Emulsifying properties of cellulose oxalate and pectin from Norway spruce bark
Sammanfattning: Nanocellulose is a sustainable material and has shown interesting properties in various applications. One such application is Pickering emulsion, where the nanocellulose stabilizes the oil and water interface. Thus, this project aimed to evaluate a new type of nanocellulose, cellulose oxalate (COX), derived from different sources, dissolving pulp and bark, as a potential emulsifier. The properties of the nanocellulose, such as the chemical composition, morphology, aspect ratio, viscosity, and surface tension, are analyzed to determine how it affects the Pickering emulsion. Pectin has reported having emulsifying properties. Therefore, pectin derived from the bark was also studied as a potential emulsifier. The emulsion capacity and emulsion stability of the Pickering emulsion were estimated. Additionally, the emulsions were observed and visualized in an optical microscope, and it showed that all Pickering emulsions were successful. The COX and pectin particles were successfully adsorbed at the interface to form individual droplets which were stable enough not to coalescence. With the images from AFM, the aspect ratio and morphology of the particles were measured. COX pulp had an average width of 5.5 nm and an average length of 372 nm. COX bark had an average width of 3.9 nm and an average length of 257 nm. Notably, COX pulp does have a slightly higher aspect ratio than COX bark. DLS was another way the particle size was measured. However, it was not a suitable technique because both COX did indicate a relatively polydisperse system and are therefore not suitable to be measured by DLS. Furthermore, the viscosity of the COX pulp and COX bark suspensions were measured with an Ubbelohde capillary viscometer which was not an ideal method because the COX suspensions were too thick and gel-like for the instrument and got clogged constantly. As expected, the surface tension decreased steadily, more so for COX pulp than COX bark with increasing concentration. Then again, this means that COX has a hydrophobic property that does reduce the surface tension of water. Lastly, the carbohydrate analysis did indicate that both COX do have a high amount of glucose. Moreover, both COX did also show a significant amount of other components. Overall, this study does conclude that COX pulp, COX bark, and pectin did stabilize the Pickering emulsion to some degree, despite being inconsistent and can therefore be considered effective emulsifiers.
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