Structure Design And Research Of PVDF/PVA/CaCl₂ Blend Desiccant Membrane

In order to solve the problem of gas-liquid entrainment of solution conditioning,the inorganic polymer overflow after absorption of organic polymer/inorganic moisture absorbent is further improved.In this paper,polyvinylidene fluoride(PVDF)was used as the skeleton,hydrophilic polymer polyvinyl alcohol(PVA)was used as the moisture absorption channel and binder,and CaCl₂ was used as the moisture absorption carrier.The composite volatile dehumidification was prepared by solvent volatilization induced phase separation(SEIPS).The microstructure,element distribution,gas permeability,water management capacity and mechanical properties were studied.Firstly,the influence of CaCl₂ content on its structure and dehumidification performance was discussed.In order to study the effect of CaCl₂on the crystallization and phase separation behavior of the membrane-forming system,the viscosity of the membrane-forming system was observed by rheological behavior test,and the crystallization process of the film-forming system was observed by thermodynamic microscopy.To improve the stability of the system,the increase of nucleation sites was beneficial to the increase of crystallization temperature.The microscopic morphology was observed by scanning electron microscopy.It was found that PVA and PVDF were blended to produce an interface micropore.In order to explore the mechanism of microporous structure,the element distribution was tested by EDAX and combined with theoretical analysis.The PVDF skeleton was open-wrapped with PVA,which fully utilizes the role of the PVDF organic scaffold without reducing the PVA hygroscopic capacity.In order to investigate the distribution of CaCl₂ in the interior,the distribution of Ca and Cl elements was tested by EDAX,and it was found that CaCl₂ was uniformly distributed inside the membrane matrix.In order to characterize the permeability of the pore structure of the membrane,it was characterized by gas flux,and the membrane moisture management capacity was comprehensively evaluated by dynamic contact angle test,moisture permeability test and water vapor adsorption capacity test.It was found that the PVA content was polymer quality.The 20 wt%and CaCl₂ content is 25 wt%of the polymer mass,the moisture absorption capacity of the dehumidification film is up to 1.65 g/g,the moisture absorption rate is 0.053 g/(g·min),and the moisture absorption stability is good.Then,by studying the effects of polymer concentration and water vapor induction time on the microstructure and moisture absorption behavior of the membrane,it was found that the structure of the composite porous dehumidification membrane was further regulated by water vapor induction,and the macroporous structure was more full,which was beneficial to the adsorption process..However,the loss of hygroscopic inorganic particles during the molding process resulted in a decrease in water vapor adsorption capacity.Although the affinity for water was lowered,the obtained porous structure was expected to be applied to other adsorption fields.As the polymer concentration increases,the viscosity of the casting solution increases.When the polymer concentration of the casting solution was 10 wt%and the water vapor induction time was 0 min,the moisture absorption performance of the porous hygroscopic membrane was the best.Among them,the water vapor adsorption rate reached 0.074 g/(g·min),and the adsorption amount reached 2.13 g/g.Based on the absence of any driving force,this study achieved a significant increase in moisture absorption rate and moisture absorption capacity,providing theoretical basis and technical support for the application of PVDF porous membrane in the field of air conditioning dehumidification.