2023

Ahokas, Pauliina; Khakalo, Alexey; Jaiswal, Aayush; Koso, Tetyana; King, Alistair W. T.; Spönla, Elisa; Harlin, Ali; Orelma, Hannes

Regenerated cellulose products are attracting increasing attention as sustainable alternatives to petroleum-based materials, especially in the packaging and textile industries. Ionic liquids (ILs) are often described as “green” options for cellulose dissolution due to low toxicity and volatility. Most studies on the dissolution and regeneration of cellulose utilize high-purity dissolving pulps, which are known to be more “reactive” than kraft pulps. Therefore, we investigated the influence of hemicellulose content on solubility and regeneration ability of softwood kraft pulps as well as dissolving grade softwood sulfite pulp, by using aqueous solutions of a novel recyclable superbase-based IL, [mTBN-H][OAc]. The fiber solubility was studied by following dissolution rate and solution quality by rheological means and optical microscopy. Carbohydrate compositions of the kraft pulps were varied by reducing the hemicellulose content using cold caustic extraction (CCE). The molecular masses of the pulps were also controlled by an alkaline hydrogen peroxide treatment. The prepared pulps and regenerated materials were characterized by their carbohydrate compositions, liquid-state nuclear magnetic resonance (NMR), moisture sorption, and mechanical properties. The effect of water on the dissolution rate, dissolution time, and completeness of dissolution is described. The effect of the hemicellulose content on the mechanical properties of the regenerated films was also tested.