Purpose This paper aims to study the colour stability of chlorophyll and the effect of copper (II) nitrate – Cu(NO3)2 – as an additive in natural dye coating films after being exposed to ultraviolet-A (UV-A). Design/methodology/approach The natural dye was extracted from the leaves of Cassia alata L. using absolute ethanol as the solvent. The extract was divided into two parts and, one of it was added with 3 wt.% Cu(NO3)2 as an additive. The polymer blend of poly(methyl methacrylate) (PMMA) and acrylic polyol was used as the coating binder. Both parts of the dye with and without additive were mixed with the blended polymer in a specific ratio. The resulted mixtures were applied as coating films on glass substrates. The colour stability of the coating films on exposure to UV-A with the time of exposure was observed with Commission internationale de l’éclairage (CIE) L*a*b* colour coordinates. The hidden power by the means of reflectivity and glossiness of the coatings was also studied. Statistical standard deviation (STD) was used to analyse the data. Findings The test showed that the coating films containing Cu(NO3)2 had smaller colour differences, (ΔE*) indicating higher colour stability. The analysis on hidden power also showed that the coating film with Cu(NO3)2 was 1.6 times more stable than the film without additive. All the measurements in this study were observed within 35 days of duration. Research limitations/implications This paper implies the potential of using natural dye extracted from Cassia alata L. leaves as a stable dye colourant for coating applications. Practical implications The coating film developed in this study is suitable for glass substrate applications. Originality/value A new method of preparing solvent-based coating film from PMMA–acrylic polyol with chlorophyll colourant is introduced in this study.
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
Purpose This paper aims to discuss about the benefits of Cu(NO3)2 applied in coating paint film that consists of plant extract from Cassia Alata. Cu(NO3)2 has been added to the coating paint film as a colour stabilizer and as an antifungal property by forming a zone of inhibition towards fungal growth. Design/methodology/approach The coating paint film resin consists of a mixture of poly (methyl methacrylate) (PMMA) and acrylic polyol. The coating paint film’s performances were observed in terms of visible optical and physical appearance. Findings When exposed to the fungus Trichoderma Sp., a zone of inhibition of 208 mm2 was formed around the coating paint film and therefore it gave the coating paint films an antifungal property. The commission internationale de l’éclairage (CIE) L*a*b* colour coordinate system was used to identify the colour changes in the coating paint film and it was found that the addition of Cu(NO3)2 to the coating paint film has a better colour stability, as it has a lower standard deviation (STD) value of 6.46 than the pure dye coating paint film of 8.95. The gloss of coating paint film with the addition of Cu(NO3)2 was found to be have a more stable gloss based on its smaller STD value at both angles taken at 20° and 60°. Research limitations/implications The Cassia Alata plant has different amount of antifungal properties based on location its growth. Practical implications The coating paint film developed in this study is suitable for indoor applications. Originality/value The plant extract from the Cassia Alata gives the coating paint film an antifungal property.
Purpose-The purpose of this paper is to observe the colour and thermal stability of natural red dye consisting of anthocyanin with addition of different aqueous acids and applied as coating films. Design/methodology/approach-The natural red dye was extracted from Hibiscus sabdariffa L. (roselle) flowers and mixed with 1 per cent hydrochloric acid, 5 per cent acetic acid, 5 per cent citric acid and 5 per cent oxalic acid. All the dye samples were exposed to heat and UV-B to observe the colour stability by calculating the half-life and rate of reaction. In coating film application, each of the dye samples was mixed with 25 wt% of poly(vinyl alcohol) (PVA) and applied on to a glass substrate. The coating samples' colour stability was observed by using CIE L ء a ء b ء colour space coordinates. The coating films' weight loss stability against temperature was observed by using thermogravimetric analysis. Findings-Addition of hydrochloric acid enhances the thermal and UV stability of the anthocyanin natural dye. This can be observed from the calculation of the half-life of the dye. The half-life values for the thermal and UV stability studies were 1,155 hours and 210 hours, respectively. In coating films, the sample with addition of acetic acid showed the highest colour stability with colour difference (⌬E ء) value 8.95. Research limitations/implications-The coating films developed in this work are not suitable to be applied on metal substrates due to the presence of water, which can contribute to the corrosion formation. Practical implications-The coating films developed in this work are suitable for washable coating application. In other words, they are non-permanent coatings applied on a glass substrate. Originality/value-Development of water-based coatings from PVA binder with anthocyanin colourant is introduced in this study.
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.
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