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We can now delve into the actual formulation of the so-called 100% solids UV cure oligomers and monomers. The following would be considered a baseline formulation that is pigmented or unpigmented.

From the formulation in Table 3.3 one can see that the (meth)acrylate polymer is used as a high molecular weight material that will free-radically cure within the system. The urethane (meth)acrylate oligomer has high molecular weight and high viscosity and will free-radically cure within the system. The mixtures of hydroxyalkyl (meth) acrylate, cycloalkyl (meth) acrylate and tri((meth)acrylate are all low viscosity and low molecular weight monomers that are used to dilute acrylate oligomers to the ‘use viscosity. These monomers will then all free-radically cure within the nail gel coating. When the PI is subjected to either the UV energy emitted from the GA-FL or LED light source the PI forms free radicals like those shown in Figure 3.14. These free radicals propagate the formation of the cross-linked coating with all of the (meth)acrylate species listed in Table 3.3. The proper PI selection criterion as described earlier will be a PI that is activated within the 320 nm to 420 nm range. This matching of the wavelength to the proper PI also has benefits that when the formulation described in Table 3.3 is pigmented the PI shown in Figure 3.14 will function properly above the absorbance of the colored pigmentation [11].

Table 3.3 UV nail gel formulation from patent WO 2017/217/217983. The base formulation for a so-called 100% solids formulation is based on (Meth) acrylic polymer (monomer), urethane (meth) acrylic oligomer, mixture of hydroxyalkyl (meth) acrylate and cycloalkyl (meth) acrylate, photoinitiator, antioxidant and colorant.

Chemical name	wt %
(Meth)acrylic polymer	50-60
Urethane (meth)acrylate oligomer	25-35
Mixture of hydroxyalky1 (meth)acrylate and cycloalkyl (meth)acrylate	10-15
Tri((meth)acrylate)	1
Photoinitiator	2
Anitoxidant	<1
Colorant	<0.05