Croatica Chemica Acta, Vol. 52 No. 1, 1979.
Original scientific paper
Studies on Polytetrafluoroethylene Latices. Part 2. Coagulation by Hydrolysable Electrolytes
R. H. Ottewill
; School of Chemistry, University of Bristol, Bristol BSB 1TS, England
D. G. Rance
; School of Chemistry, University of Bristol, Bristol BSB 1TS, England
Abstract
The colloidal stability of polytetrafluoroethylene (PTFE) latices
has been examined as a function of pH at different concentrations
of aluminium nitrate. The basic behaviour observed can be subdivided
into three pH domains, lower than· pH 3.3, pH 3.3 to 5.2 and
pH 5.2 to 7.5. In the lowest pH region, coagulation of the latex
appeared to occur as a consequence of compression of the electrical
double layer by a 3 : 1 electrolyte. In the pH region 3.3 to 5.2 cationic
polynuclear aluminium ions were formed which adsorbed on the
particles and neutralised the charge on the negative latex particles.
Charge reversal and restabilization of the latices as cationic particles,
however, was not observed. The appeared to be a consequence
of the relatively high charge reversal concentration and the possible
weak adsorption of polynuclear species on the PTFE surface. Coagulation
in the pH region 5.2 to 7.5 appeared to be the consequence of
several mechanisms operating together.
Keywords
Hrčak ID:
195906
URI
Publication date:
19.4.1979.
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