Polystyrene critical flocculation temperature

Figure 8. Relationship between critical flocculation temperature(CFT) and concentration of HPC for polystyrene latex.

Experimental observation of selective flocculation. Croucher and Hair (1980a) have demonstrated the phenomenon of selective flocculation in mixtures of heterosterically stabilized dispersions. They prepared particles of poly(vinyl acetate) stabilized by polystyrene and polyacrylonitrile particles stabilized by polyisobutylene, both in cyclopentane. The value of X23 for polystyrene and polyisobutylene is known to be positive (Hyde and Tanner, 1968), corresponding to mutually incompatible polymers. The poly(vinyl acetate) particles stabilized by polystyrene exhibited both upper and lower critical flocculation temperatures whereas the polyisobutylene stabilized particles only flocculated on heating. 

When a mixture of the two different types of particles dispersed in cyclopentane was cooled to the lower critical flocculation temperature (280 K) of the poly(vinyl acetate) particles stabilized by polystyrene, those... 

Figure 9.15 Critical flocculation temperature values and 9 temj>eratures of polyethylene oxide (PEO) for polystyrene latex systems stabilized by adsorbed Pluronic in the presence of varying concentrations of KCl. Pluronic concentration, 200 ppm. From Tadros and Vincent [35]. 

Note that, as reported in Table 6.2, latices stabilized either by poly(a-methyl styrene) in -butyl chloride or by polystyrene in cyclopentane flocculated both on heating and on cooling. Moreover, the UCFT in nonaqueous systems tends to occur as the critical temperature of-the dispersion medium is approached. In aqueous systems, the UCFT can occur well below the critical temperature. 

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