Conversion of paper to film by ionic liquids: manufacturing process and properties
In this study, we investigate the “chemical welding” of paper with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) using a two-step process. First, the IL is transported into the structure of the paper as a water solution. Then, partial dissolution is achieved by activation with heat (80–95 °C), where the water evaporates and the surfaces of the fibres partially dissolve. The activated paper is washed with water to remove IL, and dried to fuse fibre surfaces into each other. The “chemically welded” paper structure has both elevated dry and wet strength. The treatment conditions can be adjusted to produce both paper-like materials and films. The most severe treatment conditions produce films that are fully transparent and their oxygen and grease barrier properties are excellent. As an all-cellulose material, the “chemically welded” paper is fully biodegradable and is a potential alternative to fossil fuel-based plastics.
KeywordsCellulose Partial dissolution Paper Ionic liquids All-cellulose composite
This study was carried out in the CellFi (Conversion of cellulose to plastic) project funded by Business Finland and Finnish industries companies (Metsä Fibre Ltd, Metsä Board Ltd, Stora Enso Ltd, FL Pipe Ltd, Pölkky Ltd, and Versoul Ltd). Mika Vähä-Nissi is acknowledged for his comments on the barrier measurements, Heikki Pajari is thanked for performing viscosity analyses, and Tommi Virtanen is thanked for performing the NMR analyses. Professor Ilkka Kilpeläinen (University of Helsinki) is thanked for active participation in the CellFi project.
The manuscript was written through contributions of all the authors. All authors have given approval to the final version of the manuscript.
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