Flocculation studies

Flocculation studies, considering the small-strain mechanical response of the uncross-hnked composites during heat treatment (annealing), demonstrate that a relative movement of the particles takes place that depends on particle size, molar mass of the polymer, as well as polymer-filler and filler-filler interactions (Figure 22.2). This provides strong experimental evidence for a kinetic cluster-cluster aggregation (CCA) mechanism of filler particles in the mbber matrix to form a filler network [24]. 

Flocculation studies (6) indicated that the mechanism of steric stabilization operates for the PMMA dispersions. The stability of PMMA dispersions was examined further by redispersion of the particles in cyclohexane at 333 K. Above 307 K, cyclohexane is a good solvent for PS and PDMS, and if the PS-PDMS block copolymer was not firmly anchored, desorption of stabilizer by dissolution should occur at 333 K followed by flocculation of the PMMA dispersion. However, little change in dispersion stability was observed over a period of 60 h. Consequently, we may conclude that the PS blocks are firmly anchored within the hard PMMA matrix. However, the indication from neutron scattering of aggregates of PS(D) blocks in PMMA particles may be explained by the observation that two different polymers are often not very compatible on mixing (10) so that the PS(D) blocks are tending to... 

VI Flocculation Studies, Critical flocculation temperatures were measured using suspensions of 0.6% v/v latex containing the appropriate amount of sodium chloride. Differing degrees of neutralisation were produced by the addition of NaOH to stock solutions and checked by conductometric titration with base in the absence and presence of added HC1. Flocculation temperatures (CFT) were determined by visual observation at a cooling/heating rate of M).5 C s. The flocculation was generally reversible provided that the latices had not been left in the flocculated state for more than a few minutes or so. 

Flocculation studies were performed by lowering the temperature of PMMA dispersions in a binary mixture of n-heptane and... 

In the last three chapters we dealt with the theoretical predictions of the magnitudes of steric interactions and their dependence upon distance. The incipient flocculation behaviour that was discussed in Chapters 5-9 is determined primarily by the magnitude and the sign of these steric interactions. Incipient flocculation studies, however, do not provide direct information about the distance dependence of the interaction. An additional drawback is that it is inevitable in incipient flocculation experiments that the dispersions be studied under conditions of pathological instability. This may change the very properties that we wish to study in order to determine how stability is imparted. It is therefore necessary to complement the incipient flocculation experiments with studies on dispersions that exhibit robust stability. 

FREE POLYMER AND COLLOID STABILITY EXPERIMENTAL 361 16.2.4.2. Flocculation studies... 

Krogerus B (1993) Dynamic flocculation studies on fibre fines and filler clay. Nordic Pulp Paper Res J 8 135... 

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