| More attention has been paid to the development and research of the polymer electrolyte membrane fuel cell(PEMFC) by internal and external conuntries, due to its high percent conversion of energy and little pollution. Bipolar plate is one of the most important components of PEMFC, which accounts for 45% and 80% of the stack cost and weight. So, developing new bipolar plate material and reducing its cost and weight can promote the industrialization of PEMFC.Carbon nanotubes(CNTs) reinforced phenol formaldehyde(PF) resin/graphite composite was prepared on the basis of summarizing current reasearch of bipolar plate material and preparation. According to property demand on resin/graphite bipolar plate by Department of Energy (USA), the bending strength and conductivity were considered as major factor during the research. In my research, cheaper graphite and PF resin was used as matrix to reduce the cost of bipolar plate; CNTs was used to reinforce the PF resin/graphite composite to reduce the capacity and weight of bipolar plate. The main research content is as follows:Firstly, PF resin/graphite composite was prepared by low temperature and hot pressure molding formation. The effect of preparation technology on properties of composite was also studied, then the technological parameter of composite was optimized.PF resin/graphite composite was prepared by single-factor test at first. The effect of preparation technology on properties of composite was also studied. The results show that the conductivity decreases and bending strength increase with the increasing of PF resin content; that the effect of molding temprature on prperties of composite is similar to that of molding tempratur, the conductivity vary wave-like and bending strength will increase firstly and then decrease with the increasing of molding temprature and time; that the effect of molding pressure on prperties of composite is similar to that of graphite size, the conductivity and bending strength will increase firstly and then decrease with the increasing of pressure and graphite size; and the best conductivity and bending strength of the composite are 142 s/cm and 61.6 MPa, respectively, when its PF resin content is 15wt% and graphite size is 105 - 150μm molded at 240℃and 30MPa for 60min.Then, orthogonal test was used to keep on optimizing the technological parameter (graphite content, molding temprature and time). The results show that the effect of graphite content on the properties of composite is obvious, the effects of curing temperature and time are not obvious; that the bending strength of composite reduces with the increasing of the graphite content in single-factor and orthogonal test; that the conductivity of composite increases with increasing of graphite content in single-factor test, but it increases firstly and then decreases with the increasing of the graphite content in orthogonal test; that the optimal association of conductivity is that graphite content is 85%, and that molding temprature and time are 260℃and 100min, when its conductivity and bending strength is 171.2 s/cm and 59.7MPa.Secondly, the CNTs reinforced PF resin/graphite composite was prepared, and the effects of CNTs 's surface treatment and content on properties of composite were also studied to get the optimal preparation technological parameters.CNTs were purification treated by air oxydation treatment. The CNTs before and after purification treatment were observed by TEM and DTG, which showes that CNTs after purification are clear and smooth, that CNTs were purified effectively.Then, CNTs were surface treated by Fenton/ ultraviolet(UV), which is the first time to be used in the surface treatment for CNTs, then was used to reinforce the PF resin/graphite composite. The effects of the technological parameters of Fenton/UV on surface of CNTs and properties of composite were also studied, which include the mached between Fe2+ and H2O2, the pH value in Fenton regents and reaction time.Compared with other Fenton regents reaction (Fenton,Fenton/US)by FTIR, Fenton/UV treatment can generate large quantity of hydroxyl groups and a little of carboxyl groups on the sidewall of CNTs, which can improve the interfacial binding between CNTs and matrix, then can improve the properties of composite.The technological conditions are important factors, which can effect the interface bonding between CNTs and matrix. The effects of technological conditions on surface of CNTs and properties of composite were studied by FTIR, XRD. On the basis of it, the best technological conditions are: MFe2+ : MH2O = 1:40, pH=3 and reaction timeis 3h.Then, the effects of CNTs content on the properties of composite were studied. The results show that the conductivity and bending strength increase with the increasing of CNTs in the experiment system; that the best conductivity and bending strength of the composite are 81.2 MPa and 195.4 s/cm when CNTs content is 5wt%, respectively, which improved 36.0% and 14.1% compared with PF resin/graphite composite.Thirdly, the mechanism of Fenton regents reaction treated CNTs was studied by TEM, Raman spectra and FTIR. The results show that hydroxyl radical generated in the Fenton reation can attack the unsaturated bonds C=C on the sidewalls by electrophilic addition reaction, introducing hydroxyl groups on the sidewalls of CNTs; then the hydroxyl groups was oxidized to carboxyl groups by oxidation susceptibility of hydroxyl radical.Fourthly, the reinforcement mechanism of composite were studies by SEM. The results show that the boundary between CNTs and PF rensin is on strong bonding state; that the sticky point and "pull-out" effect of CNTs with skin-core structure is the reinforcement mechanism of composite.Fifthly, the bending strength forecast equation on the CNTs reinforced PF resin/graphite composite was concluded by using composite mechanical theory. The CNTs length cofficient, and CNTs oriental coefficient were considered and their analytic equations were also concluded, and the discreet value is inosculated with the experiment value when CNTs content is lower(<4wt%) for the bending strength of composite.
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