Effect of Surface Free Energy on the Flowability of Lactose Powder Treated by PECVD

The surface of microscopic lactose particles was modified by gas phase reactions occurring during a PECVD process to improve the flow behavior of the powder. The particulates were exposed to a capacitively coupled O2/Ar/HMDSO RF discharge in a down stream reactor by varying the gas composition and the RF power. The flowability and the surface free energy of the powders were determined by a ring shear tester and by a tensiometer, respectively. Based thereon, the change in surface free energy was determined not to be the dominating factor for the significantly enhanced flowability of the plasma‐treated powder. Rather, the flowability improvement is supposed to be affected principally by the plasma‐induced change in particle surface roughness.