Preparation And Properties Of 3D-PEEK Network Reinforced SPEEK Membrane

The coal,oil and other non renewable energy have been increasingly scarce in the last dozen years or so,global energy shortage began to appear,and the ecological environment around the world is accelerating the deterioration due to the depletion of fossil fuels,the two problems are urgent to be solved.It has forced that people to seek and develop clean energy,in order to realize sustainable development of the global economic and environment.Fuel cell technology stands out,especially in transportation and handheld devices.Proton exchange membrane fuel cells(PEMFC)are attracting considerable attention as new-type green energy,and proton exchange membrane(PEM)is a core component of proton exchange membrane fuel cell which directly influences the performance of PEMFC.Nafion-based polymers are widely used as PEM because of their excellent mechanical,chemical,thermal stability and high proton conductivity.However,some shortcomings associated with high cost,heavy pollution and low proton conductinity at high temperature have drawn great attention to development of new and low-cost electrolyte polymers to substitute for Nafion.Sulfonated poly(arylene ether ketone)material(SPAEK)was a new kind of PEM materials with excellent performance,good thermal,chemical and mechanical stability,high proton conductivity,and lower cost.Firstly,Three kinds of sulfonated poly(arylene ether ketone)materials were prepared,and the thermal stability of three kinds of membrans was studied,found that thermal stability of Na-SPEEK was superior to two other materials,therefore,the SPEEK was selected as the polymer matrix materials.However,SPEEK also has some drawbacks in its practical application because membrane properties depend too strongly on the degree of sulfonation(DS).The proton conductivity of SPEEK increased with a higher DS.However,the swelling ratio increases with DS of SPEEK increases,and the dimensional stability and mechanical strength decrease sharply,these shortcomings hindered its application for fuel cell.In order to overcome the shortcomings,it is essential to modify the SPEEK membrane properly.Recasting is the most commonly used approach to prepare proton exchange composite membrane,which the inorganic or polymer particles is directly dispersed into membrane with solution,emulsion,and other forms of molten polymer,a combinatorial approach of recasting and ultrasonic were used sometimes to improve the dispersion of inorganic particles.The recasting method offer unique advantages to the preparation of thin membranes and easy optimization of the processing parameters.This work is aiming to reduce the water swelling ratio to improve the dimensional stability of SPEEK composite menbranes and ensure the high proton conductivity and mechanical strength.Polymer-inorganic,polymer-polymer and multi-component proton exchange membranes were prepared respectively by recasting and thermal treatment method.In this paper,the modification of SPEEK composite membranes by thermal treatment was studied.SPEEK with different DS was prepared by post sulfonation,and the IEC value,water uptake,water swelling ratio and proton conductivity of SPEEK with different DS were compared,the Na-SPEEK 65(S65Na)with DS of 0.65 was selected as polymer matrix membrane.Poly(ether ether ketone)(PEEK)is a poriferous,thermoplastic semi-crystalline polymer used in a number of high-end applications which demand durability and robustness.Superior performance properties of PEEK include its high thermal stability(Tm=343 oC),high mechanical strength,stiffness,fatigue and wear resistane,and excellent resistane to chemical degradation,has been widely used in many fields.PEEK particles with size 1-2 μm were prepared by multistage sedimentation method,and a series of PEEK-SPEEK composite membranes were prepared by recasting method,then PEEK-SPEEK composite membranes was heated at 370 oC for 30 min,PEEK particles were melted to form a network structure and filled in the S65 Na matrix membrane,the 3D PEEK network reinforced composite membrane(T-PEEK-SPEEK)was obtained.The properties of 3D PEEK network reinforced composite membranes were studied.It was found that the IEC,water uptake,water swelling ratio and proton conductivity of the composite membranes decreased and the mechanical strength increased with the increase of the content of PEEK particles,however,the proton conductivity is higher than 10-2 S/cm,which fully satisfies the application of proton exchange membrane in fuel cell.The effect of DS on the properties of 3D PEEK network reinforced composite membrane was studied.SPEEK(S80Na)with DS of 0.8 was chosen as the matrix membrane and the 3D PEEK network reinforced composite membranes were prepared and compared the performance with composite membranes with S65 Na,it was found that water uptake,water swelling ratio and proton conductivity of composite membranes increased with DS of SPEEK increase.To improve the compatibility between PEEK particles and SPEEK,the modified sulfonated poly(ether ether ketone)particles(sP)was prepared,the S65 Na and S80 Na were selected as polymer matrix membranes,a series of interfacial enhanced 3D PEEK modified SPEEK composite membrane(T-sP-SPEEK)were prepared by recasting method and thermal treament,through the study on the properties of T-sP-SPEEK composite membranes,it was found that the T-sP-SA composite membranes were more compact and smooth than T-PEEK/SPEEK,indicating that s P particles can effectively improve the compatibility with SPEEK.Meanwhile,it was found that the interfacial modification did not affect the dissolution of PEEK particles at high temperature.The composite membranes showed low water swelling behavior and relatively high proton conductivity.Due to the improvement of the interface between the two phases,the composite membranes showed better mechanical strength.The crystal structure of PEEK in the composite membrane was found by XRD analysis.In order to improve the proton conductivity of composite membrane,a series of multi-component SPEEK with carbon nanotubes(CNTs)composite membranes were prepared by recasting method and thermal treament.Improving the swelling resistance and mechanical strength of the SPEEK membrane by using the network structure of PEEK,and improving the proton conductivity by the addition of CNTs.S65 Na was chosen as the matrix membrane,and the CNTs content was 2 wt.%.It was found that the proton conductivity of multi-component SPEEK membrane was improved remarkably with good dimensional stability and excellent mechanical properties as the CNTs were added.The results show that the addition of CNTs can effectively improve the proton conductivity of the composite membrane,meanwhile,the tensile strength of composite membranes was increased and the elongation at break was decreased.This is due to the addition of acidified CNTs increases the compatibility among components so that the tensile strength of composite membranes was increased and the toughness decreased.The XRD spectrum showed that the addition of CNTs had no effect on the formation of PEEK crystalline region.Therefore,the proton conductivity of the composite membranes was greatly increased while mechanical strength was improved.In summary,we proposed an effective and reasonable solutionin based on the properties deficiency of SPEEK membrane the course of research;prepared the binary and termary composite membranes with excellent properties,studied on the properties of the composite membrane,and gave a reasonable explanation for the change of material properties;investigated the influence of phase interface on the material properties,observed and analyzed the microstructure of polymer,and the important factors to improve the composite membrane performance was found.It provides a powerful reference for the large-scale application of SPEEK proton exchange membrane materials.