Plasma surface functionalization of fibres and semi-finished fibre products

© Fraunhofer IFAM
Extensive plasma treatment at atmospheric pressure.
© Fraunhofer IFAM
Left: Untreated flax fiber textile. Right: Flax fiber textile (dyed), selectively plasma treated with increased wettability in treated areas.

In the project "Oberhalb" fibres and semi-finished fibre products are treated by means of  atmospheric pressure plasma sources for a cost-efficient and need-based improvement of their wettability and infiltration. This enables considerably shorter production cycles and better mechanical properties of the resulting fibre-reinforced polymers (FRPs).

Untreated fibres and semi-finished fibre products often show a low wettability and poor impregnation with many polymer matrix systems. Therefore, the fibre materials are usually sized in order to promote their adhesion to the matrix. However, the liquid sizing chemicals have to be customized to the used polymer matrix and require subsequent time- and cost-consuming process steps concerning the fibre drying and a proper utilisation of the chemicals.

Atmospheric pressure plasma processing offers an alternative dry and environmentally friendly physical technique for a cost-efficient and need-based fibre pretreatment in industry. Thereby, the fibre surface  can be gently cleaned and additionally activated due to the incorporation of polar, oxygen containing functional groups. This leads to a considerably improved wettability of the fibres with polymer matrix systems and promotes the adhesion formation between the two components.

In this project the plasma treatment of different types of fibres (natural, polymer, glas and carbon fibres) is carried out at atmospheric pressure. This allows compact systems that can be easily automised and integrated into processing chains if required.

Main focuses of the project:

  • Improvement of the wettability of fibers and semi-finished fiber products by means of dry plasma treatment at atmospheric pressure
  • Acceleration of fiber impregnation for reduced processing times
  • Improvement of mechanical properties of resulting composites
  • Extensive research on plasma treatment effects for various types of fiber materials
  • Development of custom-designed concepts for an inline plasma pretreatment of fibers


Project results:

  • Achievement of the process parameters for material-friendly pretreatment of various fiber materials for composite manufacture
  • Considerable improvement and acceleration of impregnation of fibers and therefore shorter processing times achieved due to plasma pretreatment
  • Increase of tensile strength of resulting composites partially achieved due to plasma pretreatment of the fibers
  • Analysis of framework conditions for integration of developed plasma processing into existing production lines

The project was funded by the state of Lower Saxony (funding number VWZN2990).