Study On Cellulose Dissolution And Regeneration In Chloride System And Film Forming Properties

Nowadays,human beings face the challenging issue about environmental pollution and fossil energy shortage.Nevertheless,cellulose as a sustainable and abundant biopolymer,has been widely used in a broad range of applications.However,cellulose is hardly dissolved in water and common organic solvents due to the hydrogen bonds formed inside the cellulose molecule,which makes it so difficult to be directly utilized.Therefore,looking for a green and facile method for dissolving cellulose,and preparing the dissolved cellulose into a film would facilitate the high value-added utilization of cellulose.In this study,the inorganic chloride salts as green and environmentally friendly solvents were used as cellulose dissolving reagents.Then the effect of the solvents type,temperature and reaction time on the cellulose dissolution were explored to obtain a comprehensive mechanism analysis.On the basis of cellulose dissolution in inorganic chloride salts,we further explored the degradation performance of regenerated film,providing a theoretical basis for the research on the cellulose dissolution and regenerated films.The main research contents as follows:（Ⅰ）Study on the dissolution behavior and mechanism of cellulose in chloride solution.In the study,four inorganic salt solutions of Li Cl,Zn Cl₂,Ca Cl₂and Fe Cl₃ with different numbers of water molecules were selected to explore their dissolution of cotton fiber at different temperatures.The optical microscope and thermal polarization microscope（POM）results showed that cotton fibers were dissolved in Zn Cl₂·3H₂O and Fe Cl₃·6H₂O efficiently（5-20 min）.According to the field emission scanning electron microscopy（FE-SEM）results,the surface morphology of the regenerated fibers was all changed.Also,it was found that the hydroxyl peaks of the regenerated fiber were blue-shifted observed by infrared spectroscopy（FT-IR）.The results of thermogravimetric analysis（TG）and X-ray powder diffractometer（XRD）proved that the thermal decomposition performance of the regenerated fiber was weakened and the crystal configuration of the fiber regenerated from Zn Cl₂·3H₂O was changed,indicating that the internal hydrogen bond network of cellulose was broken during the cellulose dissolution process.Finally,the mechanism analysis suggested that the cellulose dissolution was achieved by hydroxyl group on cellulose replacing part of the water molecules in the coordination sphere of the metal ions,namely,the water amounts carried by the metal ions played a vital role in the cellulose dissolution,which provided fundamental knowledge for the selection of more efficient solvents.（Ⅱ）Study on regeneration of cellulose into film based on dissolution and its life cycle.In this study,transparent cellulose film was prepared using solution casting method after dissolving cotton fiber in Zn Cl₂·3H₂O solution.The optical microscope and ultraviolet-visible spectrophotometry（UV-vis）showed that the cellulose regenerated film has good optical properties.In next period,PBS degradation and UV aging as well as soil degradation were carried out combined PE films and biodegradable film（PBAT film）for studying the degradation behavior of the three types of films.Compared with PBAT film and PE film,regenerated cellulose film showed a shorter degradation cycle in three types of degradation tests.Especially in soil degradation,the mass loss rate of regenerated cellulose film reached 99.1%after 14 weeks of soil burial.This study is helpful to understand the life cycle of regenerated cellulose film in the natural environment and the corresponding degradation behavior,providing research ideas for the future development of environmentally friendly and degradable packaging materials.