The Rouse-Zimm model with slippage was improved and the basic parameters of modelwere modified to explain the rheological properties of star-type branched polymersolutions. The theoretical results show good agreement ...The Rouse-Zimm model with slippage was improved and the basic parameters of modelwere modified to explain the rheological properties of star-type branched polymersolutions. The theoretical results show good agreement with experimental data.展开更多
The polymer solution flow in porous media is a central research topic related to hydraulic fracturing measures,formation damage and fracture propagation.Influenced by molecular weights and concentrations,various flow ...The polymer solution flow in porous media is a central research topic related to hydraulic fracturing measures,formation damage and fracture propagation.Influenced by molecular weights and concentrations,various flow patterns of polymer in pores are presented,resulting in different filtration loss.In this work,the effectiveness of various polymer solutions for filtration loss was assessed by utilizing the core flooding experiment firstly.The result shows that lesser filtration loss normally is inextricably linked to solutions with high molecular weight and concentration.Subsequently,the flow behaviors of polymer solutions investigated by designed micro pore-throat structure and micro-particle image velocimetry(m-PIV)further confirmed the above result.It was found that the central convergent flow pattern benefiting from higher viscous force loss and less filtration loss was observed at high flow rates(0.5 mL/h),and higher molecular weight and concentration were more prone to convergent flow patterns.The viscosity force loss increases by about 4 times varying the molecular weight of polymer from 5×10^(6)to 18×10^(6)g/mol or the concentration from 0.05 to 0.3%.It interprets higher molecular weight and concentration in core studies and field observations with decreased filtration loss of HPAM.This work provides a theoretical foundation for the application of fracturing fluids as well as fresh perspectives on how to access the filtration loss of fracturing fluids.展开更多
Entanglement network is an important structural feature in concentrated polymer solutions and polymer melts,which has a great influe nee on the transie nt rheological behavior and molecular con figurati on evolution.H...Entanglement network is an important structural feature in concentrated polymer solutions and polymer melts,which has a great influe nee on the transie nt rheological behavior and molecular con figurati on evolution.However,the existi ng constitutive models have limitations in describi ng the influe nee of dyn amic entan glement behavior on molecular chain motion,resulti ng in inaccurate descriptions of the transient rheological behavior.Thus,a molecular con figuration evoluti on model for polymer solutions considering the dyn amic entanglement effect is proposed by introducing an intermolecular force that changes with the orientation of the molecular chain in this work.The intermolecular force is introduced by consider!ng the friction coefficient as anisotropic,and the orientation effect is considered by introducing an excluded volume depende nt an isotropic diffusi on.The proposed model can better describe the stress relaxation,stress growth,and dielectric an isotropy of polymer soluti ons compared with the an isotropy FENE model and FENE model.In addition,the in fluence of different model parameters on the transient and steady shear response of polymer soluti on is investigated,and the results show that the in fluence of volume loss on the fricti on anisotropy factor k0 in creases as the solution concen tration in creases.展开更多
Based on the molecular theory of non-linear viscoelasticity with constrained entanglements in polymer melts, the material functions in simple shear flow were formulated, the theoretical relations between and shear rat...Based on the molecular theory of non-linear viscoelasticity with constrained entanglements in polymer melts, the material functions in simple shear flow were formulated, the theoretical relations between and shear rate (), and topologically constrained dimension number and a were derived. Linear viscoelastic parameters and and topologically constrained dimension number and as a function of the primary molecular weight, molecular weight between entanglements and the entanglement sites sequence distribution in polymer chain were determined. A new method for determination of viscoelastic parameters G and topologically constrained dimension number a and and molecular weight and from the shear flow measurements was proposed. It was used to determine those parameters and structures of HDPE, making a good agreement between these values and those obtained by other methods. The agreement affords a quantitative verification for the molecular theory of nonlinear viscoelasticity with constrained entanglement in polymer melts.展开更多
