Modifying the surface tension
Increasing or reducing the surface tension (resp. surface energy) of solid surfaces is one of the primary applications of plasma technology. High surface tension provides for:
- good wettability by liquids and thus
- good adhesion of paints, inks, adhesives, solders
- good filtering properties of porous materials
Low surface tension provides for:
- water-repellence and thus
- water-proof fabrics
- non-soiling and self-cleaning surfaces
- no attack by reactive liquids
- Epilamisation: prevents dissolving of lubricating oils
High surface tension is achieved by:
- Removal of separating substances by plasma cleaning
- Removal of oxide layers on metals, in particular by treatment in a hydrogen plasma
- Plasma activation by generation of polar groups, in particular oxygen bonds in the oxygen plasma
- Plasma coating by plasma polymerisation of hydrophilic coats, in particular polyvinyl acetate
Low surface tension is achieved by:
- plasma coating with hydrophobic polymers, in particular by using fluorine monomers as a process gas and polymerisation to PTFE-like coats or HMDSO and polymerisation to quartz-like coats.
