of the UV cure light technology a study [27] showed that the worst-case scenario was exposure to UV-A light source for 36 minutes per day which was far below the occupational exposure limits for UV radiation. The report showed that normal use of a UV nail gel lamp only exposed the consumer to 0.5% to 2.2% of the monthly allowable exposure limit to UV energy. These energy levels were 0.30 to 1.676 µW/cm2. The UV cure light units operated within the UV-A range of 350 to 400nm [27]. The formulation of the UV nail gel as shown in the previous section contains (meth) acrylate monomers. A recent study [28] found concerns with allergic contact dermatitis (ACD) due to the use of (meth) acrylate monomers in the nail gel formulations. They found that 241 patients tested over a three-year period had a positive patch reaction to the acrylate resin. In light of some of these ACD issues, the British Contact Dermatitis standard series of concerned chemicals has just added 2-hydroxyethyl methacrylate to this series. In addition, the studies found that both local and distant ACD can occur that would result in hyperkeratosis and fissuring of the finger pulp, lichenoid or psoriasiform eruptions, paronychia and nail dystrophy. Concerns were also shown that evaporation of the nail gel results in airborne ACD that could result in issues for the face, neck and ears [28].
3.13 Prospects on UV Nail Gels
Nail polishes were used in the US by 117 million Americans in 2016 and is expected to reach 122 million by the end of 2020 [17]. The global UV nail gel market is expected to be worth $59.31M in 2020 with a CAGR of 6.5% according to Markets and Markets research firm. North America accounted for 53% of the global market as of 2014. Methacrylated oligomers and methacrylated monomers account for 95% market share with 5% for the acrylated oligomers and acrylated monomers [1].
With the UV cure nail gel industry having its roots in the dental industry of the 1950s through the 1970s, this technology became successful in the late 1990s [29]. At the same time the industrial UV cure coatings market was also developing low energy cure technology for the automotive and aerospace industries. This forced the suppliers of the oligomers, monomers, photoinitiators and UV light sources to invest in developing technology that would cure with low level UV-A light sources. The biggest issue that the technology faced was oxygen inhibition. It is interesting to note that the industrial and nail gel markets both benefited from these new developments. With UV light sources transitioning from GA-FL to the LED, the technologies for both markets have taken a significant leap.
Today’s UV nail gel market will continue to grow and has some unique potential for delivering anti-onychomycotic drugs for the elimination of toenail fungus in the toenail plate.
However, concerns over the industrial hygiene issues for the chemistries being used will continue to plague this growing market for the consumer and the UV nail gel technician. In addition, there are industrial hygiene concerns with the UV light sources that cure the UV nail gel whether it is from the FL-GA or LED UV units.
3.14 Summary
The UV nail gel technology has its roots in the UV cure dental restoration and industrial coatings application areas. The uniqueness of the UV chemistry allows the UV nail gel product the ability to cure the UV nail gel products in minutes vs hours for the conventional nail polish lacquer. In addition, the crosslinking of the UV nail gel results in a coating that will last multiple weeks vs. days for the traditional nail polish lacquer. UV cure light sources have evolved since the introduction of the UV nail gel product that used the GA-FL units which are now being displaced with the newer UV LED technology. Oligomeric, monomeric and PI technology also needed to be developed that was able to override the oxygen inhibition and the use of pigmentation for the UV nail gel technology. Initial introduction of UV nail gel technology was centered around the 100% solids oligomer and monomer technology but has now seen newer introductions of water-based UV cure polyurethane dispersions. In addition, bio-based UV nail gel technology has seen introduction of 100% solids and UV cure polyurethane dispersions.
As with any coating’s technology, the UV nail gel technology also needed to understand surface free energy, adhesion, mechanical properties and removal techniques. Alternative use for the UV nail gel technology is as a solution to remedy toe-nail fungus.UV cured nail gel safety has also become an issue. Testing of the UV cure light sources, oligomers, monomers, PIs and removal techniques of the cured coating have been investigated and continue to be investigated especially as newer products are introduced.
The UV cured nail gel technology is unique and has seen a rapid growth in the nail polish marketplace.
Acknowledgements
We would like to thank Kevin Clouser for helping us edit the chapter. We would also like to thank Mary Anne Tolbart for editing the chapter and arranging the text to fit perfectly within the tables.
Michael J. Dvorchak would like to express special thanks to his wife of 47 years for supporting him in all those new adventures that Dvorchak Enterprises LLC has embarked on over the last 5 years.
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