Polystyrene facts for kids

Quick facts for kids Polystyrene
IUPAC name	Poly(1-phenylethene)
Other names	Thermocol
Identifiers
Abbreviations	PS
CAS number	9003-53-6
Properties
Molecular formula	(C8H8)n
Density	0.96–1.04 g/cm3
Melting point	240 °C, 513 K, 464 °F
Solubility in water	insoluble
Solubility	Soluble in acetone
Thermal conductivity	0.033 W/(m·K) (foam, ρ 0.05 g/cm3)
Refractive index (nD)	1.6; dielectric constant 2.6 (1 kHz – 1 GHz)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Polystyrene a type of plastic. More specifically, it's a polymer used for a wide variety of packaging. It is made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry. Polystyrene is one of the most widely used plastics, the scale being several billion kilograms per year.

Discarded polystyrene does not biodegrade for hundreds of years and is resistant to photo-oxidation.

Restricting the use of foamed polystyrene takeout food packaging is a priority of many solid waste environmental organisations. Efforts have been made to find alternatives to polystyrene, especially foam in restaurant settings.

History

Polystyrene was discovered in 1839 by Eduard Simon, an apothecary from Berlin, but it wasn't until the 1930s that scientists figured out how to make it on a large scale.

How is polystyrene made?

Making polystyrene involves a process called polymerization. This is where those tiny styrene monomers are linked together to form the long chains. The process usually involves heating the styrene monomers under specific conditions with a special "helper" molecule called an initiator. This initiator helps the monomers connect to each other, forming the long chains of polystyrene.

The type of polystyrene produced depends on how the polymerization process is controlled. This leads to different types of polystyrene with different properties.

Types

• General Purpose Polystyrene (GPPS): This is the type of polystyrene you often see in disposable cups, plates, and food containers. It's clear, brittle, and relatively inexpensive to produce. It's lightweight and easy to mold into different shapes, which is why it's so popular for packaging. GPPS was first commercially produced in the 1930s, and its use quickly expanded due to its affordability and versatility. By the 1950s, it was a common sight in homes and businesses across the world.

• Expanded Polystyrene (EPS): This is the type of polystyrene you see in those familiar white packing peanuts. It's also used in insulation for buildings and coolers. EPS is made by adding a blowing agent to the polystyrene during the polymerization process. This blowing agent creates tiny bubbles of air inside the polystyrene, making it much lighter and less dense than GPPS. The first commercial production of EPS was in the 1950s, and its use quickly grew due to its excellent insulation properties and lightweight nature. Think about how much lighter a package is with EPS peanuts compared to using something like cotton!

• High Impact Polystyrene (HIPS): This type of polystyrene is tougher and more resistant to breaking than GPPS. It's often used in things like appliance casings and toys. The addition of a rubbery material during the manufacturing process gives HIPS its increased strength and flexibility. HIPS was developed later than GPPS and EPS, and its use has steadily increased due to its improved durability.

Forms produced

Polystyrene is commonly injection molded, vacuum formed, or extruded, while expanded polystyrene is either extruded or molded in a special process. Polystyrene copolymers are also produced; these contain one or more other monomers in addition to styrene. In recent years the expanded polystyrene composites with cellulose and starch have also been produced. Polystyrene is used in some polymer-bonded explosives (PBX).

Properties

Polystyrene has several properties that make it so useful:

• Lightweight: It's much lighter than many other materials, making it ideal for packaging and transportation. This saves on fuel costs and reduces the environmental impact of shipping goods.

• Inexpensive: It's relatively cheap to produce, making it accessible for a wide range of applications.

• Easy to mold: It can be easily molded into various shapes and sizes, making it versatile for different products.

• Good insulator: Expanded polystyrene (EPS) is an excellent insulator, making it perfect for keeping things cold or warm. This is why it's used in coolers, building insulation, and even in some types of coffee cups.

• Water resistant: Polystyrene doesn't absorb water, making it suitable for use in wet environments. This is why it's often used in disposable food containers.

Environmental impact

Because polystyrene is a plastic, it doesn't break down easily in the environment. This means that polystyrene waste can persist for many years, even centuries. This is a significant concern, as it contributes to pollution in landfills and oceans.

Animals do not recognize polystyrene foam as an artificial material and may even mistake it for food. Polystyrene foam blows in the wind and floats on water, due to its low specific gravity. It can have serious effects on the health of birds or marine animals that swallow significant quantities.

Interesting facts about polystyrene

• Discarded polystyrene does not biodegrade for hundreds of years and is resistant to photo-oxidation.
• Whether polystyrene can be microwaved with food is controversial. Some containers may be safely used in a microwave, but only if labeled as such.
• Like other organic compounds, polystyrene is flammable. Foamed polystyrene plastic materials have been accidentally ignited and caused huge fires and losses of life.
• In 1988, Suffolk County, New York, became the first U.S. jurisdiction to ban polystyrene in general.
• In 2015, researchers discovered that mealworms, the larvae form of the darkling beetle Tenebrio molitor, could digest and subsist healthily on a diet of EPS. About 100 mealworms could consume between 34 and 39 milligrams of this white foam in a day. The droppings of mealworm were found to be safe for use as soil for crops.
• A March 2022 joint study by scientists Sewon Oh and Erin Stache at Cornell University in Ithaca, New York found a new processing method of upcycling polystyrene to benzoic acid. The process involved irradiation of polystyrene with iron chloride and acetone under white light and oxygen for 20 hours.

Images for kids

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  A polystyrene yogurt container

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  Bottom of a vacuum-formed cup; fine details such as the glass and fork food contact materials symbol and the resin identification code symbol are easily molded

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  Polystyrene is flammable, and releases large amounts of black smoke upon burning.

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  Extruded polystyrene has a smooth texture, and can be cut into sharp-edged shapes without crumbling

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  Polystyrene waste

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  Coastal debris including polystyrene

See also

In Spanish: Poliestireno para niños