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Guanghua Zhang - One of the best experts on this subject based on the ideXlab platform.
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influence of side chain structure of Polycarboxylate dispersant on the performance of coal water slurry
Fuel Processing Technology, 2017Co-Authors: Guanghua Zhang, Niu Zhu, Junfeng Zhu, Yurong JiaAbstract:Abstract Two kinds of Polycarboxylate dispersants with different side-chain structures were synthesized with acrylic acid and sodium styrene sulfonate as the main chain, and native starch and methoxyl polyethylene glycol (MPEG1000) as the side chain. Their structures were characterized by FT-IR and 1 H NMR. The dispersants were used for Shenhua coal-water slurry. The optimum amount of dispersant, apparent viscosity, maximum slurry concentration and stability of the slurry were investigated. It was found that economically accessible Polycarboxylate dispersant using starch as the side-chain (PC-St) endowed coal water slurry (CWS) with better dispersibility and stabilizing ability than that of Polycarboxylate dispersant using methoxyl polyethylene glycol as the side-chain (PC1000). When the dosage of PC-St was 0.4 wt%, the maximum concentration of CWS could reach to 66.5%. The dispersing and viscosity-reducing mechanisms of the two dispersants were systematically elucidated through the investigation on the Zeta potential, adsorption, contact angle and X-ray photoelectron spectroscopy (XPS) analysis of coal particles. In comparison with PC1000, the PC-St dispersant had higher saturated adsorption amount on the surface of the coal and was able to provide greater electrostatic repulsion and better wetting effect for coal particles. Moreover, the thickness of the PC-St adsorption layer was 7.57 nm, which provided good steric hindrance to effectively reduce the aggregation among coal particles. It could be concluded that, compared with PC1000 PC-St had better viscosity-reducing ability and dispersibility, as well as stabilizing ability for CWS.
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dispersion performance and mechanism of Polycarboxylates bearing side chains of moderate length in coal water slurries
Fuel, 2017Co-Authors: Junfeng Zhu, Pei Wang, Guanghua ZhangAbstract:Abstract The side chain structures of Polycarboxylates are of great importance for their dispersion performance. The impacts of side chain length (length of polyethyleneglycol PEG, m ranging from 8 to 23) of the Polycarboxylates on their dispersion performances and adsorption behaviors were investigated systematically to clarify the governing dispersing mechanism. The study reveals the length of side chain affects main chain polymerization degree ( DP w ) of Polycarboxylates, density of charge groups and adsorption in coal-water interface. Dispersion performances of Polycarboxylates in coal-water slurry depend on their adsorption density and the adsorption layer thickness on the coal. The shorter side chain is beneficial to increase adsorption density. However, the longer side chain is good for increasing adsorption layer thickness. Specifically, the Polycarboxylate with side chains of moderate length ( m = 11) has the thickest adsorption layer and the highest adsorption density to result in its excellent dispersion performance. This information indicates that a balance between main chain length and side chain length should exist. So the Polycarboxylate with the moderate length ratio of main chain to side chain can be designed as a highly efficient dispersant for low rank coal-water slurries.
Junfeng Zhu - One of the best experts on this subject based on the ideXlab platform.
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influence of side chain structure of Polycarboxylate dispersant on the performance of coal water slurry
Fuel Processing Technology, 2017Co-Authors: Guanghua Zhang, Niu Zhu, Junfeng Zhu, Yurong JiaAbstract:Abstract Two kinds of Polycarboxylate dispersants with different side-chain structures were synthesized with acrylic acid and sodium styrene sulfonate as the main chain, and native starch and methoxyl polyethylene glycol (MPEG1000) as the side chain. Their structures were characterized by FT-IR and 1 H NMR. The dispersants were used for Shenhua coal-water slurry. The optimum amount of dispersant, apparent viscosity, maximum slurry concentration and stability of the slurry were investigated. It was found that economically accessible Polycarboxylate dispersant using starch as the side-chain (PC-St) endowed coal water slurry (CWS) with better dispersibility and stabilizing ability than that of Polycarboxylate dispersant using methoxyl polyethylene glycol as the side-chain (PC1000). When the dosage of PC-St was 0.4 wt%, the maximum concentration of CWS could reach to 66.5%. The dispersing and viscosity-reducing mechanisms of the two dispersants were systematically elucidated through the investigation on the Zeta potential, adsorption, contact angle and X-ray photoelectron spectroscopy (XPS) analysis of coal particles. In comparison with PC1000, the PC-St dispersant had higher saturated adsorption amount on the surface of the coal and was able to provide greater electrostatic repulsion and better wetting effect for coal particles. Moreover, the thickness of the PC-St adsorption layer was 7.57 nm, which provided good steric hindrance to effectively reduce the aggregation among coal particles. It could be concluded that, compared with PC1000 PC-St had better viscosity-reducing ability and dispersibility, as well as stabilizing ability for CWS.
