Factors influencing the properties of UV-cured self-matting film

Self-matting film with micro-wrinkles on the surface has gained popularity for its desirable attributes, including low-gloss and a pleasant tactile sensation when in contact with the human skin. This study prepared films with varying thicknesses (hfilm) using UV-curable waterborne polyurethane acrylate resins containing different concentrations of photoinitiator (CPI). The effects of two variables on the acrylate conversion, micromorphology, gloss value, roughness, water contact angle (WCA), and friction behavior of the films were investigated. The findings indicate that, when the CPI remains constant, an increase in hfilm leads to a reduction in both acrylate conversion and gloss value of the film. Moreover, the amplitude (A), wavelength (λ), and A/λ of micro-wrinkles, along with the Ra, increase with hfilm, while WCA remains relatively unaffected. Conversely, maintaining a constant hfilm while increasing CPI results in higher acrylate conversion and gloss value. The A and λ of micro-wrinkles and the Ra decrease, while WCA exhibits a slight decrease. Furthermore, this study investigates the impact of varying oxygen concentrations ([O2]) on the equilibrium state of the polymerization rate and the oxygen inhibition rate. The results demonstrate that decreasing [O2] leads to increased acrylate conversion, reduced A of micro-wrinkles, and a transition from low-gloss to high-gloss film as indicated by gloss value measurements. Nanoindentation tests revealed that as the [O2] decreases from 21 % (air) to 0 %, the hardness of the film increases from 0.13 GPa to 0.23 GPa, while the elastic modulus of the film decreases from 23.23 GPa to 3.53 GPa. The findings provide valuable insights into optimizing the synthesis parameters to achieve desired film characteristics, which are crucial for the development of self-matting films with superior aesthetic and tactile qualities.