Effect of SiO2 and TiO2 Nanoparticles on the Performance of UV Visible Fluorescent Coatings

Abstract

In the present research, the properties of ultraviolet (UV) visible (daylight invisible) fluorescent coatings modified by the addition of SiO2 and TiO2 nanoparticles were studied. Structural, surface, and mechanical properties and changes in the coatings caused by accelerated ageing were analyzed. The results showed that the addition of nanoparticles caused the changes in unaged and aged printed coatings. Reflectance measurements of modified coatings showed that addition of TiO2 nanoparticles improved the visual effect of the unaged coatings. Furthermore, results have shown that the addition of SiO2 did not diminish the reflectance of the modified coatings after ageing. The results of roughness measurements showed that the addition of SiO2 decreased roughness after the ageing process, probably due to the degradation process indicated by Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy. The roughness of the coatings with TiO2 nanoparticles was increased after the ageing on the samples with higher concentrations of TiO2 due to the agglomerates of plastisol formed on the surface of the coatings, visible in SEM images. Surface analysis of coatings showed that TiO2 caused an increase in the polarity of the surface coatings. Results of the bending stiffness showed that the addition of the nanoparticles to the coating, especially of SiO2, significantly improved the bending stiffness of the unaged samples.

Properties and Colorimetric Performance of Screen-Printed Thermochromic/UV-Visible Fluorescent Hybrid Ink Systems

“…This can be attributed to the highest measured roughness parameters (Table 4). The results of SFE calculations are in the accordance with SFE values of TLC ink printed on papers, as well as with the hydrophobicity of the UVF ink [26,30]. In general, surfaces of hybrid ink systems printed on CB paper presented higher SFE than prints on UT paper.…”

“…TLC ink was printed on substrate and after the drying, the TLC printed layer was covered with a layer of UVF ink. UVF ink was prepared before the printing process, by mixing the UVF pigment in the transparent base in 3% mass concentration [26]. The designation of this system is UVF on TLC.…”

“…For this system, UVF pigment was directly mixed into the TLC ink (no transparent base was used). The mass concentration of UVF red pigment was 3% according to the previously published research [26]. The designation of this system is UVFp in TLC.…”

“…The results of spectral reflectance measurements of the printed UVF ink and hybrid ink systems are presented in Figure 4a,b. Peaks detected in the range of 580-660 nm correspond to the spectral reflectance of the used UVF red, Eu 3+ -based pigment [26].…”

“…Results of that research showed that the addition of nanoparticles does not cause any significant change in the visibility of the fluorescence effect. The research also addressed the influence of the aging process on the stability of fluorescent prints and concluded that the addition of nanoparticles could have a positive impact on the fading of the UVF prints and on the observed chemical and mechanical characteristics of printed coatings [26]. To observe the influence of the addition of SiO 2 and TiO 2 nanoparticles in the varnish used in flexography, the fluorescent varnish was printed on polyester substrate, woodfree uncoated paper, and 100% recycled packaging paper [27,28].…”