Technical Article!

Technical Article


The objective of this research was the development of anti-UV properties polyamide 6.6 and wool fabrics through dyeing with aqueous extract obtained from teak leaves (Tectona grandis). The extract was obtained at different temperatures in order to evaluate the influence of this variable on the dye extraction efficiency. The dyeing was optimized whereas the influence of the most important variables of the process, namely temperature and pH. The highest extraction efficiency was reached at 100 °C. It was found this temperature and pH 5 (polyamide) and pH 3 (wool) are the optimized conditions that produced the best colour strength results. The UV Protection Factor (UPF) of the dyed fabrics presented a significant increase after the dyeing process. The washing and friction properties were also evaluated.


A considerable challenge for the textile industry is the production of multifunctional fabrics from raw materials and procedures with low environmental impact. In this regard, some natural dyes, besides mainly have dye properties, can offer others specific properties such as UV protection (Silva et al. 2018).
Dyed fabrics have a higher UV protection than non-dyed fabrics, increasing according a linear relationship to dye concentration. Usually light colors reflect solar radiation better than dark colors (Driscoll, 2000). The fabric color, its construction and chemical composition are factor that influence the UV protection (Grifoni et al. 2011). 
The Teak (Tectona grandis) is an Asian native plant, and can also be found in Brazil. This natural dye is extracted from the dried leaves. The main compounds present in the teak extract are tannins, coumarins and amino acids (Ferreira et al. 2018).
Dye extract from the teak dried leaves was obtained by aqueous extraction. Woven wool fabric (150 GSM) and polyamide were used for dyeing process. The dyeing process was performed at different temperatures and pH in a Kimak AT1-SW. UPF index was measured using an SDL-M350 spectrophotometer, according to the technical procedures in AS/NZS 4399: 1996.
The color parameters were measured by spectroscopy in the visible range, by analyzing the CIELab colorimetric coordinates and the color intensity (K/S). The washing fastness tests were performed according to the standard procedure ISO 105-C06:2010 (Cycle A1S). The rubbing fastness was carried out according to ISO 105-X12:2016.


The UV-Vis spectra of teak leaves extracts at different temperatures extraction are shown in Figure 1.
It is possible to notice that the increment of extraction temperature led to an increase in the absorbance of the aqueous extract. In this research, the extraction temperature of 100º C show the higher absorbance value. 
The increase in temperature leads a higher concentration of compounds in solution and, probably, a greater efficiency of extraction process.
The UV-Vis spectra also revealed that the extract show absorbing radiation ability of in UV-C (100-280 nm), UV-B (280-315 nm) and UV-A (315-400 nm) range. Therefore is predictable that the fibers dyed with the teak extract acquire an increased capacity for absorb UV radiation, making them more suitable for anti-UV textile applications.

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