Co-reporter:Ying Yan, Ling Wang, Huiping Zhang, Xinya Zhang
Separation and Purification Technology 2017 Volume 175() pp:213-221
Publication Date(Web):24 March 2017
DOI:10.1016/j.seppur.2016.11.022
•Co-Mn mixed oxides modified ZSM-5/PSSF catalysts were prepared for isopropanol oxidation.•Co/Mn mixed oxides modified ZSM-5/PSSF catalysts showed higher catalytic activity.•Reaction temperature of T90 decreased by 82 °C compared with granular catalyst.A novel gradient porous Co-Mn mixed oxides modified ZSM-5 zeolite membrane/PSSF (paper-like stainless steel fibers) catalyst was prepared for catalytic combustion of isopropanol in a membrane reactor. First, the paper-like sintered stainless steel fibers (PSSF) support was fabricated by wet lay-up papermaking method and sintering process. Then, ZSM-5 zeolite membranes were synthesized on the surface of stainless steel fibers by using secondary growth process. Finally, the cobalt and manganese mixed oxides modified ZSM-5 zeolite membrane catalysts were prepared by wet impregnation method. These novel modified membrane catalysts were characterized by using SEM, XRD, N2 adsorption–desorption isotherms and XPS, respectively. The catalytic activity test was carried out over a membrane reactor filled with ZSM-5 zeolite membrane catalysts and granular catalysts, respectively. The experimental results showed that the junctures of stainless steel fibers were completely sintered together to form a three-dimensional network structure and ZSM-5 zeolite membrane was fabricated on the PSSF support with the thickness of 1.78 μm. The cobalt element existed as Co3+and Co2+, maganese element existed as Mn4+ and Mn3+. The results of catalytic activity tests showed that catalytic activity for isopropanol over ZSM-5 zeolite membrane catalyst was superior to that over granular ZMS-5 catalyst, the reaction temperature of 50% and 90% conversion of isopropanol over ZSM-5 zeolite membrane catalyst dramatically decreased. The Co-Mn(1:4)/ZSM-5/PSSF catalysts presented the most excellent catalytic activity for isopropanol combustion, compared with Co/ZSM-5/PSSF and Mn/ZSM-5/PSSF catalysts, respectively.
Co-reporter:Songshan Jiang, Huiping Zhang, Ying Yan, Xinya Zhang
Microporous and Mesoporous Materials 2017 Volume 240(Volume 240) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.micromeso.2016.11.020
•FeCu-ZSM-5 coating/PSSF catalysts were synthesized for CWPO of phenolic wastewater.•The catalysts exhibited excellent catalytic performance (Xphenol = 100%, XTOC = 61%).•The reaction mechanisms over the membrane catalyst were proposed and discussed.•The synergistic effect of the Cu, Fe component was studied by XPS and H2-TPR.The porous Fe-Cu mixed oxides modified ZSM-5 coating/PSSF (paper-like sintered stainless steel fibers) catalysts were synthesized for the continuous degradation of phenol by means of catalytic wet peroxide oxidation. The catalysts were firstly characterized by XRD, N2 adsorption-desorption, SEM and EDS. Then, the activity of the catalysts was evaluated in a continuous reactor at the temperature of 80 °C under atmospheric pressure. The results indicated that phenol conversion of 100% and H2O2 conversion of 98% was obtained and the phenol can be oxidized into organic acids directly without toxic quinones by-products detected. The increase of Cu element can obviously increase the catalytic activity of FeCu-ZSM-5 coating/PSSF catalyst, and the doped of Cu element can effectively increase the stability of Fe active component. H2-TPR and XPS experiments were further carried out to investigate the interactions of the bimetallic component. Finally, catalytic reaction mechanisms of the phenol degradation over the catalysts were proposed. The excellent catalytic activity of the FeCu-ZSM-5 catalysts was resulted from synergistic effect of the Cu, Fe active component and high contacting efficiency of the ZSM-5 coating/PSSF support.Download high-res image (286KB)Download full-size image
Co-reporter:Jin Hu
Journal of Materials Science 2017 Volume 52( Issue 20) pp:12524-12539
Publication Date(Web):12 July 2017
DOI:10.1007/s10853-017-1372-3
