[Objective] The aim was to explore release characteristics of vinyl chlo- ride-vinyl acetate copolymer controlled-release N fertilizer and the effects on minerat nitrogen in soils. [Method] Vinyl chloride-vinyl acetat...[Objective] The aim was to explore release characteristics of vinyl chlo- ride-vinyl acetate copolymer controlled-release N fertilizer and the effects on minerat nitrogen in soils. [Method] Vinyl chloride-vinyl acetate copolymer and hydroxyl-modi- fied VCNAc were taken as coating materials to prepare slow release fertilizer. Nutri- ent release characteristics of VC/VAc slow release fertilizer was evaluated by water immersion method and the effects of VC/VAc slow release fertilizer on mineral ni- trogen were researched by pot experiment. [Result] The release periods of VC-VAc controlled-release urea and hydroxyl-modified VC/VAc coated urea were 60 and 50 d, respectively. Furthermore, the content of ammonium nitrogen reached the peak on the 30th d and the content of nitrate nitrogen reached the peak on the 60th d in soils in treatments with VCNAc and hydroxyl-modified VC/VAc; the content of nitrate nitrogen rose again on the 120th d in the treatment with VC/VAc. In terms of wheat yield, different treatments showed insignificant differences and rice yield in the treatment with VCNAc was significantly higher than that in the treatment with hy- droxyl-modified VCNAc （P〈0.05）. [Conclusion] The release days of slow controlled- release fertilizer vary upon pot experiment method and water immersion method. Slow controlled-release fertilizer is not suitable for monoculture, due to long fertilizer efficiency, but multiple cropping would be optimal for its role to be fully exploited.展开更多
A new zinc acetate catalyst which was prepared from modified activated carbon exhibited extreme activity towards the synthesis of vinyl acetate. The activated carbon was modified by nitric acid, vitriol and peroxyacet...A new zinc acetate catalyst which was prepared from modified activated carbon exhibited extreme activity towards the synthesis of vinyl acetate. The activated carbon was modified by nitric acid, vitriol and peroxyacetic acid （PAA）. The effect on specific area, structure, pH and surface acidity groups of carders by modification was discussed. Amount of carbonyl and carboxyl groups in activated carbon was increased by peroxyacetic acid treatment. The productivity of the new catalyst was 14.58% higher than that of catalyst prepared using untreated activated carbon. The relationship between amount of carbonyl and carboxyl groups （m） and catalyst productivity （P） was P = 1.83 ＋ 2.26 × 10^-3＊e^3.17m. Reaction mechanism was proposed. C 2009 Liang Rong Feng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
Stereolithography(SL)-based three-dimensional(3D) printing technique is an efficient method for the fabrication of alumina ceramics.The alumina slurry is difficult to obtain due to the barrier between hydrophilic alum...Stereolithography(SL)-based three-dimensional(3D) printing technique is an efficient method for the fabrication of alumina ceramics.The alumina slurry is difficult to obtain due to the barrier between hydrophilic alumina and oleophilic resin.It not only requires that the ceramic slurry possessed low viscosity and uniformity,but also requires that the slurry could complete the photocuring process.In this study,vinyl acetate was added in the ceramic slurry as a bridge to connect alumina and resin,and the effects of vinyl acetate content on the microstructure and mechanical properties of the alumina ceramics were systematically investigated.The results showed that the alumina ceramics were composed of three types of particles which included large aggregates,individual particles,and long-columnshaped particles.The shrinkage,bulk density,and crystallite size of the ceramics increased with the increase in vinyl acetate content.The open porosity decreased with the increase in vinyl acetate content.The flexural strength of the ceramics first increased and subsequently decreased with the increase in vinyl acetate content.The shrinkage in Z direction was much greater than that in X or Y direction.Based on the above results,the optimum vinyl acetate content for alumina slurry was 10 wt%,which resulted in sintered ceramic with the shrinkage of 15.6% in X direction,13.5% in Ydirection,21.9% in Z direction,bulk density of 1.9 g·cm^(-3),open porosity of 50.1%,and flexural strength of 24.4 MPa.The sintered ceramics satisfy the requirement of alumina ceramic cores.展开更多
The copolymerization of maleic anhydride and vinyl acetate in tetrahydrofuran was studied. Results show that the maximum copolymerization rate is in 0.6 mole fraction of maleic anhydride, indicating the involvement of...The copolymerization of maleic anhydride and vinyl acetate in tetrahydrofuran was studied. Results show that the maximum copolymerization rate is in 0.6 mole fraction of maleic anhydride, indicating the involvement of maleic anhydride-tetrahydrofuran charge transfer complex in the chain initiation process. ESR study provides collateral evidence for the formation of maleic anhydride radical and tetrahydrofuran radical.展开更多
