Preparation And Properties Of The New Anion-exchange Membranes

Fuel-cell is considered to meet the needs of energy and environmental requirements of one of the ideal power source,which have the conveniences of storage,transportation and supplement.It is expected to find wide application as a portable or mobile power,exemplified by battery for cellular phones or engine for electric vehicles,Research of Fuel cell is currently facing two main difficulties.First,the high-transmission of methanol from the anode to the cathode is high,that is,the film's poor performance of alcohol resistance. Second,the anodic catalyst have low activity for methanol oxidation reaction.The oxidation rate of methanol in alkaline medium is higher than in acid medium.The structural sensitivity of Methanol oxidative catalyst is small. And there is also no poisoning phenomenon between the intermediate and electrode catalyst.In alkaline medium,the transfer direction of hydroxyl ion and hydrogen proton transfer is opposite.Thus it can eliminate the methanol permeability produced by electrodialysis.Furthermore,it can reduce the penetrative rate of methanol and so on.Alkaline direct methanol fuel cell is expected to change the environmental of the battery to overcome the two main problemsAs a basic key components of direct methanol fuel cell,anion-exchange membrane can conduct hydroxyl ion,separate fuel and oxidizer.In this paper, our experiments concentrate on the preparation and characterization of the film,and some progresses are obtained as follows:Poly vinylbenzyl chloride(PVBC1) is a kind of preparation for a new type of membrane material,which has a high glass transition temperature, good solubility,film-forming,mechanical properties and chemical stability.The appropriate solvent polymer dissolved PVBCI made of polymer solution,selecting a suitable cross-linking agent added in the polymer solution for cross-linking.Solution will be cast on the formation of a slide,and then let the solvents volatilize at room temperature for long enough time(4 hours) to ensure that the solvents can volatilize completely.Through solution casting method,we can successfully prepared complete PVBC1 ion-exchange membrane,which have the characters of dimensional stability,smooth surface quality,and transparent color.The PVBC1 membrane mechanical properties and the exchange of properties were studied.The solvent,the carrier,the concentration of polymer,cross-linking agent and amount of film-forming properties were analyzed.The moisture content of the film and the ion exchange capacity(IEC) were characterized.Group contribution method used to calculate the solubility parameters of the membrane material PVBC1.The turbidity titration measured value is similar to it.We can get polymer solubility parameters by group contribution method and turbidity titration.For it EA is good solvent for membrane material PVBC1..LCP will be used to study the relationship between the respective casting solution system between PVBC1/NMP/Nonsolvent and PVBC1/EA/ Nonsolvent.Through the experiment of non-solvent additions (H₂O,is butanone,ethylene glycol and glacial acetic acid,n-butyl alcohol and PEG400) in casting solution of the separate system:The resultes show that the relationship of LCP can be used to describe the system of separation. According to the LCP linear curve,intercept a non-solvent precipitation is inversely proportional.The results showed that the ability of precipitation of polymer non-solvent(H₂O,butanone,ethylene glycol and glacial acetic acid, n-butyl alcohol and PEG400) is weakened in turn.The results of calculation and experiment are same.This casting solution system used H₂O as a gel medium.The degree of cross-linked gradually becomes larger during the course of cross-linking reaction.The pace of change continues in a fairly long period. From the analysis of the mechanism of cross-linking,reaction may be Sn1.It is also possible the Sn2.Through experimental determination,in the middle of reaction,we get a series of apparent reaction,n = 1.93,to prove the cross-linking reaction is a mix of Sn1 and Sn2 mechanism of the reaction,the reaction of Sn2 has more chances.But the response rate and time mapping the latter was slowed.The reaction is the existence of solvent-well,that is,the spread of the latter reaction is the key to the process.After cross-linking,Tg became higher.After the cross-linked,polymer membrane became orderly local.