Surface modification of fine powders using plasma treatment

Abstract

Plasma-surface modification (PSM) is an effective and economical surface treatment technique for many materials. In this work, changes in surface properties of 17 µm corn starch powder due plasma exposure are studied. The inert Argon gas plasma is used to alter the surface of corn starch in both powder and pellet forms at optimized pressure and voltage for 5 min, 10 min and 20 min. The surface level changes in morphology and surface roughness were measured using: Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) respectively. The changes in surface energy of powders were easured using surface energy analyser (SEA) at infinite dilution. The surface level changes in morphology, surface roughness and surface energy due to plasma was tracked through the changes in wetting behaviour of the powder through contact angle measurement using sessile drop method in the pellet form. The SEM and AFM results show that corn starch in powder and pellet form is etched and their surfaces becomes rougher than original as received corn starch. Moreover, the roughness increased with increasing the etching time. The result shows that the change in surface roughness and energy enhances the wettability of corn starch. The study shows that longer the plasma exposure, larger is the reduction in the contact angle indicating improved wetting characteristics of the powder. This improved nature is implicated with roughness created by plasma and corresponding change in surface energetics.