Review on Identification, Recycling and Degradation of Polystyrene

Abstract

The main aim of this article is systematically to carry out comprehensive review on polystyrene, its identification, recycling and degradation. Polystyrene is a versatile plastic used to make wide variety of products. It is polymer of styrene and pentane which is blowing agent. Identification of polystyrene can be done through different methods like FTIR, GC-MS and DSC which gives satisfactory results. Various types of plastics have very slow degradation rate. It ranges from 10-1000 years depending on type of plastics. So there is need to recycle polystyrene. Commonly used recycling methods are chemical, mechanical and thermal recycling. These methods have their pros and cons. Recycled polystyrene has limited applications. So to control plastic pollution recycling and degradation of polystyrene both are important. Degradation of polystyrene with thermal, catalytic, supercritical solvent oxidation, photocatalytic and biodegradation are useful to convert it in less harmful component(s).

Introduction

Plastic Pollution and Polystyrene Overview

Plastic pollution is a significant global environmental problem, affecting ecosystems, climate resilience, and human livelihoods. Plastics, made of polymers, vary widely in type—common municipal plastics include polyethylene and polystyrene (PS), while others are industrial. Plastics degrade very slowly, sometimes taking decades to centuries, leading to massive accumulation in landfills and nature, with only a small fraction recycled.

Polystyrene (PS)

Polystyrene accounts for about 6% of global plastic production, with over 21 million tons produced in 2014. It exists in various forms such as general-purpose PS (GPPS), high-impact PS (HIPS), and expanded polystyrene foam (EPS or Styrofoam), widely used in packaging, insulation, electronics, construction, and medical fields. EPS is about 5% PS and 95% air, making it lightweight and insulating.

Chemical Properties

Polystyrene is a thermoplastic polymer with a backbone of hydrocarbons linked to phenyl groups, making it stable, chemically inert, and resistant to degradation. It has specific physical and thermal properties such as low moisture absorption, glass transition around 95ºC, and melting point around 240ºC.

Styrene Monomer

Styrene is the monomer used to make PS, produced mainly from petroleum derivatives. It’s a liquid with a sweet odor and polymerizes via several methods (radical, cationic, anionic, catalytic, and dispersion polymerization).

Identification Techniques

• FTIR Spectroscopy identifies chemical bonds in PS and tracks changes during degradation.

• GC-MS Analysis analyzes thermal degradation products, detecting styrene and related compounds.

• DSC measures thermal transitions like glass transition temperature, important for processing.

Recycling of Polystyrene

1. Thermal Recycling: PS can be broken down by pyrolysis at high temperatures, recovering valuable hydrocarbons and fuels. This method is energy-intensive and emits greenhouse gases.

2. Mechanical Recycling: Solid PS can be recycled without altering properties, but EPS requires volume reduction via solvents. Mechanical recycling often yields lower quality products and can be costly.

3. Chemical Recycling: PS foam can be chemically decomposed into styrene using catalysts like metal oxides. Chemical recycling is complex, expensive, and can involve toxic chemicals, limiting its widespread commercial use.

Conclusion

Due to increasing demand of polystyrene, there is increasing waste of polystyrene. In today’s world, the common polystyrene disposable place is in landfills. Due to its slow degradation rate, its impact causes severe danger to the environment. Recycling and degradation methods of polystyrene are not environment friendly and can harm the environment. Complete degradation of polystyrene may take five hundred years. So practically it is not possible to complete degrade polystyrene. The common degrading processes for polystyrene are thermal, catalytic, photocatalytic and super oxidative solvent oxidation but these are also not efficient processes to degrade complete polystyrene. To reduce the increasing pollution due to polystyrene, biodegradation is the only source. This review will help for further studies and encourage the scientist to research on biodegradation of polystyrene.

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Copyright © 2025 Vanshika Padiya, Bhushan R. Kavimandan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.