Graphite oxide, a pseudo-two-dimensional solid in bulk form, was synthesized from natural graphite powder by oxidization with KMnO4 in concentrated H2SO4. The poly(vinyl acetate)-intercalated graphite oxide nano-compo...Graphite oxide, a pseudo-two-dimensional solid in bulk form, was synthesized from natural graphite powder by oxidization with KMnO4 in concentrated H2SO4. The poly(vinyl acetate)-intercalated graphite oxide nano-composite was prepared by an in situ intercalative polymerization reaction, in which n-octanol-graphite oxide intercalation compounds were first obtained, vinyl acetate monomer was then dispersed into the interlayer of modified graphite oxide, followed by thermal polymerization of the monomer. It was experimentally shown that the c-axis space of poly(vinyl acetate)-intercalated graphite oxide was increased to 0.115 nm, which suggested there existed a monolayer of poly(vinyl acetate) chain between the layers of graphite oxide. The nanocomposite was also characterized with thermal analysis and FT-IR spectrometry.展开更多
Because the large areas of Iran are on arid and semiarid belt of the world, it has many problems due to windstorms. Wind storms cause dust and haze due to a mass of fine sand or silt soil elevated in the atmosphere. I...Because the large areas of Iran are on arid and semiarid belt of the world, it has many problems due to windstorms. Wind storms cause dust and haze due to a mass of fine sand or silt soil elevated in the atmosphere. It makes heart disease-cardiovascular and respiratory and so is detrimental for the children. These have plagued the residents and so lives of them are disrupted every so often. In this research, the subject soil stabilization using adherence of poly vinyl acetate polymer as a way to reduce the production of dust is defined for prone area. In this paper, the effect of poly vinyl acetate polymer on silt soil has been studied. In this study the samples were uncompacted particles of soil with different amount of water-solvated polymer (0, 5, 10, 15, 20, 25, 30 grams per meter squared) poured over them. These samples are kept in experimental environment for 7 days. After ensuring complete dryness, their stabilities are tested against wind flow with 20 m/s speed. Results showed that adding more polymers to soil would considerably increase its particles’ stabilities. This stability is due to positive reaction of polymer with soil particles. The effect of this stability is maintained during sample drying time in the lab and the soil maintains its characteristics during testing. The best results are obtained for 20 grams polymer per meter squared, where caused an increase in stability to about 15 times that of the soil without polymer.展开更多
The major difficulty in achieving good performance of industrial polymerization reactors lies in the lack of understanding of their nonlinear dynamics and the lack of well-developed techniques for the control of nonli...The major difficulty in achieving good performance of industrial polymerization reactors lies in the lack of understanding of their nonlinear dynamics and the lack of well-developed techniques for the control of nonlinear processes, which are usually accompanied with bifurcation phenomenon. This work aims at investigating the nonlinear behavior of the parameterized nonlinear system of vinyl acetate polymerization and further modifying the bifurcation characteristics of this process via a washout filter-aid controller, with all the original steady state equilibria preserved. Advantages and possible extensions of the proposed methodology are discussed to provide scientific guide for further controller design and operation improvement.展开更多
Vapor-liquid equilibrium data of hexamethyl disiloxane+vinyl acetate system at 101.3kPa were measured by using double circulating vapor-liquid equilibrium still.The thermodynamic consistency of the VLE data was examin...Vapor-liquid equilibrium data of hexamethyl disiloxane+vinyl acetate system at 101.3kPa were measured by using double circulating vapor-liquid equilibrium still.The thermodynamic consistency of the VLE data was examined by Herrington method.Experimental data was correlated by non-random two-liquid(NRTL),Wilson and universal quasichemical(UNIQUAC)parameter models.All the models satisfactorily correlated with the VLE data.The result showed that the NRTL model was the most suitable one to represent experimental data satisfactorily.The system had a minimum temperature azeotrope at 345.71 K and the mole azeotropic composition was 0.0541.展开更多
The charge-transfer complex of maleic anhydride and vinyl acetate was copolymerized under UV light. The chain composition and structure of the copolymer were analyzed with conductometry and NMR, and the chain sequence...The charge-transfer complex of maleic anhydride and vinyl acetate was copolymerized under UV light. The chain composition and structure of the copolymer were analyzed with conductometry and NMR, and the chain sequence was determined as alternating. The copolymerization rates at different feed ratios, temperatures and in different solvents were investigated, giving evidence to the very active involvement of the CT complexes in the copolymerization. Terpolymerization with acrylonitrile also showed that the complex mechanism was a proper one for this system.展开更多
Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate ...Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate the localization of IFR in the EVA matrix. Localizations in which IFR was dispersed in the PA6phase or in the EVA phase were prepared. The effect of the localization of IFR on the flame retardancy of EVA was investigated. The limited oxygen index (LOI), vertical burning (UL 94) and cone calorimeter test (CCT)showed that the localization of IFR in the EVA matrix exhibited a remarkable influence on the flame retardancy.Compared with EVA/IFR, a weak improvement in the flame retardancy was observed in the EVA/PA6/IFR blend withthe localization of IFR in the PA6 phase. When IFR was regulated from the PA6 phase to the EVA matrix,a remarkable increase in the flame retardancy was exhibited. The LOI was increased from 27.8%to 32.7%, and the UL 94 vertical rating was increased from V-2 to V-0. Moreover, an approximately 41.36%decrease in the peak heat release rate was exhibited. A continuous and compact intumescent charring layer that formed in the blends with the localization of IFR in the EVA matrix should be responsible for its excellent flame retardancy.展开更多
Vinyl acetate radical emulsion polymerization in water with GF51 silane co-monomer was performed by semi continuous way. The GF51 impacts on dispersion rheology as well on films and bonding strength properties were de...Vinyl acetate radical emulsion polymerization in water with GF51 silane co-monomer was performed by semi continuous way. The GF51 impacts on dispersion rheology as well on films and bonding strength properties were determined. It should be stated that even low quantities of GF51 （up to 6% from VAc） determined high viscosity of dispersions. The GF51 modified films have low water absorption and high affinity to glass. Molecular mass and thermal properties of GF51 modified polymers were determined accordingly.展开更多
Three poly(vinyl acetate)(PVAc)oligomers with controlled molecular weight and narrow molecular distribution are synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization.The effects of the re...Three poly(vinyl acetate)(PVAc)oligomers with controlled molecular weight and narrow molecular distribution are synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization.The effects of the reaction temperature and the added amount of initiator of the PVAc polymerization are discussed.In addition,the phase behavior of the prepared PVAc in pressured CO2 is determined via the cloud point method.The results indicate that the cloud point of PVAc increases with the increase in the molecular weight,the PVAc concentration,and the temperature.The cloud point pressures for the PVAc mass concentration of 0.12%with the molecular weight of 1 550,2 120,and 2 960 g/mol are 13.48,13.83 and 15.43 MPa,respectively,at the temperature of 35℃.It reveals that the solubility of PVAc in ScCO2 at relatively low pressure is remarkably limited.展开更多
Compatibility of poly (vinyl acetate) (PVAc) with poly (methyl methacrylate) (PMMA) mixtures has been studied by using nuclear magnetic relaxation, differential scanning calorimeter and small-angle X-ray scattering te...Compatibility of poly (vinyl acetate) (PVAc) with poly (methyl methacrylate) (PMMA) mixtures has been studied by using nuclear magnetic relaxation, differential scanning calorimeter and small-angle X-ray scattering techniques. The nuclear magnetic relaxation time T_1's were measured as a function of composition in blends of PMMA and PVAc prepared from chloroform solution. The results show that the system is miscible for casting from chloroform solution.展开更多
A new process for the co-production of vinyl acetate monomer and acetic acid from ethane feedstock was studied. Various configurations were proposed and simulation results were given for each case to optimize process ...A new process for the co-production of vinyl acetate monomer and acetic acid from ethane feedstock was studied. Various configurations were proposed and simulation results were given for each case to optimize process variables. This new process offers an overall yield values above 70% with minimum separation steps involved and the possibility of utilities integration. The process does not involve any CO production, thus becoming environmentally more favorable. The initial capital investment of the proposed process is much lower compared to the conventional route.展开更多
The discarded feathers / ethylene vinyl acetate copolymer( EVA) thermoplastic composite materials was obtained with discarded feathers as reinforced material and EVA powders as matrix material by hot pressing method. ...The discarded feathers / ethylene vinyl acetate copolymer( EVA) thermoplastic composite materials was obtained with discarded feathers as reinforced material and EVA powders as matrix material by hot pressing method. Sound absorption properties were studied by changing mass ratio of discarded feathers and EVA,thickness of composite materials,hot pressing pressure and hot pressing temperature. It was found that the sound absorption properties of composite materials were good when the mass ratio of discarded feathers and EVA was 1: 1,thickness of composite materials was 30 mm,hot pressing pressure was 8 MPa,and hot pressing temperature was 80 ℃. Under the optimum conditions,the effect of composite density on sound absorption property was analyzed. In a certain range,the sound absorption property was enhanced with the decrease of the composite density.When the composite density was 0. 1g /cm^3, the maximum absorption coefficient was 0.96. Finally,the capillary theory was used to calculate the maximum sound absorption coefficient of discarded feathers / EVA thermoplastic composite materials. The good agreements of experimental results and calculated results proved the validity of the theoretical models.展开更多
