Effects of Curing Conditions and Formulations on Residual Monomer Contents and Temperature Increase of a Model UV Gel Nail Formulation

Abstract

Recently, the application of ultraviolet (UV) curable monomers to human nails, (also known as UV gel nails) has become a popular decoration technique for women’s nails. However, the unreacted layer, the depletion of residual monomers from the cured UV gel nails, which can cause allergy and asthma, and the increase in temperature during curing process, are major concerns. In this study, the thickness of the unreacted layer, the increase in temperature, and the residual contents in cured film of UV gel nail treatment were measured for the first time. The results of this study indicated that the thickness of unreacted layer was not affected by the cast thickness; however, the intensity of UV light and the photoinitiator concentration had significant effect on the thickness of the unreacted layer. To reduce the thickness of the unreacted layer, the intensity of the UV light and the photoinitiator concentration should be increased. However, the maximum temperature observed during the curing of UV gel nails increases with an increase in the intensity of the UV light and the photoinitiator concentration. A suitable cast thickness range (21 ~ 150 μm), which resulted in the formation of a cured film and without producing temperatures that exceed that of the human body, was identified. The mass fraction of the residuals in the cured layer decreased with an increase in the exposure time, the UV intensity, and the photoinitiator concentration.