(443e) Understanding the Surface Chemistry, Surface Roughness and Wettability of Argon Plasma Treated Cornstarch Powder

The glow discharge plasma of inert argon (Ar) gas was used to alter the surface of corn starch powder (17 micron particle size) in pellet forms at optimized pressure and voltage for different time (5, 10, 15, 20, 25, and 30 min). The effect of argon plasma on the wettability, surface morphology and surface chemistry of treated cornstarch pellets were studied by static contact angle measurement (sessile drop method), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Surface Energy respectively. The contact angle (CA) measurement shows that contact angle changes from 48 ÌŠ (hydrophilic) to 22 ÌŠ (more hydrophilic) with the increase in plasma exposure time. The corresponding total surface energy increases from 43 mJ/m² to 49 mJ/m². The SEM and AFM data reveals that the argon plasma treatment on cornstarch pellets resulted in increased surface roughness (16 nm to 32 nm) due to intense ion bombardment at the surface. The increase in total surface energy is attributed to the functionalization of the corn starch pellet surface with the hydrophilic groups (change in polar component of surface energy) and the increase in surface roughness of pellets. It was demonstrated that the Wenzel wetting regime is inherent for corn starch pellet (CA< 90ÌŠ) even after treating with argon plasma. The increase in spreading coefficient and work of adhesion justifies the droplet state in Wenzel regime. The argon plasma treatment and subsequent atmosphere exposure lead to the incorporation of more oxygen functionalization at the surface. The result shows that the change in surface roughness and surface energy enhances the wettability of corn starch. This improved wetting nature is implicated with roughness created by Ar plasma and a corresponding change in surface energetics.