Polystyrene (PS) is a cheap plastic used for moulded packaging and disposables, as well as a rigid foam, expanded PS (EPS). Both have their own unique set of qualities but may still be useful for the same applications, but for different reasons. For example, food containers – one thin and transparent, and the other an insulating and protective foam. While the monomer styrene is extremely hazardous and a known carcinogen, it is considered non-hazardous once polymerised. However, there may be instances where the monomer is not fully polymerised and can potentially leach out, such as into lipophilic food.

As a moulded plastic it has excellent transparency and resistance to water. It is predominately used in packaging and medical containers, as well as brightly coloured tableware and disposables. PS is brittle and will breakdown relatively quickly when exposed to sunlight, becoming yellow. Where transparency and durability are required, there are many alternative options available depending on the requirements, such as polycarbonate (PC), polymethyl methacrylate (PMMA), acrylic and polyethylene terephthalate (PET), polyester. Plastic free options include soda lime glass and borosilicate glass.

Expanded polystyrene (EPS) is a lightweight and rigid foam that provides excellent impact absorption and insulating properties. These qualities are utilised for packaging, safety and as a construction material. It provides an important role as insulation, saving energy throughout its life. However, it is quite voluminous and this presents some challenges with transportation and recycling. Only a very small percentage is PS (typically 2-5%), which means it may be considered too expensive or impractical to collect and recycle.