It’s a fingernail biting problem. You would like to have nice, long, shapely nails but yours just won’t grow properly. Time for a little chemical help. You know you can avail yourself of the latest acrylic technology at your local nail salon, but you have a lingering concern about safety. You’ve heard about the nasty things that methylmethacrylate can do. Redness, swelling, itching, blisters, lifting of the nail from the nailbed, irritation of eyes, nose and the bronchial tract. Who wants to take a chance with wicked things like that? Nobody. Certainly not the Canadian or the U.S. governments. That’s why methylmethacrylate is banned from use in sculptured nail products.
But your salon advertises sculptured acrylic nails! Are they defying the law? No. Not all acrylics are created equal. They’re not using methylmethacrylate, they’re using ethylmethacrylate. May not sound very different, but the extra carbon atom in this compound’s molecular structure makes a huge difference in terms of its toxicity. Ethylmethacrylate doesn’t have the same potential for skin or respiratory irritation as methylmethacrylate. But what do these chemicals do anyway?
Sculptured nails are distinct from glue-on nails, which have their own issues. The glue-on nails are made of polymethylmethacrylate, a plastic that commonly goes by the name of Plexiglass. This material is inert and doesn’t cause problems, but the glue with which it is stuck on, a cyanoacrylate, can cause irritation in people who have become sensitized to it. Sculptured nails are also made of polymethylmethacrylate, but the formation of the plastic actually takes place on the nail. A flexible template is inserted under the natural nail plate and the elongated sculptured nail is then built on top of the nail and the template extension. The process involves mixing two components, one a powder, the other a liquid, and applying the mixture to the nail with a brush in layers. In minutes the plastic hardens, it can be sanded and then covered with nail polish.
Now for the interesting chemistry that’s involved here. The powder is polymethylmethacrylate, a polymer that is formed by joining methylmethacrylate molecules into a long chain. The role of the liquid with which the powder is mixed is to cross-link the long polymethylmethacrylate chains. Sort of like using rungs to make a ladder. The liquid contains individual molecules of ethylmethacrylate. When mixed with the powder, and prompted by an “initiator,” also contained in the powder, the ethylmethacrylate molecules join together to form a chain that ties together the polymethylmethacrylate chains. The result is a hard plastic. Before it was banned in 2003, methylmethacrylate was used as the cross-linking agent and it created numerous problems. Today people still have a concern about acrylic sculpted nails because few appreciate the difference between the terms ethyl and methyl. But when it comes to chemistry, the difference between that “e” and “m” is huge.