Carbon nanotube (CNT) has remarkable piezoresistive properties,which makes its extremely sensitive to the mechanical force. In this study,the CNT yarn with the strength of 90 MPa and the strain sensing gage factor of ...Carbon nanotube (CNT) has remarkable piezoresistive properties,which makes its extremely sensitive to the mechanical force. In this study,the CNT yarn with the strength of 90 MPa and the strain sensing gage factor of 1.75 was selected and embedded into the ethylene vinyl acetate (EVA) elastomer as a sensing material.By measuring the electric resistance changing under the stretching,bending,longitudinally and transversely compressing of the CNT embedded EVA, the resistance changing curves and their linear correlations were obtained and analyzed. The result shows that the gage factor under the tensile test is the highest( 2.51),which is higher than the original value of CNT yarn (1.75). The gage factors of the CNT yarn embedded into EVA elastomer under bending and longitudinal and transverse compression are 2.29,1.55 and 0.79,respectively.展开更多
The blending of natural rubber(NR)with cis-1,4-polybutadiene rubber(BR)has gained widespread attention due to its potential in enhancing the low temperature resistance and abrasion resistance of NR.However,the incompa...The blending of natural rubber(NR)with cis-1,4-polybutadiene rubber(BR)has gained widespread attention due to its potential in enhancing the low temperature resistance and abrasion resistance of NR.However,the incompatibility between NR and BR as well as the non-uniform distribution of fillers often have an adverse impact on the mechanical properties.Herein,we propose a facile approach to modulate the multi-scale structures in NR/BR blends including polymer compatibility and filler distribution by introducing ethylene vinyl acetate(EVA)with varying vinyl acetate(VA)content as multifunctional compatibilizers.The results indicate that the cure characteristics(i.e.,processability)and mechanical properties of NR/BR blends can be readily tailored through adjustment of the VA content in EVA.When the VA content in EVA is increased to 18%(EVA-18),the NR/BR blends simultaneously exhibit favorable processability and mechanical properties.The microstructural analysis demonstrates that the introduction of EVA-18 not only enhances the compatibility between NR and BR with significantly reduced domain size,but also improves fillers dispersion in the rubber matrix.The presence of EVA-18 at concentrations up to 20 parts per hundred of rubber(phr)in NR/BR vulcanizates improves the mechanical properties by approximately 24%compared to un-compatibilized NR/BR vulcanizates,which is superior to the most present studies.This work will be beneficial for the development of NR/BR blends in the industry and provide a guideline for designing efficient compatibilizers for other immiscible rubber blends.展开更多
The main problem in an efficient Zn（CH3COO）2/AC （AC-activated carbon） catalyst preparation is the achievement of uniform distribution of highly dispersed salt component on the activated carbon （AC） surface. The ...The main problem in an efficient Zn（CH3COO）2/AC （AC-activated carbon） catalyst preparation is the achievement of uniform distribution of highly dispersed salt component on the activated carbon （AC） surface. The solution of this problem is modification of the AC by hydrogen peroxide （H202） oxidation of the surface and treatment of AC with acetic acid as well as special methods of salt deposition and catalyst drying. The investigations of these ways of AC surface modification （treatment of AC with acetic acid and H2O2） have demonstrated the obtained AC to have both an increased adsorption capacity as to Zn（OAc）2 and optimum volumes of meso- and micro-pores as well as high catalyst activity in vinyl acetate （VA） synthesis. The characteristics of supports and catalysts were found out by benzene, water and acetic acid vapors adsorption. The distribution of the salt on the AC surface was studied by small-angle X-ray scattering （SAXS）, by scanning electron microscopy （SEM） and X-ray micro-analysis （XMA）. The catalysts were tested in vinyl acetate synthesis in flow-bed isothermal reactor by cyclic method at 175, 205 and 230℃.展开更多
The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerizat...The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerization two steps were explored. First, 5 grams CAGB with 2.5 mm initial diameter was initiated with 0.0493 mol/L K2S2O8 at 51 °C for 30 min in 15 mL 1 % PVA/H2O. Then 4.34 moi/L VAc was added dropwise and the reaction was allowed to proce at 48 °C for 3 h. The grafting efficiency could come up to 30%. It was found the stability of modified CAGB in the air and in electrolyte solutions was greatly improved.展开更多
