Preparation Of Modified GO And PVDF Blend Films And Its Performance Research

Polyvinylidene fluoride(PVDF),a fluorine-containing polymer material with superior properties,is widely used in fluorine-containing coatings,electrical,electronic,petrochemical fields and so on,which becomes an indispensable polymer material for national development.However,due to the self-hydrophobic nature,PVDF materials may encounter problem of low separation efficiency in practical applications.It has a great influence to modify PVDF to improve the hydrophilic properties and expand application fields in the treatment of wastewater.Graphene oxide(GO)with oxygen-containing functional groups has a good hydrophilicity.It is a good hydrophilic modified filler.However,GO tends to be easily aggregated and has poor compatibility with other materials in practical applications.To solve the above problem,The carboxyl group on the edge as well as the phenolic hydroxyl group and epoxy group on the surface can be used as active sites.GO can be modified by covalent and non-covalent methods to better composite with other materials,further creating excellent composite materials.Therefore,applications of GO would be expanded.In order to improve the compatibility of GO and PVDF materials and improve the hydrophilic performance of PVDF materials,we synthesized Vinylidene fluoride graft polymerization modified graphene oxide(GO-g-PVDF).PVDF and GO-g-PVDF composite membranes(GO-g-PVDF/PVDF)were prepared by physical blending method.Besides,the properties of this material was also investigated.The main research content is as follows:First,commercial graphene powder was oxidized to produce GO using the modified Hummers method.Infrared absorption spectra and thermogravimetry(TGA)tests indicate the GO surface is rich in oxygen-containing groups;X-ray diffraction(XRD)measurements testify that the introduction of oxygen-containing groups increases the distance of the GO interlayers;scanning electron microscopy(SEM)shows the same results as XRD.Then a carboxy-terminated xanthate was synthesized from the reaction of potassium ethylxanthogenate and dibromopropionic acid,and the successful synthesis of carboxyl xanthate was proved by infrared absorption spectroscopy(IR),hydrogen nuclear magneticresonance spectroscopy(NMR)and ultraviolet-visible absorption spectroscopy(UV).Furthermore,xanthate functionalized graphene oxide(GO-Xanthate)was prepared by esterification reaction between abundant hydroxyl groups on the surface of GO and the carboxyl group of carboxy-terminated xanthate.Infrared absorption spectroscopy,elemental energy spectra and thermogravimetry show successful reaction of GO with carboxylate xanthate.X-ray diffraction tests demonstrate that the distances of sheets of GO-Xanthate further increase comparing to normal GO.Subsequently,polyvinylidene fluoride modified graphene oxide(GO-g-PVDF)was prepared by reversible addition-fragmentation chain transfer(RAFT)polymerization of vinylidene fluoride and xanthate groups in GO-Xanthate.Characterization of GO-g-PVDF all confirmed that PVDF was on the graphene oxide sheet by infrared absorption spectroscopy,elemental energy spectrum,and scanning electron microscopy.Also,X-ray diffraction tests showed that the existence of PVDF made the diffraction peaks of the GO disappear.This result showed an unordered stacking state of GO,demonstrating that the GO was completely stripped.Finally,the prepared GO-g-PVDF was applied to the modification of PVDF membrane material.GO-g-PVDF/PVDF composite membrane material was prepared by solution blending,and the material was tested in thermal,mechanical,and hydrophilic aspects.The results show that the thermal decomposition temperature of the composite membrane is 46°C higher than that of the PVDF membrane,and the alkali resistance is also improved.The contact angle of the surface water decreases from 86.3° of the PVDF membrane to 68.1°.The water flux also raised 2.6 times,and membrane maintained a high protein rejection rate.In addition,the tensile strength and rate of elongation at break of the composite film are also significantly better than those of the PVDF original membrane and PVDF/GO blend membrane.The above experimental results show that GO-g-PVDF/PVDF composite membrane material has apparently good potential application in water treatment.