In this work, melamine-formaldehyde resin was cationized by adding modifiers so that the fibers closely bonded to improve their usability and the wet strength of paper was greatly improved. Triethanolamine and dimethy...In this work, melamine-formaldehyde resin was cationized by adding modifiers so that the fibers closely bonded to improve their usability and the wet strength of paper was greatly improved. Triethanolamine and dimethylamine were added to modify the melamine-formaldehyde resin,respectively.The mechanism of the cationized resin was explored and the possible chemical reactions were deduced. It was concluded that,with the use of triethanolamine,the most optimum product was obtained by hydroxymethylation for 30 min with a temperature of 85℃ and p H of 9. 0 where n( melamine) ∶ n( formaldehyde) ∶ n( methanol) ∶ n( triethanolamine) was 100 ∶ 330 ∶ 450 ∶ 15. With the combined use of dimethylamine and methanol,the optimal product was acquired by condensation for 30 min at a temperature of 50℃ and p H of 2. 0 at melamine, formaldehyde, methanol, and dimethylamine molar ratio of100∶ 330∶ 350∶ 20. With the only use of dimethylamine,the optimal product was obtained by condensation at melamine,formaldehyde,dimethylamine molar ratio of 100∶ 330∶ 10. The wet tensile strength of fruit-bagging paper was improved by adding cationized melamine-formaldehyde resin. The zeta potential,charge density,and conductivity of the melamine-formaldehyde resin were also studied.展开更多
A simple and convenient procedure for the synthesis of nitriles by dehydration of aldoxime using supported sulphuric acid on melamine-formaldehyde resin （MFR） under solvent-free condition has been developed. A varie...A simple and convenient procedure for the synthesis of nitriles by dehydration of aldoxime using supported sulphuric acid on melamine-formaldehyde resin （MFR） under solvent-free condition has been developed. A variety of aromatic and aliphatic aldoximes were converted to the corresponding nitriles. The resin was recovered and reused for subsequent reactions. ~ 2011 Ramin Rezaei. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
The nitrogen and oxygen co-doped hollow carbon spheres（HCSs） were prepared via a simple pyrolysis of solid melamine-formaldhyde resin spheres. The carbonization temperature has an important influence on the specific...The nitrogen and oxygen co-doped hollow carbon spheres（HCSs） were prepared via a simple pyrolysis of solid melamine-formaldhyde resin spheres. The carbonization temperature has an important influence on the specific surface area, pore-size distribution and heteroatom contents of HCSs. The synergistic effects of those physical and chemical properties on supercapacitor performance were systematically investigated. Among the HCSs obtained at different temperatures, HCSs-800（co-doped HCSs at 800℃） exhibits the best reversible specific capacitance in 2 mol/L H2SO4 electrolyte and meanwhile maintains a high-class capacitance retention capability. The nitrogen heteroatoms were confirmed to play a crucial role in improving capacitance in an acid medium. This kind of nitrogen doved HCSs is a potential candidate for an efficient electrode material for supercapacitors.展开更多
Melamine-formaldehyde resin supported H~＋ is used as an efficient catalyst in the Pechmann condensation reaction of phenols withβ-ketoesters,in solvent-free media leading to the formation of coumarin derivatives usi...Melamine-formaldehyde resin supported H~＋ is used as an efficient catalyst in the Pechmann condensation reaction of phenols withβ-ketoesters,in solvent-free media leading to the formation of coumarin derivatives using conventional heating and microwave irradiation in excellent yields with good purity.展开更多
Controlling the size of fragranee microcapsules using designed agitator paddles was investigated and studied by CFD simulation. First, different fluid flows were established by varying stirring speeds, reactor scales,...Controlling the size of fragranee microcapsules using designed agitator paddles was investigated and studied by CFD simulation. First, different fluid flows were established by varying stirring speeds, reactor scales, and agitator paddle design, and the effects of each on particle size and distribution of prepared microcapsules were determined. The experimental results showed that the pattern design of orifices in the plate paddles control the flow field well. Narrow particle-size distributio ns of the microcapsules were obtained. The fluid flow characteristics including fluid velocity field, turbulent kinetic energy field, and shear stress distribution for thedifferent agitator paddle types in different reaction kettles were simulated using CFD tech no logy. The correlations between simulated data and experime ntal results were an alyzed. Significantly, the simulated average flow velocity was found to show good negative linear correlation w让h the average particle size of prepared microcapsules, with a correlation of y =-2.166x + 42.626.展开更多
