The effect of coagulant type on the physical and mechanical properties of regenerated cellulose membrane

Abstract

Modification of coagulant type, concentration and temperature are several ways to modify and determining the physical and mechanical properties of the regenerated cellulose membrane (RCM). This research was conducted by using two types of coagulant which were sulphuric acid (H2SO4), ammonium sulphate ((NH4)2SO4) and the combination of both. The precooled method was adopted to prepare the cellulose solvent which was consisted of NaOH and urea and precooled to -13 °C before cellulose dissolution process was conducted. Then, the cellulose solution was mixed vigorously, centrifuged and poured on the glass to form a thin layer of the solution before coagulated in the prepared coagulant bath. The coagulants used were prepared at different concentrations of 1 to 7 wt%. The regenerated cellulose membrane (RCM) formed by neutralisation and counter diffusion between solvent and non-solvent which the coagulant breaks the inclusion complex (IC) that was initially formed during the cellulose dissolution process. The RCM was allowed to dry by air drying for 12 hours at room temperature before characterization was conducted to analyse the membranes. Analysis results showed that RCM coagulated in distilled water has a higher mechanical strength followed by H2SO4 and (NH4)2SO4. However, membrane coagulated in the combined coagulant of 4wt% H2SO4/ 1wt% (NH4)2SO4 has higher tensile strength. The effect of types and concentration of coagulant on the physical, thermal and mechanical properties were characterized by using XRD, TGA and FTIR. Based on the results obtained, 4wt% H2SO4/ 1wt% (NH4)2SO4 were chosen as the main coagulant to study the effect of coagulant temperature on the membrane properties. For this study, the selected parameters of the coagulant temperature were 24 (room temperature(RT)), 40, 50 and 60 °C. Results for both XRD and mechanical analysis showed that samples coagulated at higher temperature have lower crystallinity and weaker tensile strength. For the mechanical properties, the tensile strength of samples reduced as the temperature increases. The results of this study showed that the changes in the type of coagulants and their conditions did affect the resulting physical and mechanical properties of RCM.