It is shown theoretically that the viscoelasticity of polymer melts is determined by three combining factorst they are the primary molecular weight and its distribution, the number of entanglement sites on polymer cha...It is shown theoretically that the viscoelasticity of polymer melts is determined by three combining factorst they are the primary molecular weight and its distribution, the number of entanglement sites on polymer chain and the sequence distribution of constituent chains in entanglement spacings. A unified quantity for the three combing factors is the average constrained dimensional number of constituent chains in the long entanglement spacings (v). A new relation of v to the primary molecular weight and the number of testing polymers were derived from the multiple entanglement and reptation model, and a new method for determining v was proposed. The dependences of linear viscoelastic functions on the primary molecular weight and its distribution were derived by the statistical method. When Mn=6Me to 18 Me, the values of (v) can range from 3.33 to 3.70. Their values are in a good agreement with the experiment data, and it can slightjy vary with the different species of polymers and the different ranges of molecular weight of polymers展开更多
An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model stru...An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results展开更多
Critical association concentration (Ca) of ethylene-vinyl acetate copolymer (EVA) in selective solvent mixtures of 1,2-dichloroethane (DCE) (polar solvent) and cyclohexane (CYH) (non-polar solvent) was investigated. D...Critical association concentration (Ca) of ethylene-vinyl acetate copolymer (EVA) in selective solvent mixtures of 1,2-dichloroethane (DCE) (polar solvent) and cyclohexane (CYH) (non-polar solvent) was investigated. DCE is a good solvent for polyvinyl acetate (PVAc) and a poor solvent for paraffin, whereas CYH is a good solvent for the paraffin and a precipitant for PVAc. Viscosities of EVA in different compositions of the solvent mixture with and without additives were measured. Viscosity results were used to determine the C-A value of the systems. It is shown that C-A was markedly dependent on the composition of the solvent mixture and concentration and structure of the additive. Solvation and competition between hydrogen bonding and micellisation were suggested for qualitative description of the changing of C-A value observed.展开更多
Performance characteristics of partially hydrolyzed polyacrylamide (HPAM) and cross- linked polymer (CLP, Cr^3+ as the cross linker) solutions have been investigated. A Brookfield viscometer, rheometer, dynamic l...Performance characteristics of partially hydrolyzed polyacrylamide (HPAM) and cross- linked polymer (CLP, Cr^3+ as the cross linker) solutions have been investigated. A Brookfield viscometer, rheometer, dynamic light scattering system, and core flow device have been used to measure the viscosity, viscoelasticity, polymer coil dimensions, molecular configuration, flow characteristics, and profile modification. The results show that, under conditions of high salinity and low HPAM and Cr^3+ concentrations, cross-linking mainly occurred between different chains of the same HPAM molecule in the presence of Cr^3+, and a cross-linked polymer (CLP) system with a local network structure was formed. Compared with an HPAM solution of the same concentration, the apparent viscosity of the CLP solution increased slightly or remained almost unchanged, but its viscoelasticity (namely storage modulus, loss modulus, and first normal stress difference) increased, and the resistance coefficient and residual resistance coefficient increased significantly. This indicates that the CLP solution exhibits a strong capability to divert the sequentially injected polymer flood from high-permeability zones to low- permeability zones in a reservoir. Under the same HPAM concentration conditions, the dimensions of polymer coils in the CLP solution increased slightly compared with the dimensions of polymer coils in HPAM solution, which were smaller than the rock pores, indicating that the cross-linked polymer solution was well adapted to reservoir rocks. Core flood experiments show that at the same cost of reagent, the oil recovery by CLP injection (HPAM-1, Cr^3+ as the cross linker) is 3.1% to 5.2% higher than that by HPAM- 2 injection.展开更多
