Colour analysis of organic synthetic dye coating paint films consisting 4-hydroxycoumarin derivatives after exposed to UV-A

This work investigates the visible optical stability of coating paint film consisting organic synthetic dye, 4-hydroxycoumarin derivatives to the exposure to ultraviolet A (UV-A) light. An azo dye was synthesized by coupling diazonium salt of aniline derivative (obtained by diazonation of 4-chloroaniline in presence of sodium nitrite and hydrochloric acid) with 4-hydroxycoumarin in the presence of sodium hydroxide. The azo dye was mixed with xylene before using it as a pigment in the coating composition. The mixture of poly(methyl methacrylate) (PMMA) and acrylic polyol was used as the coating binder. The synthesized dye and binder were then mixed at specific ratio to form a complete coating solution. Two coating solutions with PMMA having different molecular weights (Mw: 350,000 gmol-1 and Mw: 996,000 gmol-1) were used in this study. Each of them was labelled as 350 K and 996 K indicating its molecular weight. Both mixtures were applied as coating paint films on glass substrates were exposed to UV-A for fast photo-degradation process. The visible optical stability of the coating paint films was measured and recorded at an interval of eight-hours exposure for 35 days using the Commission Internationale de l'Eclairage (CIE) L∗a∗b∗ colour coordinate system. The obtained datas were analysed using standard deviation (STD). In this study, both coating samples showed low standard deviation for hue angle, namely 0.206 for 996 K and 0.258 for 350 K which indicates a high colour stability. However, the 350 K possesses a smaller colour difference (ΔE) of 0.798 compared to 1.418 for 996 K. © 2019 IOP Publishing Ltd

The visible reflectance spectrum stability and water content resistivity of natural dye coating paint film consisting chlorophyll

Purpose: The purpose of this paper is to study the colour stability and water content resistivity of the green colour coating paint film (consisting of chlorophyll) during exposure to ultraviolet A (UV-A). Design/methodology/approach: The natural green dye was prepared by immersing Cassia alata L. leaves in absolute ethanol. The extract was prepared in two batches of dye samples where one of it was a pure dye and the other was added with 3 Wt. % Cu(NO3)2 as an additive. Polymer blend as a binder was prepared by mixing poly(methyl methacrylate) (PMMA) and commercial acrylic polyol. The blended polymer was mixed with the natural dye in a specific ratio and applied as coating paint film on glass panel surfaces. The visible spectrum stability (colour stability) and water content resistivity of the coating paint films during exposure to UV-A were monitored. Findings: Addition of Cu(NO3)2 had improved the colour stability of the coating paint film. Fourier transform infrared spectroscopy analysis showed that both coating paint films do not absorb water and are resistive to water content. Research limitations/implications: The ability of Cu(NO3)2 as an colour stability additive to the natural green dye applied in the coating paint film. Practical implications: The coating paint film developed in this work is suitable to be applied on glass substrates. Originality/value: The colour stability of the coating paint film was analysed by using the reflectance spectrum

The colour stability of natural blue dye extracted from Clitoria ternatea L. in poly(acrylamide-co-acrylic acid) coating film

Purpose: This paper aims to focus on a comparison study of the visible stability of natural blue dye consisting anthocyanin molecules extracted from Clitoria ternatea in coating films. Design/methodology/approach: The coating films were prepared by mixing the blue dye with poly(acrylamide-co-acrylic acid) in three different weight ratios. Samples were coded as 10PBA, 15PBA and 20PBA, where PBA is the abbreviation for poly acrylamide-co-acrylic acid, blue dyes and anthocyanin. The number at the beginning of each code represents the weight percentage of poly(acrylamide-co-acrylic acid) to natural blue dye. The mixtures were applied on separate glass substrates to form coating films. Another set of samples were prepared for the comparison study with a commercial acrylic clear coat (cc) applied on the surface of the 10PBA, 15PBA and 20PBA coating films. These coating films were coded 10PBAcc, 15PBAcc and 20PBAcc. The purpose of the clear coat is to observe how it affects the colour stability of the blue coating films with respect to time. All samples were exposed to the ultraviolet (UV) source, an 18 W Philips TL-D 18w/830 UV fluorescent lamp. The UV lamp was placed 15 cm above the surface of the samples for 35 days. The colour of the coatings was measured using CIE L*a*b* colour space coordinate. Findings: The results obtained show 10PBA and 10PBAcc have the highest colour stability after 35 days of exposure to UV light. The reflectivity of the coating films was also measured during exposure to UV lamp. Reflectivity measurements also showed that 10PBA and 10PBAcc coating films had the highest reflective stabilities. Research limitations/implications: The potential of using natural blue dye consisting anthocyanin in coating film to obtain high colour stability. Practical implications: The coating film developed in this work is suitable to be applied on glass substrates. Originality/value: The application of anthocyanin dye extracted from the Clitoria ternatea L. as a colourant in coating films. © 2019, Emerald Publishing Limited