The expansion of the industrial needs of isocyanurate type polyisocyanates and the increasing pressure on reducing free toluene diisocyanate (TDI) monomer content necessitate a highly selective catalyst to ensure a lower free monomer content in the product. A catalyst screening was performed in terms of catalytic activity and catalytic selectivity. Of all the common trimerization catalysts, oligomeric Mannich base (OMB), as a special type of Mannich base catalysts, was synthesized and proved to have the most enhanced selectivity and enough activity for the oligomerization of TDI. The influence of temperature and catalyst concentration on its catalytic reaction was investigated by comparing their reaction rate and reaction selectivity. Dodecanol as a compatibility modifying agent was found to be a co-catalyst of OMB, with a synergistic effect on both the reaction rate and reaction selectivity. The oligomerization process was followed and investigated by gel permeation chromatography (GPC) and isocyanate (NCO) back-titration.
Co-reporter:Yuhui Xie, Mingzhi Chen, Delong Xie, Li Zhong, Xinya Zhang
Corrosion Science 2017 Volume 128(Volume 128) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.corsci.2017.08.033
•Graphene oxide is used to accelerate the zinc phosphating process.•Graphene oxide can modify the morphology of phosphate coating to enhance the corrosion resistance.•The possible mechanism of this accelerating process is proposed.Graphene oxide (GO) is used to accelerate zinc phosphating process on steel. The effect of GO on microstructure and corrosion resistance of phosphate coating is investigated. Experiments show that GO sheets can act as sedimentary beds at the initial stage of phosphating process, which can capture metal ions and thus favor the nucleation of phosphate crystals. When the concentration of GO is optimized to be 1.2 g/L, the phosphate coating possesses the most uniform and compact structure and achieves the strongest corrosion resistance. Results demonstrate that GO can effectively accelerate phosphating process and enhance corrosion resistance of phosphate coating.Download high-res image (133KB)Download full-size image
Co-reporter:Jin Hu;Zhuo Chen;Yong He;Hong Huang
Research on Chemical Intermediates 2017 Volume 43( Issue 5) pp:2799-2816
Publication Date(Web):2017 May
DOI:10.1007/s11164-016-2795-1
Solvent-free hexamethylene diisocyanate (HDI)-based polyisocyanates were prepared by cyclotrimerization of HDI monomer using tri-n-butylphosphine (TBP) as a catalyst, and characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry (MS). The GPC results revealed the effects of reaction time, temperature and concentration of TBP on the molecular weight distribution of the polyisocyanates. The structures of the polyisocyanates were identified and confirmed by the combined analysis of MS, FTIR and NMR. There are dimer, pentamer, heptamer and higher-molecular-weight oligomers presented in the product, beyond the main product of trimer oligomers.
Co-reporter:Yuhui Xie, Xinxin Sheng, Delong Xie, Zixian Liu, Xinya Zhang, Li Zhong
Carbon 2016 Volume 109() pp:673-680
Publication Date(Web):November 2016
DOI:10.1016/j.carbon.2016.08.079
The porous graphene hydrogels (GHs) are of particular interest in various applications, such as energy-storage devices, catalyst and sensors. In this paper, GHs with controllable pore structure are prepared from graphene oxide (GO) aqueous dispersion by a facile chemical reduction method. The pore size distribution (PSD) and specific surface area (SSA) of GHs can be regulated by adjusting the pH value of GO dispersion. It is found that both the pore size and SSA of GHs gradually increase with the pH value of GO dispersion. For the GH prepared at pH = 1.65, the PSD has one peak at 1.83 nm with a SSA of 723.35 m2/g. As the pH value increases to 11.73, the peak moves to 3.2 nm and the SSA keeps rising to 1107.24 m2/g. Rheological measurements show that both the storage modulus and yield stress of the GHs decrease with the increasing pH value. Electrochemical evaluation of GHs as the electrodes of supercapacitors reveals that the specific capacitance reaches the highest value for GH prepared at pH = 5.25, which has a specific pore structure, showing the coexistence of large (3.2 nm) and small pores (1.89 nm).
