Surface modification of anhydrous borax powders with stearic acid via mechanical dry powder coating

Abstract

Surface modification of anhydrous borax powders with stearic acid in the laboratoryscale planetary ball mill via mechanical dry powder coating approach was investigated.The alteration of hydrophilic surface properties of anhydrous borax with stearic acidwas optimized by modifier amount and activation time. The cohesion mechanisms ofpowders, which processed at conditions of 0.5, 1 and 2 wt.% stearic acid amount withthe function of 30, 60 and 120 minute activation time, were evaluated in terms of thesolubility test, contact angle measurements, particle size distributions, and scanningelectron microscopy (SEM) analysis. Results indicate that anhydrous borax surface couldbe switched from hydrophilic to hydrophobic with changing contact angle from wetting(17o) to non-wetting (99o). Water-insoluble amount of anhydrous borax powders, as acoating efficiency indicator, was increased from 73% to 91% by coating with 1 wt.%stearic acid for 60 min. Furthermore, SEM analysis results demonstrate that stearic acidwas discretely coated over the anhydrous borax surface. As a conclusion, an effectivemechanical dry coating processing by a one-step coating approach could be applied toobtain a modified anhydrous borax surface, which offers controlled solubility behaviour inwater-based suspensions.