Regenerated Cellulose-Based Composite Films: Preparation And Performance Analysis

As the most abundant natural polymer in nature, cellulose is renewable, biodegradable, and biocompatible. However, performances of regenerated cellulose（RC） films obtained from cellulose solvents need to be improved. Therefore, it is urgent and promising to develop cellulose-based composite films to broaden the application of cellulose.In this thesis, cotton liner and Na OH/urea/H₂O were used to prepare RC-CaCO₃/PVA composite films by three different methods, including in-situ precipitation, mixing solution, and solution immersion, where Na OH/urea/H₂O was adopted as the cellulose solvent. The structures and properties of the composite films were characterized by a series of methods, including Scanning Electron Microscopy（SEM）, Ultraviolet-visible Spectrophotometer（UVVis）, Thermal Gravity Analysis（TGA）, Fourier Transform Infrared Spectroscopy（FTIR）, Xray diffraction（XRD）, mechanical property test, and permeability test, to evaluate the qualities of the composite films produced by different methods. The investigations revealed that the composite films demonstrated much better thermal stability, mechanical property, oxygen barrier property, and other improved advantages when compared with the original RC films.The main results for three types of novel RC-CaCO₃/PVA composite films are summarized as follows:（1） The regenerated cellulose-CaCO₃ films were fabricated by introducing in-situ precipitation CaCO₃ particles into the wet RC films, in which the RC films were used as matrixes. The structures and morphology of the RC films and RC-CaCO₃ composite films were characterized by SEM and XRD. The results indicated that the CaCO₃ particles were successfully formed in the matrix. FT-IR results demonstrated that there were strong hydrogen bonding interaction between cellulose and CaCO₃ particles. The TGA and mechanical property analysis showed that when the concentration of CaCl₂ was lower than 0.8M, the tensile strength and elongation at break of the composite films increased with the increasing CaCl₂ concentration. When the concentration of CaCl₂ increased to 1M, the tensile strength and elongation at break turned down. The mechanical property decreased due to the agglomeration of CaCO₃ particles at higher content. Then we could conclude that 0.8M was the optimal concentration in our experimental value. Therefore, the in-situ precipitation method was simple and effective, which might be used for the preparation of cellulose-based composite materials.（2） The regenerated cellulose-PVA composite films could be prepared by blending the cellulose solution with PVA solution. FTIR and XRD results showed that cellulose and PVA just blended physically, and the hydrogen bonding interaction formed between them leading to the decrease of crystallinity. TGA result demonstrated that a certain amount of PVA content could improve the thermal stabilities of the composite films. The mechanical property test and oxygen permeability test indicated that when the mass ratio of cellulose and PVA was 92:8, the composite film possessed the best tensile strength, Young’s modulus, and oxygen barrier properties. So it turned out that a certain amount of PVA could improve the thermal stabilities, mechanical strength and oxygen barrier properties.（3） The regenerated cellulose-PVA composite films were prepared by immersing the RC films into the PVA solutions. The analysis of transparency showed that the composite films owned good transparency. FT-IR and XRD results demonstrated that there were strong hydrogen bonding interaction between cellulose and PVA. Meanwhile, the analysis of mechanical property and oxygen permeability indicated that when the RC film was immersed into 5% PVA solution, the tensile strength, elongation at break and oxygen barrier property of the composite film improved significantly. Particularly, the tensile strength and elongation at break would be increased by 27.94% and 23.98%, respectively, and the oxygen permeability decreased by 72%. These results suggested that the prepared composite films could have great potential application in the field of packaging materials such as food packaging films.