Co-reporter:Delong Xie, Xiaolin Ren, Yuhui Xie, Xinya Zhang, and Shijun Liao
ACS Macro Letters 2016 Volume 5(Issue 2) pp:174
Publication Date(Web):January 13, 2016
DOI:10.1021/acsmacrolett.5b00852
Red blood cell (RBC)-like particles have shown great interest as a model for the understanding of the cell behavior and as promising biomaterials in targeted drug delivery. In this study, a simple and versatile route was proposed for the large-scale synthesis of monodisperse and well-defined RBC-like PS particles using divinylbenzene (DVB) as the cross-linker and ethanol as reaction medium. RBC-like particles were obtained due to the asymmetric shrinkage of a cross-linked network during the phase separation process. An ordered self-assembly monolayer with the concave facing up at the air–water interface was also demonstrated.
Co-reporter:Xinxin Sheng, Wenxi Cai, Li Zhong, Delong Xie, and Xinya Zhang
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 31) pp:8576
Publication Date(Web):July 20, 2016
DOI:10.1021/acs.iecr.6b01975
Functionalized graphene (PGO)/polyaniline (PANI) nanocomposites with effective synergistic reinforcement on anticorrosion have been prepared via an in situ redox polymerization–dedoping technique. PGO nanosheets are obtained through the modification of graphene oxide with p-phenylenediamine to improve the dispersion stability in acidic conditions and compatibility with the polymer. Also, PGO/PANI composites are synthesized via the in situ redox polymerization of aniline. The results show that PGO is highly exfoliated and intercalated among the PANI matrix. In potentiodynamic polarization tests, the anticorrosion efficiency of the films with reinforcement of PGO/PANI composites increases from 85.16% to 99.98%. Moreover, the lowest corrosion rate is 1.68 × 10–4 mm/year, which is much better than that with individual PGO or PANI. Electrochemical impedance spectroscopy, where the Warburg impedance component emerges, further reveals that well-dispersed PGO in the film can retard or defend permeation of the corrosive material from the environment.
Co-reporter:Chunling Wang, Xinxin Sheng, Delong Xie, Xinya Zhang, Huiping Zhang
Progress in Organic Coatings 2016 Volume 101() pp:597-603
Publication Date(Web):December 2016
DOI:10.1016/j.porgcoat.2016.10.007
•The TiO2/P (MMA/BA/MAA) nanocomposite latex are successfully prepared by miniemulsion polymerization.•TiO2 nanoparticles are monodispersed in the latex particles, almost no aggregation occurs during the film formation process.•The thermal properties of the nanocomposites are enhanced significantly.•The nanocomposite film possesses excellent UV-shielding capacity and exhibits high visible transparency.High performance TiO2/polymer nanocomposites with enhanced thermal and excellent UV-shielding properties have been successfully prepared by means of the anatase TiO2 nanoparticles homogeneously dispersed in the poly (methyl methacrylate/butyl acrylate/methacrylic acid) [P (MMA/BA/MAA)] matrix via a miniemulsion polymerization process. Highly crystalline TiO2 nanoparticles with 5–8 nm diameter, were synthesized by a non-aqueous process and then modified with γ-Methacryloxypropyltrimethoxysilane (A174) to improve the compatibility with polymer. FTIR, TGA and dispersity tests in monomers/water verify that the A174 is chemically bonded onto the surface of TiO2 nanoparticles. TEM, SEM and EDS analyses indicate that the TiO2 nanoparticles are homogeneously dispersed in the polymer matrix. TGA and DSC studies confirm that the thermal properties of the resultant nanocomposites are significantly enhanced with respect to the neat polymer. UV–vis transmission spectra results reveal that the films with TiO2 nanoparticles has an excellent UV-shielding property, even at 1.5 wt% TiO2 nanoparticles loading can almost block the UV light below 350 nm while still having a high visible transparency. Therefore, the resultant nanocomposite films could be used as transparent UV-shielding materials.
