Utilization of soft dual coagulation for the synthesis of hydrophobic PVDF membrane for membrane gas absorption of CO2

摘要

Highly hydrophobic membranes have catch the attention of many researchers worldwide due to its prospective application in industry and daily life. Hydrophobic microporous were extensively used in separation process such as membrane distillation, membrane contactor, and others. In these processes, the penetration of aqueous solution into membrane pores needs to be prevented, therefore the hydrophobic property of the membranes were very crucial.There are several methods in preparing highly hydrophobic membranes. Khayet et al. (Khayet ef a/., 2002) used the method of surface modification to improve PVDF membranes to be used in pervaporation. Effect of ethanol in water bath were studied by Deskmush and Li (Deshmukh and Li, 1998). Meanwhile, the utilization of solvent in the coagulation bath or the addition of solvent into a water bath may encourage a delayed liquid-liquid demixing of a polymer and eventually results in the formation of membranes with sponge-like structure (Yeow et al., 2004). Li et al. (Li et al.) used mixed solvents (TEP-DMAc) in casting solution and coagulation bath to control the morphology and hydrophobicity of the prepared PVDF membranes. Polyvinylidene fluoride (PVDF) is a commercially available fluoropolymer with low surface energy (25 dynes/cm) and good physical, chemical, and mechanical properties Since PVDF is the only hydrophobic polymer soluble in the organic solvents, the phase inversion process can be used for asymmetric membrane fabrication. PVDF has a good solubility in many common organic solvents such as Dimethyl Formamide (DMF) (Lin et al., 2003), Dimethyl Acetamide (DMAc) (Yeow et al., 2005; Yan et al., 2006; Elashmawi, 2008), N-methylpyrrolidone (NMP) (Shi et al., 2008), Dimethyl sulfoxide and Triethylphosphate (TEP) which can easily be prepared by using phase inversion method (Lin et al., 2006) particularly Non solvent Induced Phase separation (NIPS) method (Kuo et al., 2008).