The concentration dependence of the reduced viscosity of dilute polymer solution is interpreted in the light of a new concept of the self-association of polymer chains in dilute solution. The apparent self-association...The concentration dependence of the reduced viscosity of dilute polymer solution is interpreted in the light of a new concept of the self-association of polymer chains in dilute solution. The apparent self-association constant is defined as the molar association constant divided by the molar mass of individual polymer chain and is numerically interconvertible with the Huggins coefficient. The molar association constant is directly proportional to the effective hydrodynamic volume of the polymer chain in solution and is irrespective of the chain architecture. The effective hydrodynamic volume accounts for the non-spherical conformation of a short polymer chain in solution and is a product of a shape factor and hydrodynamic volume. The observed enhancement of Huggins coefficient for short chain and branched polymer is satisfactorily interpreted by the concept of self-association. The concept of self-association allows us to predict the existence of a boundary concentration C-s(dynamic contact concentration) which divides the dilute polymer solution into two regions.展开更多
The influence of dissolved oxygen content on the oxidative stability of a linked polymer solution (LPS) was studied by micro-filtration, dynamic light scattering and viscosity measurements. The results showed that at ...The influence of dissolved oxygen content on the oxidative stability of a linked polymer solution (LPS) was studied by micro-filtration, dynamic light scattering and viscosity measurements. The results showed that at the same temperature, the degree of the oxidative degradation of the LPS increased and the rapidity of the oxidative degradation was accelerated with the increase of the dissolved oxygen content. Consequently, the size of linked polymer coils (LPCs) of the LPS became small, and the plugging capability of the LPS decreased. At a fixed content of dissolved oxygen, with increasing degradation temperature, almost the same results were observed, namely, an increased degree of oxidative degradation, accelerated rapidity of the oxidative degradation and decreased plugging capacity, with decreased oxidative stability of LPS. At 90 °C, in the presence of oxygen, LPS lost its plugging capability after having been degraded for a period of time. But at 40 °C, LPS with low dissolved oxygen content could be stable for a long time. The decreased plugging ability of LPS after oxidative degradation is mainly caused by the decreased size and number of the LPCs due to the breaking of hydrolyzed polyacrylamide (HPAM) molecule segments and the structural changing of HPAM molecules.展开更多
Careful measurements of the dilute solution viscosities of polyethylene glycol and polyvinyl alcohol in water were carried out. The reduced viscosities of both polymer solutions plot upward curves at extremely dilute ...Careful measurements of the dilute solution viscosities of polyethylene glycol and polyvinyl alcohol in water were carried out. The reduced viscosities of both polymer solutions plot upward curves at extremely dilute concentration levels similar to the phenomena observed for many polymer solutions in the early 1950's. Upon observation of the changes of the flow times of pure water in and the wall surface wettability of the viscometer after measuring solution viscosity, a view was formed that the observed viscosity abnormality at extremely dilute concentration regions is solely due to the effect of adsorption of polymer chains onto the wall surface of viscometer. A theory of adsorption effect based on the Langmuir isotherms was proposed and a mathematical; analysis for data treatment was performed. The theory could adequately describe the existing viscosity data. It seems necessary to correct the viscosity result of dilute polymer solutions measured by glass capillary viscometer by taking into account the effect of adsorption in all cases.展开更多
The diffusion coefficients(Dapp) and the heterogeneous electron transfer rate constants(ks)for ferrocene in several polymer solvents were determined by using steady-stae voltammetry. Thetemperature dependence of the t...The diffusion coefficients(Dapp) and the heterogeneous electron transfer rate constants(ks)for ferrocene in several polymer solvents were determined by using steady-stae voltammetry. Thetemperature dependence of the two parameters indicates Arrhenius behavior. The polymer solventeffects on diffusion and electron transfer dynamics of ferrocene were discussed展开更多