Co-reporter:Delong Xie;Xiaolin Ren;Shijun Liao
Journal of Nanoparticle Research 2016 Volume 18( Issue 3) pp:
Publication Date(Web):2016 March
DOI:10.1007/s11051-016-3379-0
Raspberry-shaped composite particles with polystyrene (PSt) as core and poly(n-butyl acrylate-co-acrylic acid) (P(BA–AA)) as corona were synthesized via emulsion polymerization. The random copolymer, P(BA–AA), was pre-prepared and used as a polymeric surfactant, its emulsifying properties adjusted by changing the mass ratio of BA and AA. The morphology of the resulting core–corona composite particles, P(St/P(BA–AA)), could be regulated and controlled by varying the concentrations of P(BA–AA) or the mass ratio of BA:AA in P(BA–AA). The experimental results indicate that 3.0–6.0 wt% of P(BA–AA) is required to obtain stable composite emulsions, and P(BA–AA) with a mass ratio of BA:AA = 1:2 is able to generate distinct core–corona structures. A mechanism of composite particle formation is proposed based on the high affinity between the PSt core and the hydrophobic segments of P(BA–A). The regular morphology of the colloidal film is expected to facilitate potential application of core–corona particles in the field of light scattering. Furthermore, the diversity of core–corona particles can be expanded by replacing P(BA–AA) corona particles with other amphiphilic particles.
Co-reporter:Songshan Jiang, Huiping Zhang, Ying Yan and Xinya Zhang
RSC Advances 2015 vol. 5(Issue 51) pp:41269-41277
Publication Date(Web):30 Apr 2015
DOI:10.1039/C5RA05039A
Stability and deactivation of Fe-ZSM-5 zeolite catalyst for catalytic wet peroxide oxidation (CWPO) of phenol were studied in a membrane reactor. Firstly, the Fe-ZSM-5 zeolite membrane catalyst was prepared by a paper-making/sintering process, secondary growth process and incipient wetness impregnation method. And the influence of residence time on the CWPO of phenol was evaluated by modifying the catalyst bed height. Then, stability of the Fe-ZSM-5 zeolite membrane catalyst was studied by the long-term experiment (40 hours). Finally, the deactivation mechanisms of the Fe-ZSM-5 zeolite membrane catalyst were investigated by N2 adsorption–desorption, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermal gravimetric (TG) analysis, Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, respectively. The results of CWPO of phenol showed that complete phenol conversion with a high TOC conversion (about 60%) was obtained at the catalyst bed height of 4 cm. Meanwhile, good stability with low Fe leaching concentration (about 0.5 mg L−1) and high phenol conversion (above 85%) were obtained after continuously running for 40 hours. Furthermore, the loss of active component, the partial phase change of Fe2O3, the crystallinity change of the ZSM-5 zeolite membrane and the coke formation on the surface of the catalyst were found to be responsible for the deactivation of the catalyst.
