Continuing my recent theme of investigating the sometimes seemingly unusual ingredients that make up some of the most ordinary products. Last week focused on azodicarbonamide, a chemical used both in commercially baked breads as well as certain types of foamed plastics, such as yoga mats. Previously, we looked at how a typical plastic water bottle is manufactured, its journey from ink-black crude oil to a thin, clear plastic. This week we’ll investigate another product that is made from crude oil: laundry detergent. That’s right—the essential ingredient in many detergents that cleans your clothes is derived from an extremely dirty looking substance.
There are several main ingredients in detergents that help them get your clothes fresh and clean, and each serves a specific purpose. The main obstacle in cleaning your clothes is the type of dirt that needs to be removed. We’re humans, and our skin sweats. Sweat and other dirt and grease found on your clothing, however does not dissolve readily in water and therein lies the biggest problem of all. This means that we can’t just swish our clothes around in water and expect them to come out clean. That’s why we need a detergent with a chemical that will remove the dirt from fabrics.
We know that grease won’t dissolve in water—oil and water simply will not mix. We need something that will dissolve oils and dirt. Oils will mix with other oils, but we can’t wash our clothes in oil! We fill our washing machines with regular old water. So we need a chemical that can dissolve dirt and dissolve in water so it can carry all the dirt down the drain. Meet the main ingredient of laundry detergent: a surfactant. This dirt-removing chemical has some pretty neat properties that allow it to get dirt and grime out of our clothes.
There are many types of surfactants. The one pictured above is called a linear alkylbenzenesulfonate (I can’t pronounce it either…), a type of surfactant commonly used in laundry detergents. The special feature of a surfactant is that is has two distinct “ends”—a head and a tail. Its tail—the long zig-zag chain—is attracted to grease and oils. It’s hydrophobic (meaning that it repels water), but it will bind to the dirt in your clothes. The surfactant’s head, however, is attracted to water (hydrophilic). This is the part with the hexagonal shape in the picture. This is what allows the detergent to dissolve in wash water and carry the dirt away from the clothing (also known as lowering the surface tension of the water).
But where do linear alkylbenzenesulfonates come from? Crude oil, of course! Well, actually a chemical called benzene, which is a prominent component of crude oil. Another common place to find benzene: in gasoline (in small quantities). However, with a bit of chemistry, benzene can be transformed into a surfactant. And when combined with other ingredients that make up laundry detergent—such as enzymes that help break down dirt, bleaches that make clothes look brighter, and “antiredeposition agents” that prevent the dirt from going back onto the clothes—it makes for a very effective cleaning agent. Who would have thought?
Sources:
http://en.wikipedia.org/wiki/Laundry_detergent
http://en.wikipedia.org/wiki/Benzene
http://home.howstuffworks.com/laundry-detergent.htm
http://www.madehow.com/Volume-1/Laundry-Detergent.html#b
Thanks for the positive feedback!
@Kyle Thanks! I’m glad the posts are understandable; I think it’s about getting just the right amount of detail to explain the concept without overloading on information or technicalities.
@Sarah Shampoo was totally on my list to write about! Sometimes I get bored while I’m in the shower and try to pronounce the ingredients listed on my shampoo bottle. It’s quite a challenge… But I’ve always wanted to know more about what they are and what they do.
Ahh that kind of grosses me out a little. Great job! I would love if you wrote about shampoo and what is in it, because there’s a whole revolution of people who believe they shouldn’t use it.
Whoa! That’s super cool! I agree with what Kyle said above. I could definitely understand more of what you’re talking about because you explained the scientific concepts in a non-scientific way…or at least enough that anyone else was able to understand it upon first reading it. Keep up the good work!
Really cool post, Nick. You’re developing a knack, throughout this semester, of explaining difficult chemistry concepts in ways that non-chemists can understand or at least begin to wrap their heads around. Also: “surfactant” is totally the word of the day.