The statistical counting method for the computer simulation of the thermodynamic quantities of polymer solution has been reviewed. The calculating results for a single athermal chain confirm the theory of the renorma...The statistical counting method for the computer simulation of the thermodynamic quantities of polymer solution has been reviewed. The calculating results for a single athermal chain confirm the theory of the renormalization group. The results for the athermal solution are consistent with the scaling law of the osmotic pressure with the exponent 2.25. The results for a single chain with the segmental interaction are in a good agreement with the exact results obtained by the direct counting method. The results for the polymer solution show us that the Flory-Huggins parameter is strongly dependent on both the polymer concentration and the interaction energy between segments. (Author abstract) 15 Refs.展开更多
The calculations presented in this paper are based on the Sanchez-Lacombe(SL)lattice fluid theory.The interaction energy parameter,g12/k,required in this approach was obtained by fitting the cloud points of polystyr...The calculations presented in this paper are based on the Sanchez-Lacombe(SL)lattice fluid theory.The interaction energy parameter,g12/k,required in this approach was obtained by fitting the cloud points of polystyrene(PS)/methylcyclohexane(MCH)polymer solutions under pressure.The SL lattice fluid theory was used to calculate the spinodals,the binodals,and the Flory-Huggins(FH)interaction parameter of the solutions.The calculated results show that the SL lattice fluid theory can describe the dependences of thermodynamics of PS/MCH solutions on temperature and pressure very well.However,the calculated enthalpy and the excess volume changes indicate that the Clausius-Clapeyron equation cannot be suitable to describe pressure effect on PS/MCH solutions.Further analysis on the thermodynamics of this system under pressure shows that the role of entropy is more important than the excess volume in the present case.展开更多
The microscopic oil displacement mechanism in viscoelastic polymer flooding is theoretically analyzed with mechanical method.The effects of viscoelasticity of polymer solution on such three kinds of residual oil as in...The microscopic oil displacement mechanism in viscoelastic polymer flooding is theoretically analyzed with mechanical method.The effects of viscoelasticity of polymer solution on such three kinds of residual oil as in pore throat,in sudden expansion pore path,and in dead end are analyzed.Results show that the critical radius of mobile residual oil for viscoelastic polymer solution is larger than that for viscous polymer solution,which makes the oil that is immobile in viscous polymer flooding displaced under the condition of viscoelastic polymer solution.The viscous polymer solution hardly displaces the oil in dead ends.However,when the effect of viscoelasticity is considered,the residual oil in sudden expansion pore paths and dead ends can be partly displaced. A dimensionless parameter is suggested to denote the relative dominance of gravity and capillary pressure.The larger the dimensionless parameter,the more accurate the increment expressions.展开更多
Low molecular weight poly(glycidyl methacrylate)s (PGMAs) were prepared by photopolymerization in ethyl acetate, with benzophenone (BP) as photoinitiator, and triethylamine (TEA) as hydrogen donor. The existen...Low molecular weight poly(glycidyl methacrylate)s (PGMAs) were prepared by photopolymerization in ethyl acetate, with benzophenone (BP) as photoinitiator, and triethylamine (TEA) as hydrogen donor. The existence of semipinacol dormant end groups in PGMA was confirmed by FT-IR and ^1H-NMR, and the content of the semipinacol dormant groups was determined quantitatively by ^1H-NMR measurement. The effects of various thctors, such as reaction time, BP concentration and monomer concentration on the synthesis of the polymers were investigated systematically. The molecular weights of the polymers were also investigated with GPC. It is shown that increasing BP concentration and decreasing irradiation time and monomer concentration led to a significant decrease of the molecular weights.展开更多
This paper mainly deals with the design and synthesis of a novel styrene-butadieneblock copolymer. When this copolymer is used in the tread portion of tyres, it can improvewet skid resistance and reduce rolling resist...This paper mainly deals with the design and synthesis of a novel styrene-butadieneblock copolymer. When this copolymer is used in the tread portion of tyres, it can improvewet skid resistance and reduce rolling resistance without sacrificing its general physical-mechanical properties. The visco-elastic curve of tire tread using the novel copolymer asits rubber portion was showed. Reactivity ratios for two monomers in the polymerizingsystem were calculated. The diagrams of differelitial, integral and finite difference calculithroughout the whole molecular chain were presented. The influence of the micro- andmacro-structure of the copolymer chain on wet skid resistance and rolling resistance wasdiscussed展开更多