Co-reporter:Wang Ling, Zhang Huiping, Yan Ying and Zhang Xinya
RSC Advances 2015 vol. 5(Issue 37) pp:29482-29490
Publication Date(Web):20 Mar 2015
DOI:10.1039/C4RA15730C
Manganese oxide modified ZSM-5 membrane catalysts were prepared for the catalytic combustion of a volatile organic compound (isopropanol) over a zeolite membrane reactor. Characterization of all samples was carried out by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS) and H2-temperature programmed reduction (H2-TPR). The performance of the catalytic oxidation of a single VOC (isopropanol) was investigated over the zeolite membrane reactor based on Mn/ZSM-5/PSSF catalysts, the experimental results showed that the 0.5 M Mn/ZSM-5/PSSF-350 °C catalyst exhibited the best catalytic activity for isopropanol oxidation with 90% conversion of isopropanol at 222 °C with a feed concentration of 4.5 mg L−1 and GHSV of 7643 h−1, which was much lower than that of granular Mn/ZSM-5 catalyst (297 °C). The results of a reaction stability test revealed that the Mn/ZSM-5/PSSF catalysts possess excellent reaction stability for isopropanol oxidation for 50 h, and the conversion of isopropanol remained above 97% at 280 °C with a feed concentration of 4.5 mg L−1 and GHSV of 7643 h−1.
Co-reporter:Xinxin Sheng, Delong Xie, Wenxi Cai, Xinya Zhang, Li Zhong, and Huiping Zhang
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 2) pp:649-658
Publication Date(Web):December 22, 2014
DOI:10.1021/ie5035978
The incorporation of graphene nanosheets (GNSs) into a polymer matrix can effectively enhance its thermal and mechanical properties. We report a facile and eco-friendly method for preparing polymer nanocomposites with homogeneously dispersed GNSs in the poly(methyl methacrylate) (PMMA) matrix via first grafting functionalized graphene oxide (GO) using PMMA miniemulsion, then melt blending the grafted GO with PMMA matrix, and simultaneous in situ thermal reduction of GO in the matrix. The results show that the GNSs exhibit exfoliated morphology and good distribution in the obtained nanocomposites. A 37.9% enhancement in tensile strength and a 61.4% increase of Young’s modulus with respect to the polymer matrix are achieved by incorporating only 1.5 wt % GNSs loading. The experimental derived Young’s modulus agrees well with the theoretical simulation. Moreover, the storage modulus of the nanocomposites increases by 45%, while the glass transition temperature (Tg) increases by 7.5 °C at 1.5 wt % GNSs loading.
Co-reporter:Delong Xie;Kai Liao;Lining Wang
Colloid and Polymer Science 2015 Volume 293( Issue 7) pp:1937-1944
Publication Date(Web):2015 July
DOI:10.1007/s00396-015-3568-x
The modified acrylate redispersible polymer powders were obtained in a free-flowing form by spray drying the structured latex. The latex with configuration of soft-core and hard-shell was produced by emulsion polymerization, where methyl methacrylate (MMA) and butyl acrylate (BA) were used as comonomers, methacrylic acid (MAA) as functional monomer. The latex was modified by adipic dihydrazide (ADH) to lower the minimum film-forming temperature (MFFT), and it was found that the MFFT of the latex decreased as the content of ADH increased. The obtained latex was transformed into redispersible polymer powders by spray drying, where the silica-sol was used as anticaking agent. Transmission electron microscopy (TEM) was used to detect the distribution of silica sol in the latex before spray drying, and a raspberry morphology was found. Meanwhile, zeta potential showed that the polymer/silica system was rather stable. After spray drying, the morphology of the polymer powders and the distribution of silica were characterized by SEM and EDS. It indicated that the polymer powders had a standard spherical shape with silica-rich surface. The polymer powders could be redispersed in water with the properties similar to the “mother” latex; SEM showed that the redispersion formed a dense and smooth film at 25 °C.