文摘In this work, melamine-formaldehyde resin was cationized by adding modifiers so that the fibers closely bonded to improve their usability and the wet strength of paper was greatly improved. Triethanolamine and dimethylamine were added to modify the melamine-formaldehyde resin,respectively.The mechanism of the cationized resin was explored and the possible chemical reactions were deduced. It was concluded that,with the use of triethanolamine,the most optimum product was obtained by hydroxymethylation for 30 min with a temperature of 85℃ and p H of 9. 0 where n( melamine) ∶ n( formaldehyde) ∶ n( methanol) ∶ n( triethanolamine) was 100 ∶ 330 ∶ 450 ∶ 15. With the combined use of dimethylamine and methanol,the optimal product was acquired by condensation for 30 min at a temperature of 50℃ and p H of 2. 0 at melamine, formaldehyde, methanol, and dimethylamine molar ratio of100∶ 330∶ 350∶ 20. With the only use of dimethylamine,the optimal product was obtained by condensation at melamine,formaldehyde,dimethylamine molar ratio of 100∶ 330∶ 10. The wet tensile strength of fruit-bagging paper was improved by adding cationized melamine-formaldehyde resin. The zeta potential,charge density,and conductivity of the melamine-formaldehyde resin were also studied.
文摘A simple and convenient procedure for the synthesis of nitriles by dehydration of aldoxime using supported sulphuric acid on melamine-formaldehyde resin （MFR） under solvent-free condition has been developed. A variety of aromatic and aliphatic aldoximes were converted to the corresponding nitriles. The resin was recovered and reused for subsequent reactions. ~ 2011 Ramin Rezaei. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
基金Supported by the National Natural Science Foundation of China（Nos.51072048, 51102083）, the Natural Science Foundation of Heilongjiang Province, China（Nos.JC201211, B201107） and the Program for Science and Technology Project of Heilong：jiang Province, China（No.WB 10A204）.
文摘The nitrogen and oxygen co-doped hollow carbon spheres（HCSs） were prepared via a simple pyrolysis of solid melamine-formaldhyde resin spheres. The carbonization temperature has an important influence on the specific surface area, pore-size distribution and heteroatom contents of HCSs. The synergistic effects of those physical and chemical properties on supercapacitor performance were systematically investigated. Among the HCSs obtained at different temperatures, HCSs-800（co-doped HCSs at 800℃） exhibits the best reversible specific capacitance in 2 mol/L H2SO4 electrolyte and meanwhile maintains a high-class capacitance retention capability. The nitrogen heteroatoms were confirmed to play a crucial role in improving capacitance in an acid medium. This kind of nitrogen doved HCSs is a potential candidate for an efficient electrode material for supercapacitors.
文摘Melamine-formaldehyde resin supported H~＋ is used as an efficient catalyst in the Pechmann condensation reaction of phenols withβ-ketoesters,in solvent-free media leading to the formation of coumarin derivatives using conventional heating and microwave irradiation in excellent yields with good purity.
文摘Controlling the size of fragranee microcapsules using designed agitator paddles was investigated and studied by CFD simulation. First, different fluid flows were established by varying stirring speeds, reactor scales, and agitator paddle design, and the effects of each on particle size and distribution of prepared microcapsules were determined. The experimental results showed that the pattern design of orifices in the plate paddles control the flow field well. Narrow particle-size distributio ns of the microcapsules were obtained. The fluid flow characteristics including fluid velocity field, turbulent kinetic energy field, and shear stress distribution for thedifferent agitator paddle types in different reaction kettles were simulated using CFD tech no logy. The correlations between simulated data and experime ntal results were an alyzed. Significantly, the simulated average flow velocity was found to show good negative linear correlation w让h the average particle size of prepared microcapsules, with a correlation of y =-2.166x + 42.626.
