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Polystyrene balls are tiny polymer molecules that have been infused with air to increase their size. The polymers used to form these molecules are derived from petroleum by-products through a distillation and refining process. Once they have been infused with air, the balls can be joined together to form larger beads, or molded into products ranging from foam building insulation to food packaging.
The polymers used to form polystyrene balls start off as molecules measuring just 0.02 inches (0.5 mm) in diameter. They are subject to a steam process that infuses air into the molecule to create a much larger polystyrene bead. These are the same foam beads found in the average bean bag chair. If the beads are placed into a mold or extruded through a die, they can be joined together to form much larger products. In the average polystyrene product, the polymer molecules have been infused with so much air that the air makes up a much greater percentage of the material's makeup than the polymer itself.
One of the primary advantages to polystyrene balls is that they are incredibly lightweight. Despite their air-infused nature, they are also very strong and durable. While polystyrene is widely used because of these benefits and its low cost, many critics voice concerns about the long life of this product. Polystyrene is tough to recycle, and can last for centuries in a landfill.
Loose polystyrene balls are used to fill bean bag chairs or toys. When molded or extruded, they are also used to make product packaging, including packing peanuts and the hard foam casing used to protect electronics. This material is used to make hot food containers found in carryout restaurants, as well as disposable cups and plates. Polystyrene can even be formed into dense sheets of foam that are used to insulate buildings.
The polystyrene balls used in arts and crafts materials are made using a slightly different technique than those used in food packaging and insulation. These beads are pre-expanded and treated with solvents before they are steamed, resulting in a dense material that creates a crunching sound when it is cut or damaged. They are used to make many products used in art projects, including balls as small as a marble or as large as a basketball. Manufacturers also form polystyrene balls into various shapes, such as Easter eggs or animals, which can be painted or decorated. This type of polystyrene also serves as a stable base material for artificial flowers, such as the bouquets used as grave markers.