Title
Hydrophobic functionalization of cellulosic substrates using atmospheric pressure plasma
Authors
KARTICK K. SAMANTA T. N. GAYATRI S. SAXENA S. BASAK S. K. CHATTOPADHYAY A. ARPUTHARAJ and V. PRASAD

Received February 16, 2014
Published Volume 50 Issue 7-8 July-August
Keywords cellulosic textile, fluorocarbon, hydrophobic, nano-scale surface modification, plasma

Abstract
In the present study, without using water as a processing medium, a hydrophilic cotton (cellulosic) textile was plasma treated in an indigenously developed atmospheric pressure plasma reactor in the presence of helium-fluorocarbon (He FC) gases, for imparting hydrophobic functionality to the treated textile. The optical emission spectra (OES) showed the fragmentation of fluorocarbon molecule with atomic lines of F at 429 nm, 357 nm, 341 nm, 325 nm and –CF2 line at 318 nm. After the plasma treatment, the hydrophilic cotton turned into a highly hydrophobic one, and as a result, a water droplet of 37 µl was not absorbed by the fabric even after 60 min, in contrast to the untreated fabric, which absorbed the water droplet within 0.05 min. The applied finish was found to be durable to soap washing. The ATR FTIR analysis showed the presence of various -CFx molecules in the plasma treated sample and about 4.2% fluorine atom was detected on the surface of the plasma treated sample by EDX analysis. The secondary ion mass spectrometry (SIMS) analysis showed the presence of a strong molecular peak of F− at 19 amu, in addition to significant decreases in O− and OH− molecular peaks at 16 and 17 amu, respectively, in the plasma treated sample. Both scanning electron microscope (SEM) images (physical) and SIMS chemical images (molecular) have ruled out any blockage of inter-fibre spacing inside the fabric structure, confirming this as a nano-scale surface modification of textiles. It is inferred that the hydrophilic cotton cellulose has turned into a hydrophobic one after the plasma treatment, primarily due to the incorporation of various fluorocarbon and hydrocarbon molecules in the cellulose, besides the removal of a large number of hydroxyl groups from it.