SYMMETRICAL AND ASYMMETRICAL FLOW FIELD-FLOW FRACTIONATION FOR PARTICLE-SIZE DETERMINATION

Measurements on paint components have been conducted with symmetrical flow field-flow fractionation (sym flow FFF) and asymmetrical flow FFF (asym flow FFF). Both methods are based on the same principle of sepa ration, but they differ in the construction of the fractionation chann el and the configuration of the channel flow and crossflow. On the bas is of the good selectivity and resolution of these techniques, it was possible to determine the particle size of each individual constituent of a three-component mixture of a paint binder, pigment and filler, c haracterized by relatively broad and overlapping distributions, and to follow the changes on mixing them. In the case of sym flow FFF, it wa s possible to use thinner fractionation channels, with no system peaks and good selectivity in both the normal and steric-hyperlayer mode. T he main features of asym flow FFF are the simpler construction of the fractionation channel and the possibility of focusing the sample in th e channel better and of following visually the separation. This varian t should be preferably used in the normal mode of operation.