Study Of Structural Modulation And Performance For Oxygen-Rich Membranes With Fluorinated PDMS By Electrospray Additive Manufacturing

Oxy-fuel combustion has received considerable attention as it is widely regarded as a promising method of improving combustion efficiency and low-cost CO₂ capture.The development of technologies for low-cost oxygen or oxygen separation from air is therefore essential.The three main technologies for separating oxygen from air include membrane technology,adsorption technology and oxygen decoupling chemical cycle technology.Membrane technology is considered to be an energy efficient oxygen enrichment technology.The fluorinated PDMS membranes prepared in this paper can be effectively used in oxygen enrichment to improve oxygen permeability and selectivity.In this paper,Polydimethylsiloxane（PDMS）membranes with tetraethyl orthosilicate（TEOS）as the crosslinker and PDMS membranes with perfluorodecyltriethoxysilane（PFDTES）as the crosslinker were prepared using the conventional casting method.The effects of different crosslinker qualities（same molar ratio of both crosslinkers）on the structure,mechanical properties,thermal stability,oxygen permeation properties,nitrogen permeation properties and selectivity of the PDMS membranes were investigated while maintaining a solid content of 10%.The results show that the oxygen permeability and nitrogen permeability of PDMS membranes show a trend of increasing and then decreasing with increasing mass of crosslinker.The oxygen permeability and selectivity of the PDMS membrane were 542.9 Barrer and 1.86 respectively at a PDMS to TEOS molar ratio of1:9.6.The oxygen permeability and selectivity of the PFDTES cross-linked PDMS membrane were higher when comparing the two cross-linkers in the same molar ratio.At a PDMS to PFDTES molar ratio of 1:4.8,the PDMS membrane could achieve an oxygen permeability of 962.7 Barrer and a selectivity of 2.09.In order to further improve oxygen permeability and selectivity and to overcome the negative effects of membrane thickness,PDMS membranes were prepared by electrospraying.The molar ratio of PDMS to PFDTES was fixed at 1:4.8,and the PDMS membrane was sprayed by varying the voltage parameters of the electrostatic spinning equipment within a certain range.This is because the electrospray method of membrane production not only allows precise control of the membrane thickness,but also allows the size,morphology and structure of the micro and nano particles to be regulated by changing the spraying conditions,resulting in better and more homogeneous performance of the prepared membrane.The effects of different voltages on the structure,mechanical properties,thermal stability,oxygen permeation properties,nitrogen permeation properties and selectivity of PDMS membranes are investigated.After a gas permeability test study,the membranes sprayed at a voltage of 14 k V showed the highest oxygen permeability of1405.0 Barrer and a selectivity of 2.66.The above experiments have shown that the fluorine cross-linked PDMS membranes have better oxygen permeability and selectivity compared to the conventional tetraethyl orthosilicate cross-linked PDMS membranes.The oxygen permeability and selectivity of the membranes were further improved after the PDMS membranes were prepared using the electrospray method.The average thickness of the membranes prepared using the conventional casting method in this paper ranged from 320-340μm,whereas the electrospray method produced controlled membranes with an average thickness of 50-70μm,which was much thinner than the PDMS membranes prepared by the conventional casting method.