The colour stability of natural dye coating films consisting of chlorophyll after exposed to UV-A
Abstract
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.
Keywords
Acknowledgements
The authors would like to express gratitude to the University of Malaya for research grants (RG249-12AFR) and (RP025D-14AFR) provided.
Citation
Usop, R., Abidin, Z.H.Z., Mazni, N.A., Hadi, A.N., Halim, N.A., Taha, R.M., Careem, M.A., Majid, S.R. and Arof, A.K. (2016), "The colour stability of natural dye coating films consisting of chlorophyll after exposed to UV-A", Pigment & Resin Technology, Vol. 45 No. 3, pp. 149-157. https://doi.org/10.1108/PRT-10-2014-0097
Publisher
:Emerald Group Publishing Limited
Copyright © 2016, Emerald Group Publishing Limited