The dyeing and finishing step represents a clear hotspot in the textile supply chain as the wet processing stages require significant amounts of water, energy, and chemicals. In order to tackle environmental issues, natural dyes are gaining attention from researchers as more sustainable alternatives to synthetic ones. This review discusses the topic of natural dyes, providing a description of their main features and differences compared to synthetic dyes, and encompasses a summary of recent research in the field of natural dyes with specific reference to the following areas of sustainable innovation: extraction techniques, the preparation of substrates, the mordanting process, and the dyeing process. The literature review showed that promising new technologies and techniques have been successfully employed to improve the performance and sustainability of natural dyeing processes, but several limitations such as the poor fastness properties of natural dyes, their low affinity with textiles substrates, difficulties in the reproducibility of shades, as well as other factors such as cost-effectiveness considerations, still prevent industry from adopting natural dyes on a larger scale and will require further research in order to expand their use beyond niche applications.

The objective of this work was to assess the possibility of dyeing a substrate composed of non-textile industrial hemp using natural dyes from common madder (Rubia Tinctorum L.) and calendula (Calendula Officialis) and tannin and alum as mordants. The substrate used for the dyeing had a 25/75 hemp/cotton composition. The hemp raw material is an agricultural by-product that was subjected to mechanical and chemical treatments in order to cottonize the fibers, blend them with cotton, and thus obtain first 40-tex open-end yarns and then a knitted fabric. The latter was subjected to different dyeing conditions by varying the dye, mordant, and method for its application, type of water, and rinsing after dyeing. Measurements of the difference (ΔE) and intensity (K/S) of color and fastness to washing and rubbing were carried out. The results showed that dyeing of a non-textile residual hemp substrate is possible, and that calendula is a good option for dyeing it with tap water, tannin-alum set in a meta-mordanting process, and rinsing after 24 h. In this way, a contribution has been made to the circular economy of the textile industry through the use of more sustainable sources and products.

The inclusion of particles in a polymeric substrate to achieve certain properties is a well-known practice. In the case of textile substrates, this practice may deeply affect the structure of the produced yarns, as even a filament with no textile applications can be obtained. In this manuscript, titanium dioxide (TiO₂) particles were incorporated into polyester (PET) chips and the influence of these fillers on the properties of yarn and fabric, and the ultraviolet protection factor (UPF) was assessed. For this purpose, rutile and anatase crystalline forms of TiO₂, as well as the size of the particles, were evaluated. Moreover, parameters such as mechanical properties, orientation of the macromolecules and thermal behavior were analyzed to ensure that the textile grade is maintained throughout the production process. The results showed that the inclusion of micro- and nanoparticles of TiO₂ decreases the molecular weight and tenacity of PET. Also, although orientation and crystallinity varied during the textile process, the resulting heatset fabrics did not present important differences in those parameters. Finally, the attainment of textile-grade PET-TiO₂ fabrics with UPF indexes of 50+ with both rutile and anatase and micro- and nano-sized TiO₂ forms was demonstrated.

Hemp (Cannabis sativa L.) is a plant of which, its ease of cultivation, structure and properties, provide it great potential for industrial applications; nevertheless, the unfavorable content of lignin complicates its processing, especially in the textile area. Thus, an appropriate knowledge of the delignification process would lead to treating hemp fibers as cotton fibers. In this work, hemp has been treated with an alkaline liquor [NaOH 1 M] at 110 °C during different times and afterwards, the substrates were chemically characterized in order to determine their lignin content and also analyzed by thermogravimetry (TGA). Through the correlation analysis, the relationship between lignin content, onset temperature of cellulose decomposition and loss of mass at the different decomposition steps were established. A hyperbolic kinetic model to explain the influence of alkaline treatment time on lignin content and also on the loss of mass at the four steps of decomposition of the samples by TGA up to 600 °C has been developed. Although it has been found that the degradation of lignin occurred across the entire temperature range, results have shown that the influence of treatment time has become clearly relevant on lignin content, Step₂ (180.5 °C-273.5 °C) where a fraction of 10 to 16% of lignin was degraded, and Step₃ 273.5 °C-396.5 °C) where cellulose was mainly decomposed and 20% of lignin was also degraded.

Raw hemp fibers are alkaline delignified to evaluate the effect of lignin on the moisture uptake behavior of hemp. Samples are subjected to moisture absorption/desorption isotherms from 5% to 95% relative humidity at three different temperatures (15, 25, and 35°C). The sorption ratio between delignified and untreated hemp is lowered by 25%. Hysteresis makes evident the greater influence of lignin on moisture binding at low relative humidity while at high relative humidity, cellulose plays the most important role. The GAB, Hailwood‐Horrobin and Dent models are fitted to absorption/desorption isotherms. Delignification and temperature decrease the size of the monolayer. The energy constants of the monolayer differ according to the model used. Lignin causes great differences between absorption and desorption. The greater the temperature is, the lower the monolayer energy constant. The energy constants of the multilayer are identical for the three models, showing a greater range of variation in delignified samples than in the untreated samples. Based on primary and secondary energy constants, bonding enthalpies are determined. Estimations in desorption show higher correlation coefficients with the energy constants, which enables to conclude that measures in desorption better explain the effect of delignification on the water uptake behavior of hemp.

Intrinsically colored cotton is crucial for sustainability as it eliminates the need for chemical dyes, reducing water pollution and carbon footprint. It also preserves biodiversity by using fewer pesticides and supports eco-friendly, ethical product creation. This research aims to examine the factors that influence the color change that occurs in naturally colored organic cotton (NaCOC) fabrics when washed under normal household conditions, and it focuses on special detergents designed for people with skin hypersensitivity. The study observes the impact of various washing conditions on the color changes of the fabrics. Specifically, three specific detergents, two types of water (tap and distilled), and three different temperatures (20, 40, and 60 °C) are taken into consideration as variables. By using colorimetric measures and correlating the results with the significant variables of the experimental design, the study evaluates how washing practices affect both the color and the overall integrity of the fabric. The findings demonstrate that the water hardness is the most influential variable when it comes to the color changes in the fabrics. Additionally, higher washing temperatures exacerbate color changes, particularly in hard water conditions. These results provide valuable insights for maintaining the color integrity of NaCOC fabrics during washing.