Chemical aspects of the preparation of Vulcanised Fibre using zinc chloride hydrates
From a brief history to a new consideration of the key reactions in ionic liquids
Allner, Lukas, Vaíllo, Gonzalo, Schmidbaur, Hubert and Schmidbaur, Karolin. "Chemical aspects of the preparation of Vulcanised Fibre using zinc chloride hydrates: from a brief history to a new consideration of the key reactions in ionic liquids" Zeitschrift für Naturforschung B 80, no. 5 (2025): 135-146. https://doi.org/10.1515/znb-2025-0013
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In work of the mid-19th century, it has been shown that the physical properties of cellulose and related materials are changed drastically upon their immersion in “aqueous zinc chloride solutions”, followed by washing to remove the salt and drying the resulting fabric, whose chemical composition did not change, but had a different structure. It was soon recognized that the process worked only at very high concentrations of zinc chloride, but it was
only in the last decade that the “solutions” were finally identified to be in fact ionic liquids with an optimum performance for the trihydrate ZnCl2(H2O)3 which is built up of [Zn(H2O)6]2+ cations and [ZnCl4]2− anions, both in the solid state and in the melt, and which has a melting point of 6.5 °C. The production of Vulcanised Fibre has long been an important industrial process based on the treatment of cellulose with zinc chloride following established protocols. In the present paper the consequences of the ionic liquid concept for the underlying processes are discussed on the
molecular level, proposing a sequence of reversible reactions, which allow the reorganization of the cellulose structure under surprisingly mild conditions. Due to its advantageous properties as a biomaterial, the all-cellulose, selfreinforced composite is currently being rediscovered for newly considered applications within several industries such as the construction industry as one example. Its strength, lightweight and plasticity present unique opportunities for architectural as well as structural applications.
Keywords: Vulcanised Fibre; ionic liquids; zinc chloride hydrates; cellulose; all-cellulose composite; building material