Polyurethane

Some plastics are very special.

They are made by mixing two things together. One part makes it strong. The other part can make it soft.

Scientists can add bubbles to the mix. This turns the plastic into a foam.

This foam is used for many things. It makes soft seats in cars. It also makes kitchen sponges.

It can even be used as hard insulation. This helps keep things warm or cold. It is a very useful material.

Polyurethane is a special group of plastics.

Most plastics are made of just one type of unit. But polyurethanes are made of two different parts joined together. These parts are called monomers.

Scientists make them by reacting two things: isocyanates and polyols.

By changing the mix, makers can make many things. They can make soft, stretchy fibers like spandex. They can also make hard, tough parts for cars. One of the most common uses is making foam.

To make foam, makers add a blowing agent. This is a substance that lets out gas. The gas creates tiny bubbles inside the plastic.

Some foams have open cells. These are tiny holes that let air flow through. This makes them soft for mattresses or cushions. Other foams have closed cells. These bubbles stay trapped inside. This makes the foam good for insulation to keep heat in. In 2016, foam made up 67% of all polyurethane made. This shows how useful these materials are in our world.

Polyurethane is a very useful group of plastics known as polymers.

Most common plastics like polyethylene are made of just one kind of unit. However, polyurethanes are different because they are made of two different parts. These parts are called monomers. These monomers join together in an alternating chain. This makes polyurethane a group of many different materials rather than just one thing. Because they can be made from many starting materials, they can have many different shapes and uses.

Making polyurethane is a specific way it works involving a chemical reaction. Scientists react a substance called an isocyanate with another called a polyol.

These two parts link together to form the polymer. To make foam, makers often add a blowing agent. This can be something like water. When water reacts with the isocyanates, it creates carbon dioxide gas. This gas forms tiny bubbles inside the plastic as it hardens. If the bubbles stay trapped, it is called a closed-cell foam. If the bubbles break but stay stiff, it is an open-cell foam.

People first discovered how to make these polymers a long time ago. Otto Bayer and his team at IG Farben worked in Leverkusen, Germany. They first made polyurethanes in 1937. This was a new way to make plastic that was different from older methods. Later, in 1952, isocyanates became available for more people to use. By 1954, companies began making flexible foam using toluene diisocyanate, or TDI.

There are many important numbers and facts about this material. In 2016, foams made up 67% of all polyurethane produced. By 2019, global production reached 25 million metric tonnes. This was about 6% of all polymers made that year. In 1960, more than 45,000 metric tons of flexible foam were made. In 1983, the Pontiac Fiero became the first car in the United States with a plastic body. This car used a process called reaction injection molding, or RIM.

You can find polyurethane in many things you use every day. It is used for soft seat cushions and mattresses. It is also used for tough shoe soles and car steering wheels. Some polyurethanes are even used as coatings to protect surfaces. You might see it in the stretchy spandex in your clothes. It even helps keep your home warm as insulation in walls.

Polyurethane, often abbreviated as PUR or PU, is a versatile class of polymers. Unlike common plastics like polyethylene or polystyrene, polyurethane refers to a whole group of materials. This is because they can be created from a wide variety of starting materials. These different materials result in many different chemical structures. Because of this variety, polyurethane can be used for many things. It can be a soft foam, a hard coating, or even a stretchy fiber like spandex.

The chemical process of making polyurethane involves a specific reaction. Scientists react a polymeric isocyanate with a polyol. An isocyanate is a molecule with two or more isocyanate groups. A polyol is a polymer that has two or more hydroxyl groups per molecule. During the reaction, these two types of monomers join together. They form an alternating chain of units linked by carbamate, also known as urethane, links. This makes polyurethanes alternating copolymers.

To create foam, makers use a process involving a blowing agent. This agent creates gas to expand the material while it hardens. One common method is adding small amounts of water. The water reacts with the isocyanates to create carbon dioxide gas. This gas forms bubbles within the polymerizing mixture. If the bubbles remain intact, the result is a closed-cell foam. These are often used for rigid thermal insulation. If the bubbles break but the edges stay stiff, it is an open-cell foam. These feel soft and allow air to flow through, making them great for mattresses.

The properties of the final product depend on the specific ingredients used. The type of isocyanate and polyol determines if the material is hard or soft. For example, long and flexible segments from a polyol create soft, elastic polymers. High amounts of crosslinking, which are chemical bonds between chains, create tough or rigid polymers. Short chains with many crosslinks produce hard materials. Long chains with intermediate crosslinking are useful for making foam.

The history of polyurethane began in Germany. Otto Bayer and his coworkers at IG Farben in Leverkusen first made these polymers in 1937. These new polymers had advantages over existing plastics. Early uses were limited, such as aircraft coatings during World War II. By 1952, polyisocyanates became commercially available. In 1954, flexible polyurethane foam production began using toluene diisocyanate (TDI) and polyester polyols.

As technology improved, polyurethane became part of many industries. In the 1960s, companies began using it for automotive interior safety parts. A new process called reaction injection molding, or RIM, was developed. In this process, reactants are mixed and then injected into a mold. This allowed for the creation of complex shapes like car body panels. In 1983, the Pontiac Fiero became the first plastic-body automobile in the United States. This was possible through reinforced RIM, which adds fillers like glass or mica to increase stiffness.

Polyurethane is a massive global industry with significant production numbers. In 2016, foams accounted for 67% of all polyurethane produced. By 2019, global production reached 25 million metric tonnes. This represented about 6% of all polymers produced that year. The industry also had to change due to environmental concerns. The Montreal Protocol restricted certain chlorine-containing blowing agents like CFC-11 because they harmed the ozone layer. In response, manufacturers moved to using blowing agents like carbon dioxide or pentane.