The influence of solutions of NaOH and plasticizers on the wettability of PVC and PET plastics

Abstract

Flotation of plastics becomes a very prospective method of their separation as a reflection of the industrial quality of purity requirements. The problem is however that most of the plastics have relatively similar hydrophobic surfaces preventing them to be selectively sorted by the flotation method. That is why various ways have been proposed in order to stimulate the wetting of the plastics´ surfaces selectively (gamma flotation, selective adsorption of wettting substances or depressants, physical treatment, and chemical treatment). Unfortunately, the application of traditional use of depressants is questionable since there are different or even contrast theoretical explanations of their adsorption mechanism on the plastics´ surfaces. In this article, a brief theoretical overview is presented summarizing the possible mechanisms of the selective adsorption of organic depressants from the standpoint of modern surface thermodynamics approaches. On the other hand, the method of chemical treatment of the plastics´ surfaces known as the selective hydrophobic modification is better studied and so understood. Therefore, the influence of NaOH solutions as well as of two plasticizers (diisodecyl phtalate and diethylen glycol dibenzoate) on the surface wettability of PVC and PET plastics has been studied experimentally.

Keywords

• flotation
• plastics
• adsorption