| Waterborne epoxy resin emulsion not only has the advantages of binding force,chemical resistance,anti-corrosion,water tolerance,heat endurance,but also is economy-practising and environmental-friendly.Naturally,it is the hot topic and development direction of the emulsion research for painting.In this thesis,the epoxy resin was modified waterbornely and functionally by using polyethylene glycol(PEG),phosphate ester(PM1500),methacrylic acid(MAA),then the waterborne epoxy resin emulsion was obtained.This thesis first used PEG to modify epoxy resin to get modified epoxy resin(EP20).The hydroxy was brought into the molecular chains of epoxy resin in order to enhance the hydrophilia of epoxy resin.Then,with the certain proportion of EP20 and epoxy resin,they were compounded for further use.Besides,on the basis of MAA and PM1500 as functional monomer,the carboxyl and phosphate group were brought into the molecular chains of epoxy resin by grafting,which aims to improve the hydrophility of epoxy resin and enhance the ability of anti-corrosion of the emulsion.After salification of neutralization,the stable waterborne epoxy resin emulsion was prepared via phase inversion.The research contents of this thesis are as follows:Part one,this thesis had done experiments on how technological conditions including the molecular weight of PEG,the molecular weight of epoxy resin,the choice and dosage of catalyst,reaction temperature,reaction time had influenced the product.The results showed that the intermediate molecular weight of PEG2000 was chosen to modify the epoxy resin E20,whose dosage was applied in proportion of n(epoxy group):n(-OH)=1:1,boron fluoride ethyl ether was functioned as catalyst with the mass of 3%of E20,the reaction temperature was 90℃,and the reaction time was 6 hours.Through the test of solubility,the analysis of fourier transform infrared spectroscopy(FTIR)and the analysis of gel permeation chromatography(GPC),the etherification reaction of PEG2000 and E20 was approved firstly.And EP20 which included at least a molecular chain of E20 and a molecular chain of PEG2000 has good hydrophilicity.Part two,this thesis had done experiments on how technological conditions including the proportion of EP20 and E20,the choice and dosage of solvent,reaction temperature,reaction time and neutralization had influenced the product.The results showed that the waterborne epoxy resin emulsion with the appropriate property could be made when the proportion of m(E20)and m(EP20)was 1:2,the propylene glycol monomethyl ether(PM)and acetone function as solvent,the mass ratio of the mixed solvent and E20 was 15:16,the reaction temperature was 80 ℃,the reaction time was 6 hours and the neutralization was 45%.Part three,the influences of benzoyl peroxide(BPO)as an initiator,MAA as a functional monomer and PM 1500 as a functional monomer on the properties of water-based epoxy resin emulsion were investigated.The results showed that with the increase of BPO dosage,water-based epoxy resin emulsion particle size and polymer dispersity index(PDI)decreased first and then increased,the emulsion viscosity increased first and then decreased.With the increase of MAA dosage,epoxy resin emulsion particle size,PDI and surface tension decreased first and then increased.The water absorption rate of latex film increased with the increase of the dosage of MAA.With the increase of PM1500 dosage,epoxy resin emulsion particle size and PDI decreased.The surface tension of the emulsion decreased first and then increased.The anti-flash rust was gradually extended.The addition of PM1500 had obviously improved the wet adhesion of emulsion.When the amount of BPO was 4%,MAA dosage was 19%and PM1500 was 19%,the emulsion whose particle size was 116.67 nm and PDI index was 0.083 had small particle size,good dispersion,moderate viscosity,good wet adhesion,good anti-flash performance and high stability,and the morphology of latex particles was almost spherical.Part four,the effects of curing agent(WH260)dosage,curing temperature and curing time on the properties of the film were investigated.Scanning electron microscopy(SEM)and electrochemical test on the film were performed.The results showed that when the dosage of WH260 was 17%,the curing temperature was 110℃,the curing time was 4 hours,the film was cured completely.The surface of the film was smooth,without obvious defects.The water resistance,adhesion,impact resistance and toughness of the film were good.In the initial stage of immersion,the corrosion potential(Ecorr)of the film electrode in 3.5%NaCl solution was-0.602 V,which was larger than the Ecorr of the metal electrode.The film played a good protective effect on metal electrodes.With the prolongation of immersion,the Ecorr and the polarization resistance(Rp)of the film electrode gradually decreased,and the corrosion current(Icorr)and the corrosion rate of the film electrode gradually increased.The film electrode was gradually corroded.After immersing for 336 hours,the Ecorr of the film electrode dropped to-0.923 V,the Rp decreased to 3362 Ω,and the Icorr rose to 3.499X10-6 A/cm2.Compared with the metal electrode,the Ecorr and Rp of the film electrode Were slightly larger,and the Icorr reached the same level.The protective effect of the film on the metal electrode had failed. |
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