D-phase emulsification of neem oil and its application on cotton and silk using response surface methodology

Abstract

Functionalization of textiles using natural plant-based agents is an emerging strategy to enhance comfort, health benefits, and environmental sustainability. This study investigates the development and application of a neem oil-based emulsion for imparting multifunctional finishes to cotton and silk fabrics. Neem oil, recognized for its potent antibacterial and antifungal activity, was emulsified via D-phase emulsification, optimized using Response Surface Methodology (RSM). Optimal emulsion stability was obtained with 5 % neem oil, 2 % surfactant, and 2 % glycerine. The optimized emulsion was applied onto marigold-dyed cotton and silk fabrics, using the pad–dry–cure method. The finished fabrics demonstrated excellent antibacterial activity, with 99.36 % (S. aureus) and 99.62 % (E. coli) inhibition on cotton, and 99.23 % and 98.32 % inhibition on silk, respectively, before washing. Even after five wash cycles, over 79 % inhibition was retained, confirming the treatment's durability. UV protection improved markedly, with UPF values increasing from 18.75 to 19.85 (cotton) and 22.65 to 25.03 (silk) post-finishing. Tensile strength showed slight reduction (cotton: 10.18 to 9.58 kgf; silk: 9.06 to 8.62 kgf), while hand feel was enhanced from grade 4 to 5. The color strength (K/S) values exhibited only a marginal decline (cotton: 2.8 to 2.6; silk: 3.7 to 3.4), indicating minimal impact on dye depth. This study validates the application of neem oil-based emulsion as a sustainable, durable, and effective bio-finish, imparting antibacterial, UV-protective, and tactile improvements without compromising core fabric properties. The results support its potential for eco-functional textiles in apparel, healthcare, and lifestyle applications.