Co-reporter:Jishuai Guo;Yong He;Delong Xie
Journal of Materials Science 2015 Volume 50( Issue 17) pp:5844-5855
Publication Date(Web):2015 September
DOI:10.1007/s10853-015-9134-6
Toluene diisocyanate (TDI)-based polyisocyanate prepolymer was prepared via TDI self-polymerization with different catalysts at various temperatures. The self-polymerization process was followed by gel permeation chromatography to investigate the formation of individual components. The contents of isocyanate group (–NCO) and free TDI monomer were monitored to confirm the transformation of individual components through back-titration and gas chromatography, respectively. A step-growth polymerization mechanism for TDI-based polyisocyanate reaction was proposed. Simultaneously, a mathematical model was established to simulate the contents of all components in the self-polymerization process, and the simulated data were in good agreement with the experimental results. Mass spectrometry, Fourier transform infrared spectroscopy and 13C nuclear magnetic resonance spectroscopy were employed to identify and confirm the chemical structures of the polyisocyanate prepolymer. The experimental results indicate that several oligomers containing trimer, pentamer, heptamer and higher-molecular-weight oligomers presented simultaneously and interacted with each other. The desired content of each component in TDI-based polyisocyanate prepolymer could be obtained by controlling the reaction conditions.
Co-reporter:Yong He, Xinya Zhang, James Runt
Polymer 2014 Volume 55(Issue 3) pp:906-913
Publication Date(Web):12 February 2014
DOI:10.1016/j.polymer.2014.01.001
Three diisocyanates with different symmetry and planarity (2,6-TDI, 2,4-TDI and MDI) were used to synthesize polyureas with the same oligomeric polyetheramine having a molecular weight of ∼1000 g/mol. The influence of diisocyanate symmetry on the phase separated morphology, hydrogen bonding behavior, and molecular dynamics were investigated. Symmetric diisocyanate structures facilitated self-assembly of hard segments into ribbon-like domains, driven by strong bidentate hydrogen bonding. The hard domains for the 2,6-TDI polymer appear to be continuous in AFM images, while the persistence length of the hard domains in the 2,4-TDI and MDI polymers gradually decrease, and fewer hard domains are apparent with decreasing hard segment symmetry. The extent of hard/soft segment demixing, assessed from small-angle X-ray scattering, was very incomplete for all of the polyureas and is significantly influenced by hard segment structure. For the 2,4- and 2,6-TDI polyureas, two segmental relaxations were observed using dielectric relaxation spectroscopy; one arising from relatively unrestricted motion in the soft segment rich phase, and a slower process associated with segments in the soft phase constrained by their attachment to hard domains.
Co-reporter:Yong He;Delong Xie
Journal of Materials Science 2014 Volume 49( Issue 21) pp:7339-7352
Publication Date(Web):2014 November
DOI:10.1007/s10853-014-8458-y
The structure–morphology–property relationship of thermoplastic polyurethanes and polyureas was reviewed. The effect of hard segment structure and chemistry, and the hydrogen bonding on the morphology and properties of polyurethanes elastomers was presented. Special attention was made on polyureas with strong bidentate hydrogen bonding, and they are important candidates for thermoplastic elastomers with processibility by careful selection of the hard segment symmetry and hydrogen bonding capacity.
Co-reporter:Wenxing Yang, Delong Xie, Xinxin Sheng, and Xinya Zhang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 37) pp:13466-13476
Publication Date(Web):2017-2-22
DOI:10.1021/ie401542d
Nonuniform latex particles, with a gradient change in composition between molecular chains, were prepared using a power-feed technique. The feed program of the addition process was quantitatively analyzed, and the corresponding equations were derived. A simple dropwise analysis model was established to simulate the sequence distribution and cumulative composition of gradient latex particles based on traditional free radical copolymerization. This model avoided consideration of the detailed kinetic procedure with great uncertainties in an emulsion polymerization. The apparent reactivity ratio of methyl methacrylate (MMA) and n-butyl acrylate (BA) during the emulsion copolymerization process, which was first measured by utilizing K-T, YBR, and other methods, and together with the conversion function, were used as the model parameters. 1H NMR and 13C NMR were used to characterize the experimental sequence distribution and cumulative composition to verify the model. The simulation results are in good agreement with the experimental data, and the model shows great tolerance to reactivity ratios calculated by different methods.
