In this study, Nylon 6 nanofiber were prepared by needle-less wire electrospinning technique. Since, the fiber diameter determines the porosity, filtration efficiency, and mechanical properties of electrospun nanofiber mat, Central Composite Design (CCD) and Response Surface Methodology have been employed to design the experiments and evaluate the interactive effects of the operating variables such as concentration of the polymeric solution, the distance between two electrodes, applied voltage, and relative humidity (RH%) on the diameter of the Nylon 6 nanofiber. With this connection, an objective of this study was to find out the most influential variables for the finest nanofiber diameter during the spinning with wire type electrode to make the highest possible effective face mask without the addition of any functional additives in it. The overall results show that the combined effect of 12% polymer concentration, 65% RH, 155 mm distance between two electrodes, and 40 kV applied positive voltage have the strongest surface response and are the most significant than the other interactive effects. The Pareto chart illustrates the order of significance affecting the Nylon 6 nanofiber diameter in the order of concentration of the polymeric solution, RH%, the distance between electrodes, and applied positive voltage. Further, bacterial filtration efficiency% of the control sample and five-layer facemask incorporated with optimized nanofiber membrane was found to be 87.4% and 97.5%, respectively, against Staphylococcus Aureus ATCC 6538 bacteria.

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Purpose The purpose of this study is to check the effectivity of plasma in the natural dyeing of polyester fabric using four natural dyes – Turkey red, Lac, Turmeric and Catechu using plasma and alum mordant. The surface modification on the polyester fabric by plasma along with the use of benign mordant alum is studied. The enhancement of dyeability in polyester fabric with natural dyes is the main focus. Due to surface modification, the wettability increases, which leads to better dye uptake. Better dye uptake and better dye adherence are the main objectives. Design/methodology/approach Plasma-mediated natural dyeing is the main design of this research work. The effect of plasma treatment on surface modification of synthetic fabric polyester and its subsequent effects on their dyeing with different natural dyes, namely, Turkey red, Lac, Turmeric and Catechu are studied. The dyeability was further enhanced by the use of alum as mordant. The main focus is on the betterment of natural dyeing of polyester fabric using sustainable natural dyes resources for dyeing and to reduce wastewater contamination from the usage of toxic additive chemicals for cleaner production. Findings Plasma-mediated and alum-mordanted dyeing method facilitated very good dyeability of all the four natural dyes, namely, Turkey red, Lac, Turmeric and Catechu. Color strength (K/S) values and fastness properties of plasma-treated samples were far better than untreated samples. The synergistic effect of plasma and alum mordanting has made natural dyeing of polyester very easy with very good fastness results. Natural dyeing of polyester after 2 min of plasma treatment showed excellent and desirable results. The process is also easy to be adapted by industries. Research limitations/implications As polyester is hydrophobic, natural dyeing of polyester fabric is not very easy, but with plasma-mediated natural dyeing, it becomes a very facile dyeing method; thus, there are no limitations. Use of plasma has reduced the need for any chemical additives which are usually added during the dyeing process. Practical implications This process of natural dyeing of polyester fabric can be scaled up to industrial dyeing with natural dyes. Plasma pretreatment of the fabric followed by premordanting with alum has facilitated the natural dyeing well. Social implications Use of plasma in place of chemical modifiers can be a green and environmentally friendly approach for sustainable coloration of polyester fabric, providing a clean wet processing for textiles dyeing. Originality/value The synergistic effect of plasma-mediated and alum-mordanted natural dyeing of polyester has not been attempted by any researcher. To the best of the authors’ knowledge, this is for the first time that pretreatment with atmospheric plasma followed by alum mordanting of polyester fabric has shown very good dye uptake and fastness properties as the dye molecules could penetrate well after 2 min of the plasma treatment.