Polyethylene and polyurethane are two types of plastic materials used to manufacture a wide range of items, including common consumer goods. There are, however, some distinct differences between these materials in both chemical composition and how they are used.
Polyethylene is among the most widely used plastic polymers. In fact, when most people describe something as being made of the generic term "plastic," chances are they're describing polyethylene. Polyethylene is used to manufacture items such as shopping bags, toys, shampoo bottles and even bulletproof vests. Chemically, the structure of polyethylene is the simplest of all commercial polymers. It consists of a long chain of carbon atoms with two hydrogen atoms attached to each carbon atom.
Polyurethane typically is used to manufacture foam, such as the kind found in padded furniture. However, polyurethane also is a highly versatile polymer. In addition to foam, polyurethane can be a fiber and an elastomer because of its elastic properties. Polyurethane is used to manufacture paints and adhesives. It also is a key component in spandex and lycra, stretchy man-made materials typically used in clothing.
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Polyethylene was discovered in 1933 by Reginald Gibson and Eric Fawcett, two researchers at Imperial Chemical Industries, a British industrial firm. In addition to the low cost of producing polyethylene, the material also was found to be flexible, durable and resistant to chemicals. Polyurethane was invented a few years later by Dr. Otto Bayer in Germany. After the end of World War II, polyurethane became widely used in blown form for mattresses, furniture padding and insulation.
Polyethylene is a thermoplastic resin, which means an item made with the material can be recycled, melted down and reformed into another shape. Polyurethane, on the other hand, is a thermoset resin, meaning that it has two parts mixed together to form a chemical chain. Once polyurethane is cured, the process can’t be undone. This means that something made of polyurethane can’t be melted down and reformed into a different item.