The effects of magnesium oxide （MgO） on the flame retardant performance of intumescent systems based on ammonium polyphosphate （APP） and pentaerythritol （PER） in ethylene vinyl acetate copolymer （EVA） were stu...The effects of magnesium oxide （MgO） on the flame retardant performance of intumescent systems based on ammonium polyphosphate （APP） and pentaerythritol （PER） in ethylene vinyl acetate copolymer （EVA） were studied. The results showed that MgO affects both the quality and quantity of residual char. There is an optimal value for the loading amount of MgO. More or less MgO loading may cause the formation of defective char layers and worsen the flame retardancy of EVA. According to the results of limiting oxygen index （LOI）, vertical flammability test （UL94 rating） and cone calorimetry （CONE）, the best flame retardancy with a strong and well intumescent char is obtained from the sample with 1 wt% of MgO, which has the highest LOI value of 27.9, UL94 rating of V-0 and the lowest peak heat release rate of 242 kW·m-2.展开更多
基金Supported by National Department Public Benefit Research Foundation(201203013)Modern Agricultural Industry Technology System(CARS-11-B-15)+2 种基金IPNI Project(JIANGSU-10)Special Fund for Agro-scientific Research in the Public Interest(201003014-1-2)Jiangsu Agriculture S&T Self-Innovation Project[CX(12)3037]~~
文摘[Objective] The aim was to explore release characteristics of vinyl chlo- ride-vinyl acetate copolymer controlled-release N fertilizer and the effects on minerat nitrogen in soils. [Method] Vinyl chloride-vinyl acetate copolymer and hydroxyl-modi- fied VCNAc were taken as coating materials to prepare slow release fertilizer. Nutri- ent release characteristics of VC/VAc slow release fertilizer was evaluated by water immersion method and the effects of VC/VAc slow release fertilizer on mineral ni- trogen were researched by pot experiment. [Result] The release periods of VC-VAc controlled-release urea and hydroxyl-modified VC/VAc coated urea were 60 and 50 d, respectively. Furthermore, the content of ammonium nitrogen reached the peak on the 30th d and the content of nitrate nitrogen reached the peak on the 60th d in soils in treatments with VCNAc and hydroxyl-modified VC/VAc; the content of nitrate nitrogen rose again on the 120th d in the treatment with VC/VAc. In terms of wheat yield, different treatments showed insignificant differences and rice yield in the treatment with VCNAc was significantly higher than that in the treatment with hy- droxyl-modified VCNAc （P〈0.05）. [Conclusion] The release days of slow controlled- release fertilizer vary upon pot experiment method and water immersion method. Slow controlled-release fertilizer is not suitable for monoculture, due to long fertilizer efficiency, but multiple cropping would be optimal for its role to be fully exploited.
文摘A new zinc acetate catalyst which was prepared from modified activated carbon exhibited extreme activity towards the synthesis of vinyl acetate. The activated carbon was modified by nitric acid, vitriol and peroxyacetic acid （PAA）. The effect on specific area, structure, pH and surface acidity groups of carders by modification was discussed. Amount of carbonyl and carboxyl groups in activated carbon was increased by peroxyacetic acid treatment. The productivity of the new catalyst was 14.58% higher than that of catalyst prepared using untreated activated carbon. The relationship between amount of carbonyl and carboxyl groups （m） and catalyst productivity （P） was P = 1.83 ＋ 2.26 × 10^-3＊e^3.17m. Reaction mechanism was proposed. C 2009 Liang Rong Feng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
基金financially supported by the National Key Research and Development Program of China(No.2018YFB1106600)the National Natural Foundation of China(No.51672217)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(No.CX202006)。
文摘Stereolithography(SL)-based three-dimensional(3D) printing technique is an efficient method for the fabrication of alumina ceramics.The alumina slurry is difficult to obtain due to the barrier between hydrophilic alumina and oleophilic resin.It not only requires that the ceramic slurry possessed low viscosity and uniformity,but also requires that the slurry could complete the photocuring process.In this study,vinyl acetate was added in the ceramic slurry as a bridge to connect alumina and resin,and the effects of vinyl acetate content on the microstructure and mechanical properties of the alumina ceramics were systematically investigated.The results showed that the alumina ceramics were composed of three types of particles which included large aggregates,individual particles,and long-columnshaped particles.The shrinkage,bulk density,and crystallite size of the ceramics increased with the increase in vinyl acetate content.The open porosity decreased with the increase in vinyl acetate content.The flexural strength of the ceramics first increased and subsequently decreased with the increase in vinyl acetate content.The shrinkage in Z direction was much greater than that in X or Y direction.Based on the above results,the optimum vinyl acetate content for alumina slurry was 10 wt%,which resulted in sintered ceramic with the shrinkage of 15.6% in X direction,13.5% in Ydirection,21.9% in Z direction,bulk density of 1.9 g·cm^(-3),open porosity of 50.1%,and flexural strength of 24.4 MPa.The sintered ceramics satisfy the requirement of alumina ceramic cores.
