was evaluated. The following parameters were studied: apparent density, morphogranulometry, roughness, and the specific surface through the adsorption-desorption of argon. Next, the relationship between the characteristics of talcs and their antisticking power was considered. Talc before and after delamination-which is a way to obtain talcs with different physical characteristics-was compared. Antisticking power appeared to be dependent on the basal dimensions of talc, and on the ratio value of the external specific surface measured by diffractometry to the total specific surface by the BET method. Models to express the effect of textural factors of talc particles on antisticking power were defined.