2.1. Preparation of UV-LED Polyurethane Acrylate

Table 1 lists the sample designation and the formulation of the prepared coating. The coating mixture was prepared by dissolving photoinitiator in the reactive monomers (MMA, 2-EHA, HDFDMA, and TMPTA) for one hour at room temperature. Then, it was added dropwise into a beaker containing oligomer and was stirred for another one hour. The prepared mixture was coated onto a clean glass substrate (10 cm × 5 cm × 0.3 cm) with the thickness of 50 μm using a bar applicator. The wet coating was exposed to the UV irradiation in Hönle UV-LED chamber with 15 cm from the light source.

Composition of the UV-LED curable FPUA.

¹ phr: part per hundred.