The mass transfer channel of the membrane absorption process is provided by the micropores in the membrane material, if the membrane material is unstable or the operation is not standardized resulting in water ingress into the micropores, the mass transfer performance will be completely lost. Therefore, the stability of the membrane absorption process is completely dependent on the stability of the membrane material and operational stability, a reasonable choice of membrane materials is essential. Commonly used membrane materials are hydrophobic microporous polymer membranes, including polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP) and polyethylene (PE). Among these hydrophobic materials, PE, PP and PVDF are the more versatile polymers with low price and good chemical and thermal stability.

    However, in the research process of scholars and industrial applications, it has been found that PVDF, PP and PE materials are generally degraded and the membrane structure may be changed after long-term contact with the absorbent [1], and the mass-transfer performance decreases dramatically everywhere. Studies on the compatibility between membrane materials and absorbents have also been reported and analyzed. For example, aqueous solutions of amines (e.g., MEA ethanolamine) are commonly used as absorbents in industry, but as commonly used membrane materials, PE, PP, or PVDF, it was found that irreversible degradation of the materials occurred when they were in long-term contact with alcoholic amine solutions [2]. The chemical reaction between the amine solution and the membrane material leads to changes in the membrane material properties, such as: membrane pore structure, interfacial properties (so that the membrane tends to be more easily wetted), gas permeability, or gas-liquid mass-transfer efficiency, leading to a loss of mass-transfer performance. 

   Since PP and PVDF materials are easy to prepare into hollow fiber membranes with suitable porosity and pore size, these materials are still more commonly used in scientific studies of membrane absorption. However, there are still significant challenges when considering the application of these membrane materials on an industrial scale.

   A more feasible approach for industrial applications is the use of perfluorinated polymers, such as the "king of plastics," polytetrafluoroethylene (PTFE), which is an extremely chemically stable, mechanically strong, and hydrophobic membrane material. However, PTFE membrane materials can not be prepared using the traditional phase transition method of porous membrane, and PTFE hollow fiber membrane pore size and porosity is more difficult to regulate, so at present only a few people in China can prepare a stable performance and uniform pore size PTFE hollow fiber membrane (such as the Dalian Institute of Chemical Technology).

【2】D. Demontigny, P. Tontiwachwuthikul, A. Chakma, Using polypropylene and polytetrafluoroethylene membranes in a membrane contactor for CO2 absorption, Journal of Membrane Science[J], 277 (2006) 99-107.