Caracterisation et modelisation de la dispersion de charges minerales dans une matrice polymere (French text)

In this work, dispersion mechanisms as breakup-agglomeration and erosion are seen as an infinite series of chemical reactions. A new model to represent these mechanisms is given. The proposed model uses agglomerate size population balance in its new mathematical formulation expressing agglomeration-breakup and erosion as an evolution of one particle subjected to mean-field type interactions with others. CaCO₃ agglomerates suspended in Polypropylene was used as a model compound to validate the proposed formulation.; The parameters of breakup or splitting and agglomeration processes were evaluated in well defined flow fields. For that, PP/CaCO₃ blends (fraction of CaCO₃ agglomerates suspended in PP) were extruded at high shear rates through different capillary dies. Shear rates ranging from 100 to 3180 s−1 were imposed to the blends. The agglomerate size distribution was analyzed before and after the capillary die. The changes in dispersion were only correlated to the generated deformation for the die alone. The breakup of CaCO₃ agglomerates was observed for shear rates higher than 160 s−1. k₁ , k₂, k₃, m, p and q are the breakup parameters. The coefficient of splitting frequency ( k₁) increased linearly with the shear rate.; The erosion parameters of CaCO₃ agglomerates were calculated from different size distributions obtained with a Haake internal mixer. Several mixing times and rotor speeds of the mixer were used to modify the size distributions. In this device the breakup of agglomerates was not observed due to the relatively low shear generated. The erosion parameter (k_e1) was also observed to increase linearly with the shear rate.; With breakup parameters evaluated through the capillary dies and the erosion parameters in the internal mixer, the model was applied to an industrial mixing device largely used “a Corotating Twin-Screw-Extduder”. In the latter, breakup and erosion of the agglomerates take place simultaneously. The model predictions and the experimental data were compared in several zones of the extruder. The results of the evolution of the dispersion along the TSE can be predicted with accuracy with the new formulation using the parameters evaluated in simple flows and in the internal mixer. The software LUDOVIC © was used to calculate flow parameters along the extruder.; Most of the experimental work consisted in the analysis of agglomerate size distribution. Many microscopic techniques have been used to characterize the dispersion. (Abstract shortened by UMI.)...