12.2 Chemical Reactions, Polymerization & Adhesion

Chemical Reactions, Polymerization and Adhesion

Ohio State Board Exam Alert: The blueprint lists "Chemical Reactions", "Adhesions" and "Monomer/Polymer" as three separate leaves inside the 10 % Product Knowledge & Chemistry domain. Between them they account for the single largest cluster of chemistry items — and they are the theory behind every enhancement service in the practical.

---

1. Fundamentals of Polymerization Chemistry

Unlike traditional nitrocellulose nail lacquers that dry strictly through physical solvent evaporation, artificial nail enhancements undergo a complex chemical reaction known as polymerization (also referred to as curing or hardening). Trillions of individual, microscopic building-block molecules join end-to-end into immense, three-dimensional entangled polymer chains.

+-------------------------------------------------------------------------+
|                    THE CHEMISTRY OF POLYMERIZATION                      |
+-------------------------------------------------------------------------+
| [ MONOMER LIQUID ]       +   [ POLYMER POWDER ]    +    [ ACTIVATION ]  |
| Single building blocks        Pre-polymerized beads      Catalyst meets |
| Ethyl Methacrylate (EMA)      Contains Initiator (BPO)   Initiator      |
|         \                           /                          |        |
|          \                         /                           v        |
|           =========================                Free Radicals Spark  |
|                       |                            Chain Reaction       |
|                       v                                                 |
|               [ SCULPTED BEAD ]                                         |
|           Cross-linked polymer chains form                              |
|           Exothermic thermal release occurs                             |
|                       |                                                 |
|                       v                                                 |
|       [ RIGID ARTIFICIAL NAIL ENHANCEMENT ]                             |
+-------------------------------------------------------------------------+

Key Chemical Components and Their Functions

• Monomer: The term monomer is derived from the Greek mono (single) and meros (part). A monomer is a single, unlinked chemical unit. Monomer liquid is formulated primarily from methacrylate monomers possessing reactive carbon-carbon double bonds ($C=C$).
• Polymer: Derived from poly (many) and meros (parts). A polymer is a giant macromolecule composed of hundreds of thousands of monomers linked together in repetitive, resilient three-dimensional chains.
• The Initiator (Benzoyl Peroxide - BPO): Polymerization cannot initiate spontaneously at room temperature; it requires an external trigger known as an initiator. In acrylic systems, Benzoyl Peroxide (BPO) is incorporated directly into the polymer powder during manufacturing. BPO remains completely stable until it contacts the monomer liquid.
• The Catalyst: A catalyst is an accelerating chemical additive dissolved directly into the monomer liquid. When the technician saturates the brush in monomer liquid and touches the polymer powder, the liquid catalyst accelerates the rapid decomposition of BPO in the powder, cleaving the initiator molecules into highly energized free radicals.
• The Free Radical Chain Reaction: Each free radical attacks the reactive carbon-carbon double bond of a nearby monomer molecule, opening the bond and capturing an electron. This transforms the attacked monomer into a new free radical, which immediately attacks another neighboring monomer. This self-propagating chain reaction links thousands of monomers into elongated polymer chains within two to three minutes.
• Cross-Linking Monomers: Professional monomer liquids contain specialized cross-linking monomers (such as ethylene glycol dimethacrylate). These molecules have two reactive bonding ends, creating rigid lateral cross-bridges between adjacent polymer chains. Cross-linking dramatically increases impact resistance, surface hardness, and chemical resistance to common household solvents.
• Exothermic Thermal Release: Polymerization is an exothermic reaction, meaning that the formation of chemical bonds releases thermal energy (heat). In a correctly balanced bead, this heat dissipation is gradual and virtually undetectable to the client. However, if an improper mix ratio is used, or if product is applied too thickly over thinned nail plates, the excessive exothermic spike can cause acute discomfort and burn the delicate nail bed.

---

---

2. Adhesion, Adhesives and Primers

The Ohio blueprint lists "Adhesions" as its own chemistry leaf, which tells you the Board expects a technician to explain why product sticks — and why it stops sticking.

Adhesion versus cohesion

• Adhesion is the attraction between two different surfaces — enhancement product to nail plate.
• Cohesion is the attraction of a substance to itself — the internal strength of the cured enhancement.
• An adhesive is a substance that bridges two surfaces and holds them together by causing one to stick to the other.

Adhesion depends on molecular contact. Anything that keeps the two surfaces apart — moisture, oil, dust, product residue, hand cream — prevents that contact. This is why almost every case of lifting traces to preparation rather than to the product.

Why nail plates resist adhesion

The natural nail plate is naturally oily and holds 15 % to 25 % water by weight. Sudoriferous glands are most numerous on the palms and the fingertips, and moisture migrates continuously from the nail bed through the plate. A plate that looks dry is not chemically dry.

The preparation sequence, and what each step does

Time matters here. Dehydrated plates begin re-absorbing moisture within minutes, so product goes on promptly.

Two families of primer

The Ohio practical examination scores this precisely in the sculptured-nail task: "Applies primer only to the natural nail plate." Primer on the tip, the form or the surrounding skin costs points and, in the salon, causes lifting and irritation.

Why enhancements lift, in order of frequency

1. Oil, moisture or lotion left on the plate — poor preparation.
2. Cuticle tissue left on the plate — product bonded to a layer that will shed.
3. Product touching skin or the eponychium — no adhesion to living tissue, so the edge lifts at once and forms a moisture pocket.
4. Wrong mix ratio — a wet bead cures weak and shrinks unevenly.
5. Product applied too thickly at the sidewall or cuticle area, where flexing concentrates stress.
6. Contaminated brush or dappen dish.

A lifted edge is not merely cosmetic. It creates a warm, dark, moist pocket between plate and product — the classic environment for Pseudomonas aeruginosa, which appears as the green-black staining technicians call greenies. The correct response is to remove the enhancement, not to fill over the pocket.