Guwahati: The demand for natural dyes has grown rapidly in recent years as consumers and companies look for sustainable, non-toxic alternatives to synthetic dyes, which often contain harmful chemicals.
Natural dyes, however, have faced challenges in achieving the color vibrancy, fastness, and durability that synthetic dyes offer.
Now, a new study by researchers from Assam has developed a sustainable method to dye mulberry silk using extracts from discarded teak leaves. The team was led by Dr. Parikshit Gogoi, an Assistant Professor of Chemistry at Nowgong College (Autonomous). The team included Dr. Rinku Moni Kalita, Priyanga Manjuri Bhuyan, Dr. Barnali Sarma, and Dr. Swapnali Hazarika. Shristirupa Borah and Priyanga Manjuri Bhuyan are PhD scholars under Dr. Gogoi, with Shristirupa Borah solely conducting the experiments. The study was published in Fibers and Polymers Journals.
The team collected teak leaves from a plantation in Nagaon and developed a novel extraction method using a solvent system of methanol, water, hydrochloric acid (HCl), and sodium carbonate (Na2CO3).
This system was selected after careful optimization to maximize extraction of the leaves’ functional compounds—primarily polyphenols and flavonoids. These compounds are antioxidants and are responsible for both the color and protective qualities of the dyed fabric.
To achieve optimal results, the researchers prepared the leaves by first deactivating natural enzymes at 60°C and then oven-drying them at 80°C for 15 hours. The dried leaves were then ground into powder and processed in methanol and water, with HCl and Na2CO3 added to maintain the pH of the solution.
At a temperature of 80°C and with a dyeing time of 45 minutes, this process yielded the highest color depth (K/S value of 48.338) and UV-protective properties (UPF of 56.10) on the silk fabric. These levels of color strength and UV protection are comparable to those achieved with synthetic dyes, marking a significant accomplishment in the natural dye sector.
The study also explored the use of metal mordants, substances that help fix dye to fabric, to enhance the durability of the color. Alum was found to be the most effective mordant, helping the silk retain its vibrant color even after washing, light exposure, and abrasion.
This mordant enhanced the fabric’s color fastness ratings to levels of 4–5, indicating the dye’s strong resistance to fading and wear. This is a crucial factor for textile applications, as one of the primary drawbacks of many natural dyes is their tendency to fade over time.
Beyond color vibrancy and durability, the dyed silk also demonstrated impressive functional properties, thanks to the bioactive compounds in teak leaves. The polyphenols and flavonoids extracted from the leaves exhibited strong antioxidant and antibacterial properties. The dyed silk showed significant antimicrobial activity against Staphylococcus epidermis, a bacterium that can cause skin irritation.
This suggests that textiles dyed with teak extracts could be particularly beneficial for products such as scarves, masks, and other items that come into close contact with the skin, as they help inhibit bacterial growth and reduce the risk of infections.
The ultraviolet protection factor (UPF) was another noteworthy benefit. Due to the molecular structure of polyphenols and flavonoids, which absorb and dissipate UV rays, the dyed silk fabric demonstrated substantial UV protection. This feature is increasingly valuable in textiles, as UV radiation can not only damage fabrics but also pose health risks to wearers.
The process used by the researchers aligns with the principles of green chemistry. By utilizing a renewable resource—teak leaves that are usually discarded as waste—they developed a dye solution that minimizes environmental impact. Teak leaves have long been used in traditional practices for coloring and cooking, but their application in textiles has not been fully explored until now.
The study provides a potential pathway for scaling this dyeing method to an industrial level, which could bring sustainable dyeing practices to a much wider audience.
With their findings, the team has provided a model for environmentally friendly textile production that could reduce dependence on synthetic dyes. As sustainability becomes a priority across industries, this type of innovation highlights how plant-based solutions can be both functional and protective.
The team envisions future applications beyond silk, as teak leaf extracts could be used on other natural fibers, potentially expanding the reach of plant-based dyes in the global market.
The pioneering work could signal a shift for the textile industry, providing eco-conscious consumers with high-quality, plant-dyed fabrics that blend beauty, safety, and sustainability in a single product.
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