Modification of Active Carbon by Hydrophobic Plasma Polymers: II Fabric Substrates

Abstract

Active carbon, used in various types of chemical protection devices, can absorb an extremely wide range of hazardous compounds. Unfortunately, this “universal” absorption includes ubiquitous water molecules, which can result in saturation and premature loss of efficacy. The purpose of this work has been to treat active carbon-impregnated fabric with appropriate low-pressure plasmas, so as to render the carbon surface “hydrophobic”, while minimally affecting its ability to absorb toxic gases or vapors (simultated here by CCl4). The best results have been achieved using plasma polymerization of organosilicon (PP-HMDSO) thin films onto the fabric surface: This has been done in a pilot-scale microwave plasma reactor system, designed for treating continuously-moving flexible web materials up to 30 cm in width. Under “optimal” treatment conditions, a plasma exposure duration of 10 s (PP-HMDSO film thickness, d ∼ 40 nm) is found to be sufficient to reduce water absorption by 85%, while the corresponding reduction in CCl4absorption is small (<20%). The treatment demonstrates long-term stability, and it holds promise for commercial implementation on existing roll coaters.