Materials and geometries suitable for plasma treatment

Materials suitable for plasma treatment

In low-pressure plasmas that work at reduced pressure, all solids that are vacuum-compatible can be treated:

  • Metals
  • Most polymers
  • Biomaterials and many other organic and inorganic substances.

The advantages of the low-pressure technology are the unparalleled layer homogeneity as well as the extremely low consumption of chemicals. With plasma processes, in particular low-pressure methods, even chemically inert materials such as Teflon® can be modified and made accessible to further processing (e.g. bonding). However, there are material related limits when materials are corroded too strongly in the plasma, whether chemically or by (UV) radiation as in the case of the plastic polyoxymethylene (POM).

Wide range of geometries

  • Shaped bodies (Container)

Most products are to be coated three-dimensionally, covering the entire surface. The plasma’s ability to access the entire exposed surface plays a decisive role in the homogeneity of the treatment.

  • Flat materials (Foils, textiles, membranes)

2-D objects such as foils can be processed relatively easily. Woven textiles, fleeces and membranes can also be treated in plasmas. Here, depending on the application, we can selectively influence the in-depth effects of the plasma: Either that a functionality is only required on the surface, or that the bulk material is to possess the same characteristics. The Fraunhofer IGB has a plant for the semi-continuous treatment of textiles.

  • Pipes and tubes

We also treat pipes and tubes in plasmas, the outside as well as the inside. Physically, one comes up against limits for inside treatment when the inside diameter (lumen) is substantially less then a millimeter. Here, the dependence on the process and material requires an appropriate amount of development work. At the Fraunhofer IGB we have already treated materials with inside diameters of less than 200 μm.

  • Fibers and threads

We also treat fibers and threads as 1D solids. For this, we have continuous plants that work with low-pressure plasmas but where it is nevertheless possible, due to a sluice system, to guide the fibers “from air to air”. As a result, the system can, for instance, be positioned directly in-line behind an existing fiber production plant (in-line operation).

  • Granulates and powders

Finally, there are also granulates and powders (micro-to nano-particle size). The smaller the grain size of the material, the more difficult the treatment. This is due to the charge of the material in the plasma, as a result of which the particles are considerably more difficult to control and process. However, plasma treatment is also possible in this case by means of selective adaptations. At the moment we are working on the modification of CNTs (carbon nanotubes).