Polystyrene is produced by stringing together or polymerising the monomer styrene, which is derivative of petroleum. Styrene also occurs naturally in foods such as strawberries, cinnamon, coffee and beef.
A well-known property is that it is relatively chemically inert with high rigidity and high dimensional stability. It is also waterproof (with low moisture absorption) and soluble in solvents that contain acetone, such as most aerosol paint sprays, some glues and chlorinated solvents. It is highly flammable and has good electrical properties but has poor chemical and UV resistance. It is also a very good insulator, meaning that it quickly accrues electrical charge. This gives it a strong electrostatic attraction to other objects, causing it to readily stick to things.
It is used across industries in a variety of formats. It is a thermoplastic that is shapeless, transparent and colourless, making it incredibly versatile, as it can be combined with various colourants, additives or other plastics. It is used to make a wide variety of consumer products that require a hard, rigid material and it is also used in products that require clarity, such as food packaging, household appliances and laboratory ware.
One of its most popular Polystyrene formats is when it is made into a foam material, called expanded polystyrene (EPF). In this format it is especially valued for its insulating and cushioning properties. As a foam, polystyrene can be brittle and easy to break and crumble. Interestingly, it can even make a characteristic squeaky sound when rubbed. It is quite common to find polystyrene foam in the shape of small pellets or peanuts, as well as in sheet form. When manipulated by specialised machinery, its rigidity allows delicate but form-retaining structures to be created replicating the appearance of materials that are greater in weight and cost such as stones or marbles. Because of these qualities, polystyrene can be applied to a wide range of applications, including home furnishing and construction, prototypes and even props for advertising, window design and set design. Florists make use of EPF as the base to create their flower arrangements too.
An incredibly common use for Polystyrene is when shaped into a film. These films can be stretched into Oriented Polystyrene (OPS) which is cheaper to produce than alternatives like PP (Polypropylene), although it is more brittle. It is transparent and glossy which is why it is commonly used for food packaging as it enhances the contents within. With high hardness and great rigidity, OPS also provides better protection for the packaged products, and it can be produced in very thin sheets, which can greatly save in material costs.
When modified by the incorporation of elastomers, it becomes high impact Polystyrene or HIPS, which is often opaque. In it this form is tough, and rigid with high impact strength, as indicted by its name. It can be guillotined, punched, routered or sawn easily and is readily available in a wide variety of colours. Applications include the production of toys, packaging, and display signs.
The chemical structure of Polystyrene shows that it is composed of carbon and hydrogen atoms only. Therefore, it is classified as hydrocarbon.
It is extracted from oil. Thousands of small units of styrene, called monomers, link together to form large molecules of Polystyrene by a process called polymerisation. Expanded Polystyrene starts as small spherical beads with a typical diameter of 0.5-1.5mm.
EPF – Expanded Polystyrene Foam – can safely be incinerated and will release only carbon dioxide and water if the procedure is handled correctly. It can be recycled, although the material is usually refused by the curb side recycling programs because it contains more than 95% air, making it bulky to transport.
However, being a thermoplastic, it can actually be reused, remelted and remoulded into many different plastic items. The material, for example, can also be repurposed into concrete, egg cartons or new foam insulation.
Recycled Polystyrene is becoming a source of inspiration for artists and designers looking to reuse waste material, such as discarded polystyrene packaging, as a raw material for their artwork.
Polystyrene in art
Expanded polystyrene (EPF) is lightweight and versatile, making it the perfect material for sculpting. It is non-toxic and chemically inert, meaning it can be safely handled without specialised equipment. Often, EPS is covered in clay or other coatings, although it’s also possible to paint expanded polystyrene. With its consistent structure and sculpting ability, custom shapes and forms can be intricately created manually or with computer-controlled cutting machinery.