Study On Preparation And Structure Of Poly (Vinyl Alcohol)/ Cellulose Nanocrystal Composite Membrane Material

In this paper Poly(vinyl alcohol) (PVA) membranes used for pervaporation were modified through several different methods. Among these modified membranes Poly(vinyl alcohol) (PVA) /cellulose nanocrystal (NCC) composite membranes perform best in pervaporation process. During the preparation of the composite membrane, the nano cellulose was blended with PVA casting solution using ultrasonic treatment. It was investigated that the effects of preparation factors on membrane structure, pervaporation and mechanical performance of composite membrane. With the addition of NCC, the mechanical properties of the nanocomposite membranes were improved. Moreover, the nanocomposite membranes had good pervaporation properties. Among all the prepared membranes, PVA/NCC nanocomposite membrane containing 2%(wt) NCC exhibited the best separation factor.The effect of nano cellulose on performances of composite membrane was studied by testing various properties. The hydrophilic property and anti-fouling property of composite membranes were improved, which was attributed to the existence of nano cellulose. The composite membrane was characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetric(DSC) and thermogravimetry (TG). Atomic force microscope (AFM) was used to characterize the cellulose nanocrystal. The characterization results demonstrated that cellulose nanocrystal (NCC) displayed slender rods and dispersed homogeneously within the PVA matrix, which could be assigned to the hydrogen bonds formed between PVA and NCC. The DSC and TG analysis demonstrated that the nanocomposite membranes exhibited an increase in melting temperature and higher thermal resistance. With the addition of NCC, the mechanical properties of the nanocomposite membranes were improved. Moreover, the nanocomposite membranes had good pervaporation properties. The structures of these pervaporation membranes were also studied. The effection of crystallinity and thickness on pervaporation properties showed that:Compared with micro-nano cellulose, there had been stronger interaction between nano cellulose and PVA molecule, and thus made more stability of PVA/cellulose nano-composite membranes in both chemical and physical properties. The effect of operate conditions during PV process was also investigated.