Co-reporter:Yong He;Xinfang Zhang;Hong Huang;Jie Chang ;Huanqin Chen
Journal of Applied Polymer Science 2013 Volume 127( Issue 3) pp:2176-2183
Publication Date(Web):
DOI:10.1002/app.37779
Abstract
Reaction kinetics of dropwise addition of trimethylolpropane (TMP) to toluene diisocyanate (TDI-80) at various temperatures and initial stoichiometry was studied. The progress of the polymerization reaction was monitored by measuring the concentration of isocyanate groups and TDI isomers by means of backtitration and high performance liquid chromatography (HPLC), respectively. The kinetics of dropwise addition method, compared with the conventional one-shot method, was well described by a second order equation. This procedure was optimized by comparing the deviations between experimental data and theoretically calculated data. The effects of temperature, initial stoichiometry and TDI isomers on the amount of excess 2,4-TDI and 2,6-TDI were investigated. Three commercially available TDI mixtures, 65 : 35, 80 : 20, and 100 : 0 ratio of 2,4-TDI/2,6-TDI, respectively, were used. A recycling model of unreacted TDI isomers and solvent was established to reach a stable process and yield polyurethane prepolymer with good reproducibility. This model has been applied in the chemical plant to prepare polyurethane prepolymer with precisely defined chemical compositions in a continuous process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Xinya Zhang;Yanhong Liu;Hong Huang;Yongjin Li ;Huanqin Chen
Journal of Applied Polymer Science 2012 Volume 123( Issue 3) pp:1822-1832
Publication Date(Web):
DOI:10.1002/app.34660
Abstract
Self crosslinkable core-shell polyacrylate latices (PAs) cured at ambient temperature were synthesized by semicontinuous-seeded emulsion polymerization with diacetone acrylamide (DAAM) and adipic dihydrazide (ADH) as crosslinkable monomers. The influences of DAAM monomer mass content, neutralizer, and curing temperature on the properties of self crosslinkable core-shell latices and the keto-hydrazide crosslinking were discussed. The spectroscopic techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle instruments were used to determine the structure and properties of PAs. The water evaporating rate during the film-forming process of self crosslinkable core-shell latices was also investigated. FTIR analyses demonstrate that the keto-hydrazide crosslinking reaction does not occur in the latex environment but occurs at ambient temperature with the evaporation of water during the film-forming process. The results of DSC show that the core-shell crosslinkable PAs have two glass transition temperatures (Tg), and Tgs of crosslinked film are higher than that of non crosslinked fim. Moreover, the keto-hydrazide reaction is found to be acid catalyzed and favored by the loss of water and the simultaneous decrease in pH arising from the evaporation of ammonia or amines during film-forming process. Hence, in the volatile ammonia or amines neutralized latices, the latex pH value adjusted to 7–8, which not only ensure the crosslinkable latex with good storage stability but also obtain a coating film with excellent performances by introducing the keto-hydrazine crosslinking reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Wenbin Yan;Yanan Zhu;Huanqin Chen
Iranian Polymer Journal 2012 Volume 21( Issue 9) pp:631-639
Publication Date(Web):2012 September
DOI:10.1007/s13726-012-0068-4
The zinc ion self-crosslinkable polyacrylate latexes (PAs) cured at room temperature were synthesized by seeded semi-continuous emulsion polymerization with zinc oxide (ZnO) as crosslinker. The ZnO and methacrylic acid (MAA) mass contents, method of ZnO introduction in relation to the degree of crosslinking, and the properties of self-crosslinkable latices are examined and discussed. The characterization techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA) have been used to determine the structure and properties of PAs. The experimental results show that in a certain range, the average particle size decreases with an increase in the content of MAA, while the latex stability is undoubtedly improved. The optimum mass content of MAA is 12 % of the total monomers. The optimum amount of ZnO needed is 25 % (mole fraction) of MAA, and the optimum temperature of ZnO introduction is 60 °C. TEM analyses show that the latex particles are coarse spherical particles with surface enriched with comprising abundant carboxyl groups, and zinc ions are dissociated as zinc ammine complex in the aqueous phase. FTIR analyses confirm that the chelate crosslinking occurs between zinc ions and carboxylic acid during the film-forming process. The DSC results indicate that the glass transition temperature (Tg) of PAs increases as a function of the formation of a coordinate structure, and the obtained film exhibits excellent initial hardness and sandability. TGA analyses demonstrate that the introduction of ZnO evidently enhances the thermal stability of self-crosslinkable PAs.