基金Projects supported by the National Natural Science Foundation of China
文摘The copolymerization of maleic anhydride and vinyl acetate in tetrahydrofuran was studied. Results show that the maximum copolymerization rate is in 0.6 mole fraction of maleic anhydride, indicating the involvement of maleic anhydride-tetrahydrofuran charge transfer complex in the chain initiation process. ESR study provides collateral evidence for the formation of maleic anhydride radical and tetrahydrofuran radical.
基金Financial support from Key Project of The National Natural Science Foundation of China (No. 59836230) is gratefully acknowledged.
文摘Graphite oxide, a pseudo-two-dimensional solid in bulk form, was synthesized from natural graphite powder by oxidization with KMnO4 in concentrated H2SO4. The poly(vinyl acetate)-intercalated graphite oxide nano-composite was prepared by an in situ intercalative polymerization reaction, in which n-octanol-graphite oxide intercalation compounds were first obtained, vinyl acetate monomer was then dispersed into the interlayer of modified graphite oxide, followed by thermal polymerization of the monomer. It was experimentally shown that the c-axis space of poly(vinyl acetate)-intercalated graphite oxide was increased to 0.115 nm, which suggested there existed a monolayer of poly(vinyl acetate) chain between the layers of graphite oxide. The nanocomposite was also characterized with thermal analysis and FT-IR spectrometry.
文摘Because the large areas of Iran are on arid and semiarid belt of the world, it has many problems due to windstorms. Wind storms cause dust and haze due to a mass of fine sand or silt soil elevated in the atmosphere. It makes heart disease-cardiovascular and respiratory and so is detrimental for the children. These have plagued the residents and so lives of them are disrupted every so often. In this research, the subject soil stabilization using adherence of poly vinyl acetate polymer as a way to reduce the production of dust is defined for prone area. In this paper, the effect of poly vinyl acetate polymer on silt soil has been studied. In this study the samples were uncompacted particles of soil with different amount of water-solvated polymer (0, 5, 10, 15, 20, 25, 30 grams per meter squared) poured over them. These samples are kept in experimental environment for 7 days. After ensuring complete dryness, their stabilities are tested against wind flow with 20 m/s speed. Results showed that adding more polymers to soil would considerably increase its particles’ stabilities. This stability is due to positive reaction of polymer with soil particles. The effect of this stability is maintained during sample drying time in the lab and the soil maintains its characteristics during testing. The best results are obtained for 20 grams polymer per meter squared, where caused an increase in stability to about 15 times that of the soil without polymer.
基金Supported by the National Basic Research Programme(2012CB720500)the National Natural Science Foundation of China(21306100)
文摘The major difficulty in achieving good performance of industrial polymerization reactors lies in the lack of understanding of their nonlinear dynamics and the lack of well-developed techniques for the control of nonlinear processes, which are usually accompanied with bifurcation phenomenon. This work aims at investigating the nonlinear behavior of the parameterized nonlinear system of vinyl acetate polymerization and further modifying the bifurcation characteristics of this process via a washout filter-aid controller, with all the original steady state equilibria preserved. Advantages and possible extensions of the proposed methodology are discussed to provide scientific guide for further controller design and operation improvement.
文摘Vapor-liquid equilibrium data of hexamethyl disiloxane+vinyl acetate system at 101.3kPa were measured by using double circulating vapor-liquid equilibrium still.The thermodynamic consistency of the VLE data was examined by Herrington method.Experimental data was correlated by non-random two-liquid(NRTL),Wilson and universal quasichemical(UNIQUAC)parameter models.All the models satisfactorily correlated with the VLE data.The result showed that the NRTL model was the most suitable one to represent experimental data satisfactorily.The system had a minimum temperature azeotrope at 345.71 K and the mole azeotropic composition was 0.0541.
基金Projects supported by the Science Fund of the Chinese Academy of Sciences
文摘The charge-transfer complex of maleic anhydride and vinyl acetate was copolymerized under UV light. The chain composition and structure of the copolymer were analyzed with conductometry and NMR, and the chain sequence was determined as alternating. The copolymerization rates at different feed ratios, temperatures and in different solvents were investigated, giving evidence to the very active involvement of the CT complexes in the copolymerization. Terpolymerization with acrylonitrile also showed that the complex mechanism was a proper one for this system.
