Incorporation of Plasticizers through Refining into Wood Pulp : A Potential Route For Bio-based Thermoplastic Materials

Sammanfattning: Fibers are interesting materials alternative to replace conventional fossil-based plastics, as they are bio-based and do not lead to CO2 emissions. Due to their limited ductility, it is difficult to use them to make complex three-dimensional shapes. This problem has already been addressed in previous research studies but the processing conditions used here were never tried before. In this thesis, the incorporation of low molecular plasticizers onto the fibers is investigated to obtain a more ductile fiber-based material. More precisely, Paper and Fiber Research Institute (PFI) refining is used to mechanically treat the fibers and help the sorption of glycerol, urea, polyethyleneglycol (PEG), or polyvinylalcohol (PVA), followed by the formation of sheets from the modified pulp. However, it has been found that only small amounts of plasticizers were retained by this process. The refining itself on the fibers without additives enhanced fibrillation and developed mechanical bonding between the fibers, which resulted in increased strength and ductility. Also, the hot pressed (HP) drying technique was found to yield denser and stronger papers, compared to the non-pressed (HP) drying technique. As a comparison, the incorporation of plasticizers through ultrasonication and its effect on the paper properties were also considered from a previous study within the same research group. It has been found that this mechanical treatment retains more plasticizers than refining but yields different paper properties (especially an increased ductility). All these results suggest that PFI refining should be studied more in-depth by performing at least one process optimization cycle where less dilution takes place.