Waste left over from rice harvests can be turned into a natural dye that colours fabric and shields the wearer from sun damage at the same time, new research has found. The extract, drawn from rice straw pulping liquid, worked across wool, silk and nylon, with a brief surface treatment applied to fabrics beforehand shown to deepen colour and strengthen protective performance considerably.
- The extract produced warm tones ranging from beige to brown across all three fabric types, with colour holding up well against repeated washing and light exposure.
- Fabrics given a surface treatment before dyeing showed stronger, deeper colour and better resistance to both washing and light than those dyed without it.
- Sun protection improved dramatically after dyeing, with surface-treated and dyed wool recording a protection rating nearly 70 times higher than untreated fabric.
- The findings have been reported in 'Eco-friendly development of multifunctional textiles using rice straw extract', published in Scientific Reports.
INSIDE THE RESEARCH: Four researchers from Egypt's National Research Centre examined rice straw extract as a simultaneous dyeing and finishing agent for three fabric types, wool, silk and nylon 6, under varying concentrations, bath acidity levels and temperatures. Fabrics were cleaned before dyeing and tested across a range of conditions to identify the combination that produced the best results.
- Marwa Abou-Taleb, Khlood S. Abdel Zaher, Salwa Mowafi and Galal A. M. Nawwar authored the study, working across the Centre's textile and green chemistry departments.
- The extract came from liquid waste produced when rice straw was broken down using a sodium hydroxide solution and left to cook in sealed bags under natural sunlight for four days.
- A controlled surface treatment was applied to fabric samples before dyeing to test whether it improved how well the extract bonded to each fabric.
- Laboratory analysis identified 16 naturally occurring plant compounds in the extract, with ferulic acid and syringic acid — both common in cereal crop residues — present in the highest amounts.
- Fabric performance was then assessed for colour quality, resistance to washing and light, sun protection, antioxidant benefit, moisture absorption and heat resistance.
THE RESULTS: The best dyeing results came from using the extract at a mid-range concentration, in a mildly acidic bath and at a high temperature, with surface-treated fabrics consistently delivering stronger results than untreated ones across every performance measure tested. Colour quality, sun protection, antioxidant activity and heat resistance all improved when fabrics were surface-treated before dyeing.
- Wool's internal structure became measurably less ordered after dyeing, while nylon 6 became more tightly structured, suggesting the extract formed stronger bonds with the nylon surface.
- Heat resistance improved in both wool and nylon 6 after dyeing, with the researchers suggesting the extract showed potential as a flame-resistant material for both natural and synthetic fabrics.
- The surface treatment dramatically improved how quickly fabrics absorbed water, with treated wool wetting in 90 seconds compared with up to 900 seconds before treatment.
- Sun protection improved across all three fabrics after dyeing, though wool and nylon 6 achieved excellent ratings while silk's protection remained more modest even after surface treatment.
- The researchers recommended dyed fabrics for indoor use only, noting that durability under direct and prolonged sunlight exposure remained a limitation.
- Performance held up well across 20 wash cycles, dropping by no more than 18 per cent, though further work on scalability and durability is needed before industrial adoption.
