Twice-painting technique was adopted to prepare heavy-duty anticorrosive coating films formed by aqueous latexes of copolymers of vinylidene chloride（VDC） with an acrylate, namely methyl acrylate（MA）, ethyl acryl...Twice-painting technique was adopted to prepare heavy-duty anticorrosive coating films formed by aqueous latexes of copolymers of vinylidene chloride（VDC） with an acrylate, namely methyl acrylate（MA）, ethyl acrylate（EA）, butyl acrylate（BA） or 2-ethylhexyl acrylate（EHA）. Harsh salt-spray corrosion tests demonstrated that the optimized twicepainting technique was that the acidic latex solution was adjusted to p H 5-6 for the first painting, while it was utilized directly for the second painting. The test of 600 h of harsh salt-spray corrosion showed that MA-VDC85 coating could protect the steel excellently, whereas the other acrylate-VDC coatings with 75%-90% VDC content could not protect the steel so effectively. Further corrosion test showed that（1） MA-VDC85 coating protected steel from loss of metallic luster for at least 1000 h of salt-spray corrosion;（2） adhesion of MA-VDC85 coating to steel was excellent for at least 800 h of saltspray corrosion, but became very poor after 1000 h. Differential scanning calorimetry, thermogravimetric analysis, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were used to evaluate the corroded MA-VDC85 film.展开更多
Multiarm star block copolymers hyperbranched polyethylenimine-b-poly（2-hydroxyethyl methacrylate） （HPEI-b- PHEMA） with average 28 PHEMA arms have been prepared by atom transfer radical polymerization （ATRP） of H...Multiarm star block copolymers hyperbranched polyethylenimine-b-poly（2-hydroxyethyl methacrylate） （HPEI-b- PHEMA） with average 28 PHEMA arms have been prepared by atom transfer radical polymerization （ATRP） of HEMA in a mixed solvent of methanol and water using a core-first strategy. The hyperbranched macroinitiator employed was prepared on the basis of well-defined hyperbranched polyethylenimine with Mw/Mn of 1.04 by amidation with 2-bromo-isobutyryl bromide. The polymerization condition was optimized to prepare star copolymers with narrow dispersity, and the variables included the volume ratio of methanol to water, the molar ratio of initiating site to CuC1 and the molar ratio of [CuCl]：[CuBr2]. Under the optimized polymerization condition, the lowest Mw/Mn value of the obtained star copolymers was around 1.3. Kinetic analysis showed that an induction period existed in the polymerization of HEMA. After this induction period, a linear dependence of ln（[M]0/[M]t） on time was observed. The obtained HPEI-b-PHEMA could adsorb hydrophilic molecules. The comparison with the star copolymer with hydrophobic core and hydrophilic PHEMA shell verified that both the hydrophilic core and shell could host the hydrophilic vips, but the amidated HPEI core was more effective than the PHEMA shell.展开更多
基金financially supported by the Program for New Century Excellent Talents in Universitiesthe National Natural Science Foundation of China(No.21074088)
文摘Twice-painting technique was adopted to prepare heavy-duty anticorrosive coating films formed by aqueous latexes of copolymers of vinylidene chloride（VDC） with an acrylate, namely methyl acrylate（MA）, ethyl acrylate（EA）, butyl acrylate（BA） or 2-ethylhexyl acrylate（EHA）. Harsh salt-spray corrosion tests demonstrated that the optimized twicepainting technique was that the acidic latex solution was adjusted to p H 5-6 for the first painting, while it was utilized directly for the second painting. The test of 600 h of harsh salt-spray corrosion showed that MA-VDC85 coating could protect the steel excellently, whereas the other acrylate-VDC coatings with 75%-90% VDC content could not protect the steel so effectively. Further corrosion test showed that（1） MA-VDC85 coating protected steel from loss of metallic luster for at least 1000 h of salt-spray corrosion;（2） adhesion of MA-VDC85 coating to steel was excellent for at least 800 h of saltspray corrosion, but became very poor after 1000 h. Differential scanning calorimetry, thermogravimetric analysis, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were used to evaluate the corroded MA-VDC85 film.
基金financially supported by the Program for New Century Excellent Talents in Universitiesthe National Natural Science Foundation of China (Nos. 21074088, 31201426)
文摘Multiarm star block copolymers hyperbranched polyethylenimine-b-poly（2-hydroxyethyl methacrylate） （HPEI-b- PHEMA） with average 28 PHEMA arms have been prepared by atom transfer radical polymerization （ATRP） of HEMA in a mixed solvent of methanol and water using a core-first strategy. The hyperbranched macroinitiator employed was prepared on the basis of well-defined hyperbranched polyethylenimine with Mw/Mn of 1.04 by amidation with 2-bromo-isobutyryl bromide. The polymerization condition was optimized to prepare star copolymers with narrow dispersity, and the variables included the volume ratio of methanol to water, the molar ratio of initiating site to CuC1 and the molar ratio of [CuCl]：[CuBr2]. Under the optimized polymerization condition, the lowest Mw/Mn value of the obtained star copolymers was around 1.3. Kinetic analysis showed that an induction period existed in the polymerization of HEMA. After this induction period, a linear dependence of ln（[M]0/[M]t） on time was observed. The obtained HPEI-b-PHEMA could adsorb hydrophilic molecules. The comparison with the star copolymer with hydrophobic core and hydrophilic PHEMA shell verified that both the hydrophilic core and shell could host the hydrophilic vips, but the amidated HPEI core was more effective than the PHEMA shell.
