Chemical engineers in the US have developed a practical atmospheric plasma treatment process for depositing stable hydrophobic coatings on a range of materials.

The process developed by Seong Kim, assistant professor at Pennsylvania State University and colleagues uses a methane-helium/argon mixture. A smooth hydrocarbon layer can be deposited on a range of substrates, both metallic and insulating, under the same operating conditions. The result is a material with both good and durable hydrophobicity regardless of the substrate.

Materials with hydrophobic coatings are used in the production of waterproof clothing and in corrosion prevention. Plasma-based techniques, which slowly pass a substrate under the ionised gas, are often used to deposit the coatings. This is because they do not produce any chemical waste and it can be fully automated. 

In the past such techniques were slow and not suitable for continuous in-line manufacturing because the samples needed to be transferred into and out of a vacuum system. Recently plasma processes at atmospheric pressure have been used to overcome this problem, but plasma stability and low power operation have remained challenging.

Kim said the system could easily be scaled up for continuous in-line processing. This is because of the stability of the hydrophobic coating and the wide variety of materials that can be coated, together with the fact that the technique operates under atmospheric conditions.

Caroline A Moore