Polyelectrolyte coating: A new approach to surface treatment of natural fibers

Madina Shamsuyeva, Fraunhofer Institute for Wood Research WKI, Application Center HOFZET, Hanover, Germany

Due to their beneficial material properties, availability as well as ecological and economical aspects, natural fiber-reinforced polymer composites (NFC) find many applications in various industrial sectors like sports, leisure or the automotive sector. Parallel to the growing volume of the commercially supplied NFC, the quality demands regarding their performance are steadily rising. Nevertheless, such drawbacks of the natural fibers like high moisture absorption during storage, emission development during processing at a temperature higher than 200°C or the poor fiber-matrix adhesion in polymer composites are still not met with established solutions, which could be applicable for the use in large-scale production of NFC.

In this context, coating of the natural fibers with polyelectrolytes via Layer-by-Layer method (LbL) offers a promising solution. This environment-friendly, cost-effective and simple method implies alternative adsorption of polyelectrolytes on the charged substrate. The chemical composition, thickness, and the morphology of the produced PE multilayer coating can be easily controlled through large number of available polyelectrolyte types, the number of the adsorbed layers, the deposition method, and process conditions like pH, temperature, etc. At the moment, the method is commercially used in medicine for manufacturing biocompatible coatings for implants, contact lenses and drug delivery systems.

This contribution focuses on the application-oriented adaptation of this method for the surface treatment of NF. The changes of morphological and chemical properties occurring during and after the coating of viscose fibers via LbL method with polyethylene imine (PEI) and polystyrene sulfonate (PSS) under various treatment conditions, i.e. different pH values, PE and salt concentration as well as the effect on the mechanical properties of the corresponding composites will to be discussed.

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