Modified cellulose synthesized by different deep eutectic solvents as an additive in paper making process

Abstract: The environmental concerns that come with the currently used traditional papermaking process where petroleum-based additives are used, has tempted researchers to study “green” additives by introducing environmentally friendly modifications of cellulose as an additive in the papermaking process. This thesis will spin further on that by producing additives with different charge densities and focus on to incorporate an etherification reaction into potentially greens systems based on non-toxic and readily biodegradable deep eutectic solvent (DES). Before modifying the cellulose with DES, an oxidation of cellulose to dialdehyde cellulose (DAC) with sodium periodate as oxidizing agent, took place. The high reactivity of the aldehyde groups in DAC serves as a starting material for further derivatization. The aldehyde content (AC) in the DAC was measured using titration. Additionally, the charge densities (mmol/g) of all modified pulps were determined by using a particle charge detector. The dewatering and drainage abilities of the different modified pulps was determined by measuring the drainage (°SR), the moisture ratio (g/g) before and after vacuum dewatering, and the water retention value (g/g).  The tensile strength index was tested on the paper sheets and all parameters were compared with a reference pulp to find out which ionic DES was the most effective in modifying cellulose and using it as a wet-strength additive. From the result gained, one can see that there is a correlation between charge density and mechanical strength as well as the fibres capability to retain water. Generally, swelling considerably improves the strength properties of paper meanwhile the additives with strength-enhancing effects are also the additives that decrease the dewatering capacity. The conclusions from this work are that DESs reagents can work as sustainable modification methods for increasing the mechanical strength of papers together with oxidation of cellulose. In particular the cationic AH-G additive, which in accordance with other studies, show that cationic additives are better in increasing the mechanical strength than anionic because of their ability to adsorb to anionic fibers.