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dispersion performance and mechanism of Polycarboxylates bearing side chains of moderate length in coal water slurries
Fuel, 2017Co-Authors: Junfeng Zhu, Pei Wang, Guanghua ZhangAbstract:Abstract The side chain structures of Polycarboxylates are of great importance for their dispersion performance. The impacts of side chain length (length of polyethyleneglycol PEG, m ranging from 8 to 23) of the Polycarboxylates on their dispersion performances and adsorption behaviors were investigated systematically to clarify the governing dispersing mechanism. The study reveals the length of side chain affects main chain polymerization degree ( DP w ) of Polycarboxylates, density of charge groups and adsorption in coal-water interface. Dispersion performances of Polycarboxylates in coal-water slurry depend on their adsorption density and the adsorption layer thickness on the coal. The shorter side chain is beneficial to increase adsorption density. However, the longer side chain is good for increasing adsorption layer thickness. Specifically, the Polycarboxylate with side chains of moderate length ( m = 11) has the thickest adsorption layer and the highest adsorption density to result in its excellent dispersion performance. This information indicates that a balance between main chain length and side chain length should exist. So the Polycarboxylate with the moderate length ratio of main chain to side chain can be designed as a highly efficient dispersant for low rank coal-water slurries.
Johann Plank - One of the best experts on this subject based on the ideXlab platform.
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novel concrete superplasticizers based on phosphate esters
Cement and Concrete Research, 2019Co-Authors: J Stecher, Johann PlankAbstract:Abstract Novel polyphosphate superplasticizers were synthesized by copolymerization reaction between 2-(methacryloyl oxy) ethyl phosphate monomer and the macromonomer polyethylene glycol methacrylate ester at different molar ratios. The synthesized phosphated comb polymers were characterized by size exclusion chromatography and elemental analysis and their dispersing performance in cement was assessed via mini slump tests in cement paste. The phosphated comb polymers exhibited superior dispersing performance over conventional Polycarboxylate comb polymers (PCEs), were less retarding on cement and showed comparable robustness against sulfate and clay impurities. These properties can be explained by the high calcium complexing capacity of the phosphate groups. Thus, phosphated comb polymers present a viable alternative to Polycarboxylate superplasticizers.
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impact of different types of Polycarboxylate superplasticisers on spontaneous crystallisation of ettringite
Advances in Cement Research, 2016Co-Authors: Markus R Meier, Alexander Rinkenburger, Johann PlankAbstract:The spontaneous crystallisation of ettringite from combined calcium hydroxide (Ca(OH)2) and aluminium sulfate (Al2(SO4)3) solutions was investigated in the presence and absence of three different kinds of Polycarboxylate superplasticisers. The crystallisation period was limited to 10 s only to study the initial crystals, which provide the anchoring sites for most admixtures in cement. It was found that, in the absence of Polycarboxylate polymers, only few, but large (l ∼ 3·5 μm), hexagonal, prismatic ettringite crystals exhibiting numerous defects on their surfaces were formed. However, when Polycarboxylate polymers were present during the crystallisation, then the crystal sizes decreased to ∼ 0·5–2·1 μm. Generally, crystal sizes were found to decrease with increasing specific anionic charge of the same kind of Polycarboxylate polymer. Apparently, polymers exhibiting a higher affinity to the crystal surfaces of ettringite inhibit its growth more strongly and produce smaller crystals. Furthermore, the spec...
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influence of the hlb value of Polycarboxylate superplasticizers on the flow behavior of mortar and concrete
Cement and Concrete Research, 2014Co-Authors: Alex Lange, Tsuyoshi Hirata, Johann PlankAbstract:Abstract Applicators of mortars and concretes admixed with Polycarboxylate superplasticizers routinely observe that at low water-to-cement (w/c) ratios (e.g.
