It is an indisputable fact that various synthetic polymer materials such as plastics and rubber are ubiquitous in our lives. However, among the many polymer materials, perhaps none can penetrate into every corner of our lives like polyurethane. Maybe you’re curious, where is this unfamiliar-sounding material? Then please follow me to find its footprints in every day life.
After breakfast, you walk to the kitchen after washing up. When you are about to take out today’s breakfast from the refrigerator, you might as well think about what is inside the thick box and door of the refrigerator. The answer is polyurethane foam. The cold air inside can’t come out, and the hot air outside can’t get in? The answer is polyurethane foam sealed in the refrigerator box and door. They try their best to prevent the exchange of heat inside and outside the refrigerator. Without polyurethane, the compressor of the refrigerator would roar endlessly, and you would have to worry about the huge power consumption of the refrigerator.
Next, please turn your attention to the plywood cabinet next to the refrigerator. Plywood is made of many layers of thin wooden boards bonded with glue. Phenolic resin and urea-formaldehyde resin were once the main methods for bonding wooden boards. However, these two types of materials release formaldehyde, which has strong carcinogenic effects, so they have been used in recent years. Replaced by polyurethane. Finally, please move your eyes to the corner of the wall. The polyurethane sealant is faithfully performing its duty and firmly sealing the gap in the corner.
After breakfast, you leave home and come to your work. The company has just moved into a new office building. When walking into the lobby, the solid wood floor is as bright as a mirror. This is thanks to a layer of polyurethane paint covering the floor. Otherwise, the wooden floor would have been worn out by the flow of people. .
You notice eye-catching posters posted in the company’s corridors, proudly announcing to everyone that the company’s new office building is a model in terms of energy conservation despite its large area and luxurious interior decoration. Reducing the energy consumption of buildings requires many efforts, but one big contributor is the polyurethane foam sandwiched inside walls and ceilings. They are very similar to the polyurethane foam used in your refrigerator, except here they are used for larger “Fridge” provides services.
After hard work, you come to the sports field to prepare for some exercise. Is there any trace of polyurethane in this? Of course there is. Let’s talk about the sportswear you wear first. Why does it fit snugly around your body without losing comfort? If you pay attention to its label, you may notice the words “10% spandex”, and the answer is here. Spandex is a polyurethane fiber with extremely excellent elasticity. Although the content of spandex in clothing fabrics is generally not high, without it, clothes such as swimsuits, sportswear and leggings will feel very bad when worn on the body. Let’s talk about these sneakers on your feet.
The comfortable and wear-resistant soles of many shoes are made of polyurethane, and polyurethane soles often rely on polyurethane adhesives to firmly adhere to the uppers. Next, let’s talk about the plastic track under your feet. The basic raw material of the plastic track is of course waste rubber crushed into small particles, but without the polyurethane adhesive to tightly connect them together, these small rubber particles will just fly everywhere like sand.
Night falls and you return home. A tiring day has finally ended. At this moment, you may be lazily leaning on the sofa and watching TV programs, or lying on your own big bed and getting ready to fall asleep. If you peel back the fabric on a mattress or sofa cushion, you may see a white or creamy yellow soft and light material, which is still polyurethane. Polyurethane plays an important role in making mattresses and sofa cushions so comfortable.
Finally, when you and your lover enjoy the intimate world of two people, don’t forget another important contribution of polyurethane, that is, condoms. Although polyurethane is not the mainstay of condom production – most condoms are made from natural rubber, polyurethane provides a very good alternative for those who are allergic to natural rubber.
Figure 1 Several important applications of polyurethane: Upper left: mattress; Upper right: shoe sole; Lower left: coating; Lower right: elastic fiber
Through the above introduction, have you realized that almost every aspect of our daily work and life is inseparable from polyurethane? So what kind of magical material is this, and how do we get it?
As we all know, various synthetic polymer materials are produced by the reaction of countless small molecules. For example, polyethylene is the product of the reaction of ethylene molecules. Polyurethane is naturally no exception. To obtain it, two important types of small molecules are indispensable.
This molecule is called an alcohol, which is a compound with a hydroxyl group [1]. This is a type of substance that everyone is very familiar with. Every time we drink happily, we are drinking ethanol, a kind of alcohol. HoweverIt recovers its own shape and therefore brings great comfort to the user. Many of the mattresses and sofa cushions mentioned earlier use this type of polyurethane foam. In addition, car seat cushions are also indispensable.
Another kind of polyurethane foam is harder, and the tiny holes inside are no longer connected, but isolated from each other. What is the use of such a foam? We know that if we want to insulate the spread of heat, no material can be as effective as air, and the heat-insulating ability of carbon dioxide in the air is much better than other components such as oxygen and nitrogen. If we use polyurethane to isolate carbon dioxide in tiny spaces to prevent them from flowing through each other or escaping to the outside world, such polyurethane foam has good thermal insulation capabilities that are almost as good as air, which is difficult to match with other materials.
If bricks are used instead, the insulation effect of bricks more than 30 centimeters thick can be equal to that of polyurethane foam 1 centimeter thick! And because polyurethane foam has good mechanical strength, using it for thermal insulation is often much better than simply using air for thermal insulation, so it is widely favored by people. Polyurethane foam has not only become a necessity for the production of refrigerators, but is also widely used in building energy conservation. These polyurethane foams effectively help us improve energy utilization, thereby saving valuable resources.
Figure 4 Operators are using polyurethane foam to improve the insulation capacity of the building
From its birth to the present, polyurethane has gone through a process of nearly 80 years and has greatly changed our lives. Looking to the future, the continuous innovation and progress of polyurethane materials will make our lives better.
Note:
[1] To be precise, alcohols are compounds in which an aliphatic carbon chain is linked to a hydroxyl group. Compounds in which the hydroxyl group is directly attached to the benzene ring are called phenols.
[2] Diphenylmethane diisocyanate has three different structures: 2,2′, 2,4′ and 4,4′. Among them, 4,4′-diphenylmethane diisocyanate is commonly used in the polyurethane industry. Figure 1 also shows this structure.
[3] Many polyurethane foams also have other gases introduced during the production process to help foaming
