The master’s thesis involved determining the appropriate preparation of hydrogel samples from cationic nanofibrillated cellulose (QCNF) and graphene oxide and examining their rheological properties. Graphene oxide (GO) is an oxidized form of graphite that, due to its unique structure, possesses numerous beneficial properties. Various studies have demonstrated that incorporating graphene oxide into the hydrogel matrix enhances the hydrogel's properties. This research focused on studying the impact of adding graphene oxide to QCNF hydrogel on its rheological properties. QCNF is a type of nanocellulose in the form of nanofibrils with a quaternary ammonium salt functional group (EPTMAC). Prior to hydrogel preparation, I characterized the QCNF suspension, with results matching the manufacturer's data. For the appropriate preparation of QCNF hydrogel, I initially determined the use of an ultrasonic homogenizer. It was later found that using a propeller mixer to blend QCNF and GO disrupted the properties achieved with the ultrasonic homogenizer. Consequently, I excluded the propeller mixer from the preparation process, thereby reducing the preparation time. For preparing QCNF hydrogel with GO, I used both GO suspension and GO powder. QCNF hydrogels with added GO suspension exhibited promising rheological parameter values. The Maxwell shear modulus (G) values for the hydrogel from QCNF and GO suspensions reached up to 5,700 Pa, while the viscosity (η0) values reached up to 182,000 Pas. A challenge with using GO suspension was the repeatability of homogenization results and, thus, the reproducibility of the structure. For this reason, I later used GO powder, which I mixed into the QCNF hydrogel samples in appropriate mass ratios. I found that the values of G and η0 increased with the total mass fraction of the hydrogel. Hydrogels with a higher mass fraction of GO exhibited higher rheological parameter values compared to those with a lower mass fraction of GO, confirming that GO positively influences rheological properties. I also compared hydrogels prepared from QCNF and GO powder (QCNF+GO) with hydrogels from anionic nanofibrillated cellulose (TOCNF) and GO powder (TOCNF+GO). The rheological properties of the TOCNF+GO hydrogel also improved with the hydrogel's mass fraction, although the properties changed differently compared to the QCNF+GO hydrogel due to structural differences. Finally, I examined the time-dependent rheological properties of the QCNF+GO hydrogel. In the initial days, the rheological properties increased, then stabilized after a certain period. Among the QCNF+GO hydrogel samples, the most promising sample was the hydrogel with the highest mass fraction of QCNF and GO. For industrial applications, further research would be required to determine how the rheological properties change over a longer period. If it can be shown that the properties stabilize and the rheological parameters do not begin to decline, QCNF+GO hydrogels would have promising potential for use in various industrial sectors.
|
