Enhancement of Polymer Powder Wettability by Using Surface Dielectric Barrier Discharge

The surface of 180- $\mu \text{m}$ polyethylene (PE) and 200-nm polytetrafluoroethylene (PTFE) powders are hydrophilized by using surface dielectric barrier discharge (sDBD) applied to a batch of 20 g for both cases. On the sDBD electrode, charged particles by plasma generation are able to diffuse onto the power surface through small voids. In order to know the level of hydrophilic treatment on the powder, absorption tests by using droplet was carried out. This principle is based on the fact that the inner gap between powders are small enough that a liquid with a certain surface tension is absorbed or formed on powder layer when dropped on the powder surface. The minimum isopropyl alcohol (IPA) concentration absorbed into the powder was measured by an aqueous solution with a mixture of IPA and D.I water. By lowering the IPA concentration, improvements in the hydrophilicity were obtained. The concentration of IPA before treatment of PE powder was 15% and decreased to 3% after treatment. In the case of PTFE, IPA concentration decreased slightly from 39% to 30% after the treatment. Also, the surface treated PE and PTFE displays a significant difference in the degree of dispersion in water and n-methyl pyrollidone solvent. In the field-emission scanning electron microscope analysis, the morphology of the treated surface was clean. From composition of the surface by X-ray photoelectron spectroscopy, when the untreated sample is 100% C–H, the plasma treated PE shows 82.48% C–H, and 17.52% C–O. A partial change in the C–F bond is shown for PTFE.