Properties affecting the rheology of alkaline cellulose solutions

Cellulose is the most abundant biopolymer on earth and it is a versatile building block for multiple purposes, for example in paper, board and textile industries, and as its derivative form, such as cellulose acetate, ethers or esters, it can be exploited for example in pharmaceuticals and packaging. However, utilization of cellulose in high performance purposes requires its dissolution, in order to enable the regeneration of the structure. Cellulose dissolution is challenging due to the semi-crystalline structure, tight hydrogen bonds within the polymer sheets and the structure with both hydrophilic and hydrophobic heads. For this reason, cellulose structure first needs to be altered through derivatization or otherwise increasing its accessibility, for example by means of enzyme treatment prior to dissolution. The aim of the study was to compare different activation mechanisms and raw materials, and examine how these factors affect the solution rheology and stability. The latter is a significant factor affecting processability of the solution in regeneration of the solution into a form of fibres or films. Literature part covers chapters of cellulose structure, different activation mechanisms and dissolution, as well as factors affecting it. Additionally, theory shortly discusses of the features affecting regeneration and rheology of solution. Experimental part consists of dissolving cellulose pulps with different pretreatments, after which, solutions are examined in means of solubility and stability. As a reference material, viscose performed as expected, exhibiting the highest level of dissolution, and gelled after around five days. Most importantly, enzyme-treated cellulose exhibited positive effect on solution stability, remaining processable longer that viscose. It was also concluded that consisted process conditions cannot be applied for different raw materials without optimizing the process for each raw material individually