The stuff in the dryer sheet happens to be good at both jobs. You can obtain the static-elimination function all by itself as a liquid in a spray can, so you can de-static your clothing even while you’re wearing it without your having to, DO NOT TRY THIS AT HOME!, climb into the dryer.
The main ingredient in both types of products is a surfactant, a chemical that is made of what might be called bisexual molecules; they are attracted to both oil and water. Most other chemicals show a strong preference for one or the other.
For example, common salt (sodium chloride) is made of electrically charged atoms (Techspeak: ions), and charged atoms like to mix into, dissolve in, water because water molecules have electric charges that attract them. But salt won’t have anything to do with fats and oils because their molecules don’t have any attractive charged parts. Just try to dissolve some salt in olive oil and see how far you get.
Surfactants, however, are peculiar in that one end of each molecule is a fatty material that is attracted by oils, while the other end is charged and is attracted by water. Soap and detergent molecules are surfactants; their oil-loving ends latch on to oily dirt and drag it into the water by means of their water-loving ends. Or looking at it the other way, their water-loving ends drag water into oily places that it wouldn’t ordinarily invade, thereby making the water wetter.
Now let’s impregnate a paper sheet with a soapy-feeling surfactant chemical and throw it into the dryer along with our wet clothes. As they tumble, the clothes rub against the sheet and become coated with surfactant. The rather hefty fatty ends of the surfactant molecules impart a slippery, waxy feel to the clothes, “softening” them.
Then when the clothes begin to dry, their friction against one another rubs off some electrons and static electricity begins to build up. The charges can’t build up as long as the clothes are wet because water conducts electricity well enough to conduct the rubbed-off electrons back to where they came from. When the water is gone, the charged ends of the surfactant molecules take over, conducting the charges away and killing any “static cling” that might result.
Deprived of their static cling, socks find themselves unable to bond with their partners and may suffer a severe separation-anxiety syndrome. In fact, a sock may become so depressed and emotionally unraveled that it will slink away through the vent tube in search of psychiatric help. That’s why you will sometimes find a sock missing when you put away your laundry. I know you have wondered about that.
There are three kinds of surfactants whose names you will see as ingredients on the labels of dryer sheets, clothes softener liquids, antistatic sprays and synthetic detergents (see the following). They may be listed as cationic (CAT-eye-ON-ic), anionic (AN-eye-ON-ic) or nonionic (NON-eyeON-ic). The charged ends of the molecules can be either positively charged (cationic) or negatively charged (anionic). The nonionic surfactant molecules aren’t charged at all, so they may be good at clothes softening but are of no use for killing static cling.
A widely used cationic surfactant is dimethyl ditallow ammonium chloride, and a common nonionic surfactant is polyethylene glycol monostearate.
Laundry detergents (see the following) commonly contain the anionic surfactant sodium alkylbenzenesulfonate.
As if you cared, right? But now you can have fun decoding the fine-print ingredient lists on all those product labels. Run right down to the laundry and check them out.