The Science of Nails

Chemist's Corner: Acrylics

Let's go back to the basics on acrylics. 

Applied to a natural nail as a protective overlay, over a nail tip, or even sculpted to extend the natural nail, acrylic nail enhancements always start with a combination of monomer (liquid) and polymer (powder). Today’s acrylic powders are offered in a variety of colors allowing nail techs to get creative with nail enhancements outside of the classic French tip. But before you apply a customizable set on your client’s nails, let’s go back to the basics. Dr. Paul Bryson, former research and development director and now director of regulatory compliance for OPI, reminds you why understanding the science behind the products you’re using can help troubleshoot common application problems.

NAILS: What is the chemical makeup of acrylics?
Dr. Paul Bryson: The liquids are made of liquid acrylic monomers (small molecules that can react to make long chains), plus a catalyst. The powders are made of acrylic polymers (large molecules composed of acrylic monomers that are bound together in chains or networks), plus an initiator.

NAILS: What exactly happens when the monomer and the polymer get together?
PB: When powder and liquid are mixed, the catalyst and initiator react, causing a chemical reaction called “polymerization.” Polymerization is the linking up of the small liquid monomer molecules into long chains and networks, which in the end, are solid. Think of the catalyst and initiator as analogous to a match and a striking board—alone, nothing happens, but together, they spark the reaction.

NAILS: Before they were liquid and powder, can you describe how the products were made?
PB: The powder is polymerized at the factory; the starting material is liquid monomer. So it’s almost the same process as the final curing of the nail, except that the powder is polymerized in a solution so that it comes out as small spheres.

NAILS: Why is a proper mix ratio such an important part of acrylic application?
PB: It’s important for work properties. And also, you need to get the right catalyst and initiator ratio so the product will fully cure.

NAILS: What determines the set time? Why do nail techs have to work quickly and efficiently when applying acrylics? What role does the catalyst in the liquid play in this process?
PB: Set time is determined by how fast the product polymerizes, which in turn is set by fine tuning the catalyst and initiator levels. Once the catalyst and initiator are mixed, the monomer starts to polymerize and harden, so you don’t have much time.

NAILS: Are there any types of ingredients that cause premature hardening?
PB: It’s actually the lack of certain ingredients (inhibitors) that causes premature hardening. Inhibitors need to be added to all acrylic monomers to prevent premature curing. If these become depleted due to heat or age, the monomer can polymerize (harden) prematurely.

NAILS: When it comes to removing acrylics, once a nail tech files down the enhancement and soaks it in acetone, how does this process help the solvent?
PB: The more material can be filed off mechanically, the less has to be acetone soaked. It’s really that simple. Just don’t file too far and damage the natural nail.

NAILS: What causes acrylics to release vapor (odor)?
PB: Small molecules are by nature rather volatile. You’ll notice the liquid monomers have a much stronger scent than the powder (polymers).

NAILS: Is there a chemical difference between odorless/low-odor acrylics?
PB: Low-odor monomers are made from larger molecules, which are a little less volatile.

Common ingredients:

> Liquid: Ethyl methacrylate, better known as EMA (the main ingredient), hydroxyethyl methacrylate (HEMA) and hydroxypropyl methacrylate (which increase adhesion), various dimethacrylates (which are crosslinkers), plus a catalyst, usually dimethyltolylamine.

> Powder: Acrylates copolymer (usually a combo of EMA and methyl methacrylate (MMA) monomers are used. Note that MMA is harmless after polymerizing, the powders contain inert poly-MMA, or PMMA). Plus the initiator, benzoyl peroxide.

You might also like:

Chemist's Corner: Nail Strengthener 

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