Co-reporter:Xinya Zhang;Xia Wei;Wenxing Yang
Journal of Coatings Technology and Research 2012 Volume 9( Issue 6) pp:765-774
Publication Date(Web):2012 November
DOI:10.1007/s11998-012-9422-x
In this study, gradient acrylate latex particles were synthesized by gradient copolymerization. n-Butyl acrylate (BA) and methyl methacrylate (MMA) were used as co-monomers, dodecyl diphenyl ether sodium disulfonate as the emulsifier, and potassium persulfate as the initiator. The technique involved the continuous addition of one monomer mixture into a stirred tank containing another monomer mixture. Their microstructure and properties were analyzed by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), atomic force microscopy (AFM), transmission electron microscopy (TEM), and particle size analysis. 1H-NMR spectra show a gradual change in the chemical composition with the growth of molecular chains. The gradient polymer latexes, the instantaneous copolymer composition of which varies as the polymerization proceeds, are obtained. GPC analyses show that the aggregated molecular chain in the BA-centered latex particle experiences a process from dominant BA to MMA with changes in the monomer's feed composition during the polymerization. Particle size and TEM analyses show that the increasing latex size agrees well with the gradient growth pattern. DSC analyses show that the gradient latex particles exhibit only one broadened and ambiguous glass transition region. AFM analyses indicate no obvious microphase segregation occurs in the gradient latex particles, further verifying that the gradient microstructure is obtained.
Co-reporter:Xin-ya Zhang 张心亚;Zhi-juan Sun 孙志娟
Journal of Central South University 2007 Volume 14( Issue 5) pp:666-672
Publication Date(Web):2007 October
DOI:10.1007/s11771-007-0128-7
Acrylate latex modified by vinyl triisopropoxy silane (C-1706) was synthesized by seeded emulsion polymerization with anionic emulsifier sodium dodecyl sulphonate(SDS) and nonionic emulsifier OP-10 as the multiple emulsifiers at (78±2)°C. The effects of different factors, such as the emulsifier, C-1706 monomer and its feeding manner on the properties of acrylate latex modified by C-1706 were investigated. The particle size distribution and the structure, the configuration, the weather durability and stain resistance of copolymer latex were characterized by particle size analyzer, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope(TEM), scanning electron microscope(SEM) and ultraviolet aging instrument respectively. The results show that SDS to OP-10 as multiple emulsifiers can lead to coordinated efficiency, the optimal emulsifier dosage is 2.4%–3.2% (mass fraction), and the mass ratio of SDS to OP-10 is 1:1–1:2. The seeded emulsion polymerization can effectively introduce a organic-siloxane bonding in a macromolecule inter polymer, and the obtained acrylate latex modified by organic-siloxane possesses narrow distribution of particle size with mean diameter of 51.8–76.6 nm and has the excellent properties in weather durability and stain-resistance especially.
Co-reporter:Huifang Shen, Xiaolin Du, Xiaolin Ren, Yuhui Xie, Xinxin Sheng, Xinya Zhang
Reactive and Functional Polymers (March 2017) Volume 112() pp:53-59
Publication Date(Web):March 2017
DOI:10.1016/j.reactfunctpolym.2017.01.006
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![Phenol,4,4'-(1-methylethylidene)bis[2,6-bis[(dimethylamino)methyl]-](http://img.cochemist.com/ccimg/16300/16224-36-5_b.png)
