Adding value to polystyrene waste by chemically transforming it into sulfonated polystyrene

Abstract

Polystyrene (PS), one of the most used polymers in everyday life, has a low recycling rate due to its
inexpensive virgin resin. In order to make polystyrene waste (WPS) recycling advantageous, it is possible to
change it chemically, introducing heteroatoms in the polymer chain thus transforming the waste into a
material with more added value. In this work, sulfonation reactions of polystyrene waste (disposable cups
and expanded polystyrene - EPS) with different degrees of sulfonation were carried out by homogeneous
sulfonation using acetylsulfate as a sulfonating agent, originating polystyrene sulfonate (PSS). The
characterization of the products was done using Fourier Transformed Infrared Spectroscopy (FTIR),
solubility tests and inductively coupled plasma optical emission spectroscopy (ICP-OES). Infrared
spectroscopy revealed that the reaction was efficient and all the starting materials tested were successfully
sulfonated and transformed into PSS. There was no distinction between the residues tested, revealing that it's
possible to carry the reaction without sorting the waste. EPS was chosen as the substrate for further reactions
varying the degree of sulfonation. Solubility and ICP-OES tests have shown that, by changing the synthesis
conditions, it is possible to achieve different degrees of products sulfonation. As a result of the studied
reactions it was found that varying the degree of sufonation it is possible to use polystyrene residues to
produce PSS for different applications.
Keywords: Polystyrene, Waste, Sulfonated polystyrene, Sulfonation, Recycling, Expanded polystyrene.