Observation and analysis of the infiltration of liquid polymers into calcium carbonate agglomerates

The dispersion of fine particle agglomerates in liquid polymer melts is inf luenced by the penetration of liquid into the agglomerates. It is therefore of great importance to determine the extent of polymer impregnation that c an be achieved during a typical processing operation. This paper studies th e infiltration of calcium carbonate agglomerates by various polymeric liqui ds. The kinetics of infiltration was gauged using sedimentation experiments performed in the impregnating Liquids. Experimental infiltration curves pr oved to be well-described by a theoretical relationship based on Darcy's la w. This model was first applied assuming full saturation of the infiltrated outer layer of the agglomerate and it was considered that there was no air pressure build-up inside the dry core of the agglomerate. These assumption s had to be relaxed to account for the differences in infiltration rate obs erved for polymers of different chemical nature. For some of the fluids [et hylene-propylene random copolymer (EP) and styrene-butadiene random copolym er (SBR)], a partially saturated infiltrated region was envisioned. Assumin g that poly(dimethylsiloxane) (PDMS) was able to fully saturate the agglome rate infiltrated layer, lower degrees of saturation (about 0.9) were found in the case of EP and SBR. These estimations were obtained considering that residual air reduced the effective permeability of the agglomerate to the polymer. A classical power law relationship was used to link this effective permeability to the degree of saturation of the infiltrated region. (C) 19 99 Elsevier Science S.A. All rights reserved.