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

Bruna Torres Negreiros Cordeiro Andrade,Augusto Cesar Da Silva Bezerra,Claudinei Rezende Calado

doi:10.1590/s1517-707620190003.0732

Bruna Torres Negreiros Cordeiro Andrade, Augusto Cesar Da Silva Bezerra + Show 1 more

Open Access

https://doi.org/10.1590/s1517-707620190003.0732

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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.

Highlights

Polystyrene (PS) is a high molecular weight linear thermoplastic resin widely used in everyday life in a variety of applications ranging from packaging materials to electronic cabinets and household appliances, automotive and other industries
Sulfonated polymer solubility was used as a qualitative parameter for assessing whether the reaction products had different degrees of sulfonation
The results showed that polystyrene sulfonate (PSS)-expanded polystyrene (EPS)-02 was soluble in isopropylic alcohol and insoluble in water and dichloromethane

Summary

Introduction

Polystyrene (PS) is a high molecular weight linear thermoplastic resin widely used in everyday life in a variety of applications ranging from packaging materials to electronic cabinets and household appliances, automotive and other industries. PS is most often commercialized as a clear, odorless, hard, colorless, tasteless material that displays outstanding properties such as good mechanical strength, thermal stability, relatively low density besides its low production cost. Its structure of phenyl groups and single C-C bonds (Figure 1) makes polystyrene highly stable and resistant to decomposition. It presents good UV stability and resistance to gamma radiation which means PS is frequently used in products that require sterilization. The polymer is manufactured in three main commercial forms: general purpose polystyrene (GPPS) expanded polystyrene (EPS), high-impact polystyrene (HIPS) and a relatively minor grade syndiotatic polystyrene (SPS) [1,2]

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