Optimization of Atmospheric Plasma Treatment Parameters for Hydrophobic Finishing of Silk Using Box Behnken Design

Abstract

ABSTRACT Plasma treatment of mulberry silk fabric was carried out in an indigenously developed plasma reactor in the mixture of helium (He) and commercial fluorocarbon gas at atmospheric pressure. Optical emission spectra (OES) showed the appearance of major atomic lines of helium at 705 nm, 666 nm, 654 nm, 585 nm, and 726 nm. When fluorocarbon gas was introduced into the plasma zone along with helium, it got fragmented and showed atomic lines of fluorine (F) at 429 nm, 357 nm, 341 nm, 325 nm, and for –CF2 at 318 nm. After He-fluorocarbon plasma treatment, hydrophilic silk fabric turned into hydrophobic. Different important plasma process parameters, i.e. treatment time, helium gas flow and fluorocarbon gas flow were optimized using Box Behnken Design using Design Expert 6.0 software. Scanning electron microscope surface morphology exhibits the deposition of fluorocarbon polymer on the fiber surface without blocking the inter-fiber spacing. Hydrophobic characteristic of plasma-treated samples was evaluated by measuring water absorbency time and contact angle value. The sample could retain the imparted hydrophobic finish till 10 repeated washing cycles.