Flocculation of cellulose fibres: new comparison of crowding factor with percolation and effective-medium theories

New comparisons of percolation and effective-medium theories on one hand, and predictions from the crowding factor on the other hand, are described for calculating critical concentrations in suspensions of cellulose fibres. The connectivity threshold from percolation theory appears to correspond to the gel crowding factor, which occurs at crowding factor (N) of N = 16 rather the criterion for fibre collisions, N = 1, postulated in earlier work. The rigidity threshold from percolation theory corresponds to the onset of coherent fibre flocs having mechanical network strength, which occurs at about N = 60. The latter value exceeds the gel crowding factor value by a factor of 3.75. In comparison, percolation theory predicts that flocculation occurs at a rigidity concentration four times higher than the connectivity threshold. These ratios are in good agreement.