基金the National Natural Science Foundation of China (No.51673059)the Science and Technology Planning Project of Henan Province (No. 212102210636)the Opening Project of Jiangxi Province Key Laboratory of Polymer Micro/Nano Manufacturing and Devices (East China University of Technology)。
文摘Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate the localization of IFR in the EVA matrix. Localizations in which IFR was dispersed in the PA6phase or in the EVA phase were prepared. The effect of the localization of IFR on the flame retardancy of EVA was investigated. The limited oxygen index (LOI), vertical burning (UL 94) and cone calorimeter test (CCT)showed that the localization of IFR in the EVA matrix exhibited a remarkable influence on the flame retardancy.Compared with EVA/IFR, a weak improvement in the flame retardancy was observed in the EVA/PA6/IFR blend withthe localization of IFR in the PA6 phase. When IFR was regulated from the PA6 phase to the EVA matrix,a remarkable increase in the flame retardancy was exhibited. The LOI was increased from 27.8%to 32.7%, and the UL 94 vertical rating was increased from V-2 to V-0. Moreover, an approximately 41.36%decrease in the peak heat release rate was exhibited. A continuous and compact intumescent charring layer that formed in the blends with the localization of IFR in the EVA matrix should be responsible for its excellent flame retardancy.
文摘Vinyl acetate radical emulsion polymerization in water with GF51 silane co-monomer was performed by semi continuous way. The GF51 impacts on dispersion rheology as well on films and bonding strength properties were determined. It should be stated that even low quantities of GF51 （up to 6% from VAc） determined high viscosity of dispersions. The GF51 modified films have low water absorption and high affinity to glass. Molecular mass and thermal properties of GF51 modified polymers were determined accordingly.
基金The Natural Science Foundation of Jiangsu Province(No.BK20130602)the Applied Basic Research Program of Suzhou(No.SYG201836)the Project of the Collaborative Innovation Center of Suzhou Nano Science and Technology
文摘Three poly(vinyl acetate)(PVAc)oligomers with controlled molecular weight and narrow molecular distribution are synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization.The effects of the reaction temperature and the added amount of initiator of the PVAc polymerization are discussed.In addition,the phase behavior of the prepared PVAc in pressured CO2 is determined via the cloud point method.The results indicate that the cloud point of PVAc increases with the increase in the molecular weight,the PVAc concentration,and the temperature.The cloud point pressures for the PVAc mass concentration of 0.12%with the molecular weight of 1 550,2 120,and 2 960 g/mol are 13.48,13.83 and 15.43 MPa,respectively,at the temperature of 35℃.It reveals that the solubility of PVAc in ScCO2 at relatively low pressure is remarkably limited.
文摘Compatibility of poly (vinyl acetate) (PVAc) with poly (methyl methacrylate) (PMMA) mixtures has been studied by using nuclear magnetic relaxation, differential scanning calorimeter and small-angle X-ray scattering techniques. The nuclear magnetic relaxation time T_1's were measured as a function of composition in blends of PMMA and PVAc prepared from chloroform solution. The results show that the system is miscible for casting from chloroform solution.
文摘A new process for the co-production of vinyl acetate monomer and acetic acid from ethane feedstock was studied. Various configurations were proposed and simulation results were given for each case to optimize process variables. This new process offers an overall yield values above 70% with minimum separation steps involved and the possibility of utilities integration. The process does not involve any CO production, thus becoming environmentally more favorable. The initial capital investment of the proposed process is much lower compared to the conventional route.
文摘The discarded feathers / ethylene vinyl acetate copolymer( EVA) thermoplastic composite materials was obtained with discarded feathers as reinforced material and EVA powders as matrix material by hot pressing method. Sound absorption properties were studied by changing mass ratio of discarded feathers and EVA,thickness of composite materials,hot pressing pressure and hot pressing temperature. It was found that the sound absorption properties of composite materials were good when the mass ratio of discarded feathers and EVA was 1: 1,thickness of composite materials was 30 mm,hot pressing pressure was 8 MPa,and hot pressing temperature was 80 ℃. Under the optimum conditions,the effect of composite density on sound absorption property was analyzed. In a certain range,the sound absorption property was enhanced with the decrease of the composite density.When the composite density was 0. 1g /cm^3, the maximum absorption coefficient was 0.96. Finally,the capillary theory was used to calculate the maximum sound absorption coefficient of discarded feathers / EVA thermoplastic composite materials. The good agreements of experimental results and calculated results proved the validity of the theoretical models.
基金National Natural Science Foundations of China(Nos.51303025,51503120)Shanghai Science and Technology Committee,China(No.14YF1409600)+2 种基金Shanghai Municipal Education Commission,China(No.ZZgcd14016)Fundamental Research Funds for the Central Universities,ChinaDonghua University Distinguished Young Professor Program,China
文摘Carbon nanotube (CNT) has remarkable piezoresistive properties,which makes its extremely sensitive to the mechanical force. In this study,the CNT yarn with the strength of 90 MPa and the strain sensing gage factor of 1.75 was selected and embedded into the ethylene vinyl acetate (EVA) elastomer as a sensing material.By measuring the electric resistance changing under the stretching,bending,longitudinally and transversely compressing of the CNT embedded EVA, the resistance changing curves and their linear correlations were obtained and analyzed. The result shows that the gage factor under the tensile test is the highest( 2.51),which is higher than the original value of CNT yarn (1.75). The gage factors of the CNT yarn embedded into EVA elastomer under bending and longitudinal and transverse compression are 2.29,1.55 and 0.79,respectively.
