5 2. Polystyrene (PS) production and use Polystyrene (PS) is a widely used plastic with a range of applications. PS can be produced into several material types, although the majority of PS production is expanded polystyrene (EPS) and extruded polystyrene (XPS) foam. The global demand for PS reached 14.9 million tons in 2010, and the market for this material is expected to grow (EUMEPS, 2020). As a result of its high production and use, PS foam has become a major commodity, but also a major contaminant. PS foam is commonly reported as one of the top items reported in habitats and wildlife (Convey et al., 2002; Garrity and Levings, 1993; Hinojosa and Thiel, 2009; Morét-Ferguson et al., 2010). 2.1 PS production PS is as a simple compound manufactured from styrene monomer (C8 H8), which is formed when ethylene (C2 H4) and benzene (C6 H6) react in a polymerisation process (Gausepohl and Niesnser 2001). In its “raw” form, PS is a hard, transparent resin. From this basic form, PS can be transformed into different material types (i.e. foam, hard plastic, film) through processing, and can be made into a range of different materials from disposable goods to construction materials. For example, EPS and XPS are formed by different techniques that include “blowing agents,” causing PS to expand and making the material suitable for insulation and floats. PS materials can be comprised of different chemicals, some of which are used in processing or added as ingredients (Gortz 2001). The following section provides an overview of the different PS types, production, and use. 2.1.1 PS types The group of PS types comprises four main material types, including (1) expanded polystyrene (EPS) and extruded polystyrene (XPS), (2) clear, general purpose polystyrene (GPPS), (3) impact modified polystyrene (more commonly called high impact polystyrene (HIPS), and (4) syndiotactic polystyrene (sPS) (Gausepohl and Niesnser, 2001). The PS types and examples of use are summarized in Table 1. Expanded and extruded polystyrene (EPS, XPS) foam Expanded PS (EPS; also known as Styrofoam®) and extruded PS (XPS) are different types of foam produced from PS. EPS includes the most well-known and widely used products (i.e. packaging, single use food items), and XPS is a higher density, extruded material (Gausepohl and Niesnser, 2001). EPS and XPS are both common materials used for disposable goods, construction material, and dock floats. FOUR POLYSTYRENE TYPES Photos:Wikipedia Commons General purpose polystyrene (GPPS) General purpose PS (GPPS) is a hard-plastic copolymer, formed when PS is combined with other materials. Applications include toys, rigid packaging, CD cases, cosmetic packs, and laboratory materials (i.e. Petri dishes). Manufacturing GPPS is based on a bulk polymerization process (Gausepohl and Niesnser, 2001). Photos:Wikipedia Commons High impact polystyrene (HIPS) High impact PS (HIPS) is a hard-plastic copolymer, formed when PS is combined with other materials. Uses of HIPS include rigid and high- impact uses. Manufacturing HIPS is based on a bulk polymerization process similar to GPPS (Gausepohl and Niesnser, 2001). Photos:Wikipedia Commons Syndiotactic polystyrene (sPS) Syndiotactic PS (sPS) is a relatively newer type of PS and is a semi-crystalline polymer (Gortz 2001), and is used in electronics, including phones and electric vehicles. Photos:Wikipedia Commons Table 1: Four Polystyrene (PS) types.