Different components of granulated plastic mixtures can be separated by froth flotation. This technique involves selective adherence of gas bubbles onto the particles to be separated. This requires a sufficient difference in the wettability of the particles. Since the overwhelming majority of plastics are hydrophobic by nature, separation by flotation necessitates selective wetting of the components. However, a comprehensive understanding of wetting phenomena involved has not been established thus far, so that the wetting action of surfactants during flotation cannot be predicted. As a consequence, selection of suitable wetting agents is essentially based on trial-error test work. However, the test work needed can largely be reduced by more insight into the wetting mechanisms involved which is the subject of the present work.