基金support of National Natural Science Foundation of China(22108182,22278277)the Research Matching Grant Scheme of CUHK(8601309)the Fundamental Research Funds for the Central Universities(2023SCU12105)are gratefully acknowledged.
文摘The blending of natural rubber(NR)with cis-1,4-polybutadiene rubber(BR)has gained widespread attention due to its potential in enhancing the low temperature resistance and abrasion resistance of NR.However,the incompatibility between NR and BR as well as the non-uniform distribution of fillers often have an adverse impact on the mechanical properties.Herein,we propose a facile approach to modulate the multi-scale structures in NR/BR blends including polymer compatibility and filler distribution by introducing ethylene vinyl acetate(EVA)with varying vinyl acetate(VA)content as multifunctional compatibilizers.The results indicate that the cure characteristics(i.e.,processability)and mechanical properties of NR/BR blends can be readily tailored through adjustment of the VA content in EVA.When the VA content in EVA is increased to 18%(EVA-18),the NR/BR blends simultaneously exhibit favorable processability and mechanical properties.The microstructural analysis demonstrates that the introduction of EVA-18 not only enhances the compatibility between NR and BR with significantly reduced domain size,but also improves fillers dispersion in the rubber matrix.The presence of EVA-18 at concentrations up to 20 parts per hundred of rubber(phr)in NR/BR vulcanizates improves the mechanical properties by approximately 24%compared to un-compatibilized NR/BR vulcanizates,which is superior to the most present studies.This work will be beneficial for the development of NR/BR blends in the industry and provide a guideline for designing efficient compatibilizers for other immiscible rubber blends.
文摘The main problem in an efficient Zn（CH3COO）2/AC （AC-activated carbon） catalyst preparation is the achievement of uniform distribution of highly dispersed salt component on the activated carbon （AC） surface. The solution of this problem is modification of the AC by hydrogen peroxide （H202） oxidation of the surface and treatment of AC with acetic acid as well as special methods of salt deposition and catalyst drying. The investigations of these ways of AC surface modification （treatment of AC with acetic acid and H2O2） have demonstrated the obtained AC to have both an increased adsorption capacity as to Zn（OAc）2 and optimum volumes of meso- and micro-pores as well as high catalyst activity in vinyl acetate （VA） synthesis. The characteristics of supports and catalysts were found out by benzene, water and acetic acid vapors adsorption. The distribution of the salt on the AC surface was studied by small-angle X-ray scattering （SAXS）, by scanning electron microscopy （SEM） and X-ray micro-analysis （XMA）. The catalysts were tested in vinyl acetate synthesis in flow-bed isothermal reactor by cyclic method at 175, 205 and 230℃.
基金This work was supported by the Young Scientist & Technician Creation Item sponsored by Fujian Province (No. 2002J021)and Scientific Research Fund Sponsored by Huaqiao University.
文摘The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerization two steps were explored. First, 5 grams CAGB with 2.5 mm initial diameter was initiated with 0.0493 mol/L K2S2O8 at 51 °C for 30 min in 15 mL 1 % PVA/H2O. Then 4.34 moi/L VAc was added dropwise and the reaction was allowed to proce at 48 °C for 3 h. The grafting efficiency could come up to 30%. It was found the stability of modified CAGB in the air and in electrolyte solutions was greatly improved.
基金financially supported by the National Natural Science Foundation of China(No.51203136)the Scientific Special Fund of Zhejiang Province(No.2013C01074)
文摘The effects of magnesium oxide （MgO） on the flame retardant performance of intumescent systems based on ammonium polyphosphate （APP） and pentaerythritol （PER） in ethylene vinyl acetate copolymer （EVA） were studied. The results showed that MgO affects both the quality and quantity of residual char. There is an optimal value for the loading amount of MgO. More or less MgO loading may cause the formation of defective char layers and worsen the flame retardancy of EVA. According to the results of limiting oxygen index （LOI）, vertical flammability test （UL94 rating） and cone calorimetry （CONE）, the best flame retardancy with a strong and well intumescent char is obtained from the sample with 1 wt% of MgO, which has the highest LOI value of 27.9, UL94 rating of V-0 and the lowest peak heat release rate of 242 kW·m-2.
