EVALUATING THE WETTING (SURFACE POLARITY) AND ROUGHNESS OF PET FOILS SURFACE DEGRADED BY INCIPIENT ALKALINE HYDROLYSIS

One of the ways to weaken the inherently hydrophobic surface of plastics from the view of flotation separation is the application of alkaline hydrolysis. A pretreatment in NaOH solutions at low temperatures and/or concentrations of up to 60 °C and 8 %, respectively, for 20 minutes has been found to be efficient to decrease the surface hydrophobicity of PET foils to such an extent that their flotation ability is entirely depressed. Such a hydrophilization pretreatment also stimulates the PET's surface roughness, wetting of the surface and the thermodynamic equilibrium conditions at the surface and ultimately changes surface charge (polarity). [PUBLICATION ABSTRACT]