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experimental determination of the effective anionic charge density of Polycarboxylate superplasticizers in cement pore solution
Cement and Concrete Research, 2009Co-Authors: Johann Plank, Bernhard SachsenhauserAbstract:Abstract The specific anionic charge density of Polycarboxylate superplasticizers can be determined experimentally by titration with a cationic polyelectrolyte. In this study, the anionic charge densities of several Polycarboxylates based on methacrylate ester chemistry were measured in aqueous solution at pH 7 and 12.6, resp., and in cement pore solution. The anionic charge of the Polycarboxylates increases with increasing pH value as a result of deprotonation of the carboxylate groups in the polymer backbone. Addition of Ca2+ ions generally causes a decrease of the anionic charge density. The reduction in anionic charge varies and depends on the architecture of the Polycarboxylate. The effect results from the binding of calcium ions by the carboxylate groups, both through complexation and counter-ion condensation. Consequently, the effective anionic charge density of Polycarboxylates in cement pore solution can differ significantly from the charge density which is calculated based on the chemical composition. Generally the –COO− functionality may coordinate Ca2+ as a monodentate or bidentate ligand. The type of coordination depends on the steric accessibility of the carboxyl group. In PC molecules possessing high side chain density, the –COO− group is shielded by the side chains and coordinates as bidentate ligand, producing a neutral Ca2+–PC complex. Accordingly, this type of PC shows almost no anionic charge anymore in cement pore solution. In PCs possessing high amount of –COO−, Ca2+ is coordinated monodentate, resulting in an anionic complex. Consequently, this type of PC shows significant anionic character in pore solution. Its adsorption behaviour is determined by a gain in enthalpy which derives from the electrostatic attraction between the PC and the surface of cement. This way, by utilizing the relatively simple method of charge titration, it is possible to assess the electrostatic attraction which, besides entropy gains, is the driving force behind the adsorption of Polycarboxylates on the cement surface and thus determines their effectiveness as dispersing agent. The findings are generally applicable to other anionic admixtures used in cement.
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novel organo mineral phases obtained by intercalation of maleic anhydride allyl ether copolymers into layered calcium aluminum hydrates
Inorganica Chimica Acta, 2006Co-Authors: Johann Plank, Helena Keller, Philip R Andres, Zhimin DaiAbstract:Abstract The work presented here deals with the intercalation of worm- and brush-shaped Polycarboxylates (PC) into calcium aluminum layered double hydroxide (Ca–Al-LDH). The nanocomposite materials were obtained from tricalcium aluminate hydration in presence of Polycarboxylate copolymers with different side chain lengths. As Polycarboxylate compound, amphiphilic copolymers composed of maleic anhydride and α-allyl-ω-methoxy-poly(ethylene glycol) ether with side chain lengths of n = 7, 10, 34, 70 and 90 ethylene oxide units (EOUs) were chosen. These polymers possess a high side chain density due to strictly alternating copolymerization. Powder X-ray diffraction (XRD) of the synthesized Ca–Al–PC-LDH composites revealed that basal spacings ( d -values) increase with the number n of EOUs in the side chain. An extremely high d -value of 4.85 nm was obtained for the polymer with n = 34 EOUs. According to elemental analysis data, the amounts of organic material present in the different composites were found to lie between 48 and 77 wt.%, respectively. Additionally, IR spectroscopy and thermogravimetric measurements were carried out in order to characterize the intercalates. The layered structure of the organo-mineral materials was confirmed by transmission electron microscopy (TEM).
Yurong Jia - One of the best experts on this subject based on the ideXlab platform.
