Network flocculation and fractionation of latex particles by means of a polyethyleneoxide—phenolformaldehyde resin complex

Abstract

Flocculation of monodisperse latex particles by the sequential addition of a phenolformaldehyde resin and polyethyleneoxide has been investigated. It is suggested that flocculation takes place via a mechanical enmeshment mechanism in a transient hydrogen-bonded network formed by complexation of the two flocculating components. No flocculation takes place unless the latex dispersion is sensitized by the addition of cellulose fibers (collector). It is suggested that the role of the collector is to sweep the transient network and the therein entrapped particles before the network breaks apart (syneresis). Latex removal was found to be independent of latex concentration, but strongly dependent on latex particle size. Larger particles are more easily removed, thus establishing the network character of the complex formed. Experiments with latex particles of different sizes revealed the apparent mesh-size distribution of the transient network. It has also been demonstrated that the network can be used to fractionate mixtures of latex particles according to their size. A theoretical framework from which these network flocculation and fractionation phenomena may be understood is proposed.