TABLE OF CONTENTS In this method a solution or dispersion of a plastic is stirred into at least 10 times its volume of a solvent, which acts as a precipitant for the dissolved plastic but which dissolves completely in the first solvent. The precipitated plastic is pulverised and repeatedly extracted with the precipitant/solvent or re-dissolved and precipitated.
Or a non-solvent is added to a solution of the plastic until the first faint turbidities appear due to the high polymer plastic components. The solvent is then reduced on a water bath or by vacuum distillation. The solvent and the non-solvent must be completely miscible and the solvent must have a lower boiling point than the non-solvent.
Or the plastic is dissolved in a solvent, which dissolves the plastic at higher temperatures - the plastic separates out on cooling while the additives remain in solution.
Or plastic dispersions can often be separated by stopping the action of the emulsifier and/or dispersing agent, i.e., breaking the emulsion. The following methods can be used according to the type of emulsifier:
Alteration of the solvent phase.
Precipitation of the emulsifier by the addition of acids or a interfacially active counterion.
Freezing the dispersion out with solid carbon dioxide.
Subjection of the dispersion to dialysis, whereby the water-soluble inorganic salts and relatively low molecular emulsifiers are diffused through cellophane membranes so that the protective colloid and the polymer can now be easily separated quantitatively by...