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influence of side chain structure of Polycarboxylate dispersant on the performance of coal water slurry
Fuel Processing Technology, 2017Co-Authors: Guanghua Zhang, Niu Zhu, Junfeng Zhu, Yurong JiaAbstract:Abstract Two kinds of Polycarboxylate dispersants with different side-chain structures were synthesized with acrylic acid and sodium styrene sulfonate as the main chain, and native starch and methoxyl polyethylene glycol (MPEG1000) as the side chain. Their structures were characterized by FT-IR and 1 H NMR. The dispersants were used for Shenhua coal-water slurry. The optimum amount of dispersant, apparent viscosity, maximum slurry concentration and stability of the slurry were investigated. It was found that economically accessible Polycarboxylate dispersant using starch as the side-chain (PC-St) endowed coal water slurry (CWS) with better dispersibility and stabilizing ability than that of Polycarboxylate dispersant using methoxyl polyethylene glycol as the side-chain (PC1000). When the dosage of PC-St was 0.4 wt%, the maximum concentration of CWS could reach to 66.5%. The dispersing and viscosity-reducing mechanisms of the two dispersants were systematically elucidated through the investigation on the Zeta potential, adsorption, contact angle and X-ray photoelectron spectroscopy (XPS) analysis of coal particles. In comparison with PC1000, the PC-St dispersant had higher saturated adsorption amount on the surface of the coal and was able to provide greater electrostatic repulsion and better wetting effect for coal particles. Moreover, the thickness of the PC-St adsorption layer was 7.57 nm, which provided good steric hindrance to effectively reduce the aggregation among coal particles. It could be concluded that, compared with PC1000 PC-St had better viscosity-reducing ability and dispersibility, as well as stabilizing ability for CWS.
Hao Pang - One of the best experts on this subject based on the ideXlab platform.
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study on the dispersion adsorption and early hydration behavior of cement pastes containing multi armed Polycarboxylate superplasticizers
Journal of Dispersion Science and Technology, 2020Co-Authors: Kun Wang, Jianheng Huang, Hao Pang, Hao Huang, Linxia Song, Yangyang ZhaoAbstract:Multi-armed Polycarboxylate superplasticizers (SPCEs) were prepared via esterification-copolymerization in aqueous media from various polyols (including glycerol, xylitol and mannitol), acrylic aci...
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synthesis and characterization of high performance cross linked Polycarboxylate superplasticizers
Construction and Building Materials, 2019Co-Authors: Xiuju Lin, Bing Liao, Jingfei Zhang, Jianheng Huang, Hao PangAbstract:Abstract Cross-linked sustained-release Polycarboxylate superplasticizers (SPs) are superior alternative to the comb-type Polycarboxylate SPs due to they offer both a high fluidity and a good retention effect for concrete slurry. In this context, a series of cross-linked Polycarboxylate superplasticizers were synthesized using acrylic acid, methylallyl polyoxyethylene ether and four different cross-linkers containing ester groups, respectively. The key difference among these four cross-linkers is their molecular weights because they each possessed the different ethoxy content. The fluidity and fluidity retention tests, adsorption performance and scanning electron microscope tests showed that the cross-linked superplasticizers offered good dispersing effects and excellent slump performance. Excitingly, the maximum flow reached up to 394 mm at a water-cement ratio of 0.35 and this high fluidity could be simultaneously maintained for 2 h, which facilitated concrete transport over long distances, therefore improving the practical workability of concrete. Furthermore, it was found that the superplasticizers derived from cross-linkers with higher ethoxy group contents provided cement paste samples with improved fluidity. Evaluation of the hydration heat and setting time demonstrated that the cross-linked Polycarboxylate superplasticizers could delay the hydration of cement and the final setting time had been extended by 4 h in comparation with blank samples. After 3, 7 and 28 d, the compressive strength of the cement mortar was improved with increases of molecular weight of the cross-linker in the cross-linked superplasticizers due to the elevation of ethoxy content.
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synthesis and performance of a novel amphoteric Polycarboxylate superplasticizer with hydrolysable ester group
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019Co-Authors: Simin Li, Jingfei Zhang, Jianheng Huang, Hao Pang, Yeyun Meng, Bing LiaoAbstract:Abstract A novel hydrolysable cationic monomer of quaternary ammonium dialkyl maleate was synthesized and subsequently copolymerized with acrylic acid and isobutenyl polyethylene glycol to successfully yield an amphoteric Polycarboxylate superplasticizer (APC). The effects of the APC on cement particles were systematically investigated. The fluidity, fluidity retention and mechanical properties were measured to evaluate the performances of the APC and compared with those of a Polycarboxylate superplasticizer (PCE). In addition, X-ray diffraction, thermogravimetric and scanning electron microscopy characterization were performed to investigate the influences of the APC on cement particles from microscopic level. Furthermore, the interactions of the APC with cement particles were also investigated via adsorption, hydration heat and zeta potential measurements. It was found that the introduction of a hydrolysable cationic monomer could improve the micro-structure and delay the hydration of cement. Moreover, the APC could increase the cement paste fluidity and fluidity retention.
