Effect of ammonia on madder-dyed natural protein fiber

An eco-friendly method of extracting alizarin from Rubia tinctorum roots under supercritical carbon dioxide and its application to wool dyeing

Because of its low critical temperature and pressure levels, supercritical carbon dioxide (scCO₂) is the most widely used supercritical fluid in the supercritical fluid extraction (SFE) technique. Alizarin was extracted from madder roots (Rubia tinctorum) using scCO₂ under different conditions of co-solvent ratio (0-50%), temperature (45-95 °C), pressure (150-250 bar), extraction time (15-120 min), and flow rate (5-9 mL/min). Based on alizarin recovery and minimization of environmental risk, the optimum conditions were determined. SFE was optimum at 90% CO₂:10% methanol (Me), 65 °C, 250 bar, 45 min, and 9 mL/min. The alizarin recovery, and its content in R. tinctorum extract (RE) under the optimum conditions were 1.34 g/kg roots, and 6.42%, respectively. Using conventional dyeing methods, wool fabrics were dyed with RE at different concentrations (2-6%). Various types of mordants were also used in the dyeing process, including chemical and bio-mordants. Color and fastness properties of dyed wool fabrics were evaluated based on RE concentration and mordant type. A higher RE concentration and the use of mordants, specifically Punica granatum (P. granatum) peels, increased the color characteristics. RE and dyed fabrics exhibited good antibacterial activity against the tested bacterial strains, especially Pseudomonas aeruginosa and Escherichia coli.

A synergistic combination of shrimp shell derived chitosan polysaccharide with Citrus sinensis peel extract for the development of colourful and bioactive cellulosic textile

Green finishing formulations have established an important place in textile dyeing and finishing industry. The use of plant extracts along with chemical metallic mordants is reported to increase colour values and improve fastness properties. However, metal salts as mordants constantly pose environmental and human health risks. The purpose of this work is to examine and extend the knowledge of natural dyeing technology considering the use of biological macromolecule chitosan (CS) to increase dye uptake, fastness and impart functional properties. The cotton was pre-coated with chitosan using pad-dry method and optimal chitosan concentrations were selected by evaluating the colour spectrometry data in term of CIEL*a*b* values. The chemical nature of the extract was characterized by UV-Vis, Fourier-transform infrared spectroscopy (FT-IR) and Thermogravimetric analysis (TGA) whereas dyed samples were analysed by Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) with mapping analysis, FT-IR, and TGA. Results showed that the aqueous extract of Citrus sinensis peel yielded interestingly shades all lying in yellow- red quadrant of CIELa*b* colour space with acceptable grades of wash and dry-wet fastness properties. This study reveals important information to understand synergism between two natural products in imparting semi durable antioxidant and antibacterial activity against E. coli and S. aureus, and thus offers full potential to be used in natural dyeing technology.

Effect of Nano and Micro Emulsion Silicone Softeners on Properties of Polyester Fibers

The processing of textiles to achieve a particular handle is one of the most important aspects of finishing technology. Softeners improve soft handle, smoothness, elasticity, hydrophilic, antistatic and soil release properties on textiles. Macro and micro sized silicone softeners are commonly used for these purposes but nano silicone is a new class of softener. In this research, polyester fabrics were first scoured with nonionic detergent and then treated with three concentrations of nano and micro silicone softeners in water including 10, 20 and 30 g/L at 30°C for 60 seconds by padding method. The treated fabrics were then dried/cured at 130°C for 40 seconds. The pH was maintained at 5 using acetic acid. Some of the physical and chemical properties of the treated fabric samples were discussed. The drapeability of nano emulsion treated samples was decreased compared with micro emulsion treated ones. Colorimetric properties of softener treated fabrics were evaluated with reflectance spectrophotometer. Scanning electron microscope photographs showed nano silicone particles aggregated on fiber surface. Moisture regain of nano emulsion treated samples was decreased compared with micro emulsion treated due to coating of nano silicone particles.

Textile Softeners on Cotton Dyed with Direct Dyes: Reflectance and Fastness Assessments

In this research, cotton fabrics scoured with nonionic detergent were dyed with four different direct dyes (Thiazole, Disazo, Trisazo and Polyazo). The dyed fabrics were then treated with anionic, cationic, nonionic, micro and macro emulsion silicone softeners. CIELAB color coordinates (L∗, a∗, b∗, C∗ and h) were measured with reflectance spectrophotometer. The lightness (L∗ value) for samples dyed with disazo and polyazo direct dyes (orange and red dyes) showed an increase after treatment with all the mentioned softeners, while it was decreased for thiazole and trisazo dyed fabrics treated with anionic, cationic, micro and macro emulsion silicone softeners. The wash and light fastness properties of samples were measured according to ISO 105-CO5 and Daylight ISO 105-BO1. The washing fastness properties of some direct dyed samples were decreased after treatment with softeners. In the case of light fastness properties, it was decreased for most of the samples.

Zirconium Oxychloride as a Novel Mordant for Natural Dyeing of Wool Yarns

Zirconium oxychloride, a well-known flame retardant, is introduced as a novel mordant for wool dyeing. This has been indicated by mordanting of wool yarns with zirconium oxychloride in different conditions and then dyeing with madder as a famous natural dye. The tenacity, color coordinates, washing, and light fastnesses of the dyed wool confirmed the positive influence of zirconium oxychloride as a useful mordant for wool dyeing with a low impact on the color coordinates. Further, an appropriate washing and light fastness were obtained for the zirconium-oxychloride-mordanted wool yarns. The central composite design (CCD) was used to design the experiments with four variables on the results of tensile strength. Statistical analysis confirmed the optimum conditions obtained through the experimental results.

Surface-enhanced Raman spectroscopy of dyes: from single molecules to the artists' canvas

This perspective presents recent surface-enhanced Raman spectroscopy (SERS) studies of dyes, with applications to the fields of single-molecule spectroscopy and art conservation. First we describe the development and outlook of single-molecule SERS (SMSERS). Rather than providing an exhaustive review of the literature, SMSERS experiments that we consider essential for its future development are emphasized. Shifting from single-molecule to ensemble-averaged experiments, we describe recent efforts toward SERS analysis of colorants in precious artworks. Our intention is to illustrate through these examples that the forward development of SERS is dependent upon both fundamental (e.g., SMSERS) and applied (e.g., on-the-specimen SERS of historical art objects) investigations and that the future of SERS is very bright indeed.