The diffusion coefficients(Dapp) and the heterogeneous electron-transfer rate constants(ks)for ferrocene and its seven derivatives in MPEG/LiClO4 electrolyte were determined by using steadystate voltammetry. The two p...The diffusion coefficients(Dapp) and the heterogeneous electron-transfer rate constants(ks)for ferrocene and its seven derivatives in MPEG/LiClO4 electrolyte were determined by using steadystate voltammetry. The two parameters increase with increasing temperature, indicating Arrhenius behavior. The effects of the nature of electroactive solute molecules on Dapp, ks, and the half-wave potentials(E1/2) are discussed.展开更多
The ditheion coefficients(Dapp) and the heterogeneous electron-transfer rate constan(ks)for ferrocene in MPEG/salt electrolytes were determined by using Steady-stae voltammetry. The temperature dependence of the two p...The ditheion coefficients(Dapp) and the heterogeneous electron-transfer rate constan(ks)for ferrocene in MPEG/salt electrolytes were determined by using Steady-stae voltammetry. The temperature dependence of the two parameters obeys the Arrhenius equstion. The effect of the ionic size of sir supporting electrolytes on diffusion and electron transfer dynamics of fermcene was discussed展开更多
Studies on transition-metal catalyzed olefin-polar monomer coordination copolymerization and their resulting polar-functionalized polyolefin materials have attracted attention from both academia and industry.After dec...Studies on transition-metal catalyzed olefin-polar monomer coordination copolymerization and their resulting polar-functionalized polyolefin materials have attracted attention from both academia and industry.After decades of research,recent developments in a variety of high-performance catalytic systems have shown that this field is on the brink of industrialization.This review summarizes representative olefin-polar monomer coordination copolymerization catalyst systems that may be suitable for industrial polyolefin production via homogeneous solution-phase processes or heterogeneous gas-phase/slurry-phase processes.展开更多
文摘The Rouse-Zimm model with slippage was improved and the basic parameters of modelwere modified to explain the rheological properties of star-type branched polymersolutions. The theoretical results show good agreement with experimental data.
基金The authors appreciate the support from National Key Research and Development Program of China(NO.2022YFE0129900).
文摘The polymer solution flow in porous media is a central research topic related to hydraulic fracturing measures,formation damage and fracture propagation.Influenced by molecular weights and concentrations,various flow patterns of polymer in pores are presented,resulting in different filtration loss.In this work,the effectiveness of various polymer solutions for filtration loss was assessed by utilizing the core flooding experiment firstly.The result shows that lesser filtration loss normally is inextricably linked to solutions with high molecular weight and concentration.Subsequently,the flow behaviors of polymer solutions investigated by designed micro pore-throat structure and micro-particle image velocimetry(m-PIV)further confirmed the above result.It was found that the central convergent flow pattern benefiting from higher viscous force loss and less filtration loss was observed at high flow rates(0.5 mL/h),and higher molecular weight and concentration were more prone to convergent flow patterns.The viscosity force loss increases by about 4 times varying the molecular weight of polymer from 5×10^(6)to 18×10^(6)g/mol or the concentration from 0.05 to 0.3%.It interprets higher molecular weight and concentration in core studies and field observations with decreased filtration loss of HPAM.This work provides a theoretical foundation for the application of fracturing fluids as well as fresh perspectives on how to access the filtration loss of fracturing fluids.
基金from the National Natural Science Foundation of China(Nos.52005194,51635006,and 51675199)China Postdoctoral Science Foundatio n(No.2019M662615)+1 种基金the National Program on Key Basic Research Project(No.2019YFB1704900)the Fundamental Research Funds for the Central Universities’ HUST(No.2020JYCXJJ055).
文摘Entanglement network is an important structural feature in concentrated polymer solutions and polymer melts,which has a great influe nee on the transie nt rheological behavior and molecular con figurati on evolution.However,the existi ng constitutive models have limitations in describi ng the influe nee of dyn amic entan glement behavior on molecular chain motion,resulti ng in inaccurate descriptions of the transient rheological behavior.Thus,a molecular con figuration evoluti on model for polymer solutions considering the dyn amic entanglement effect is proposed by introducing an intermolecular force that changes with the orientation of the molecular chain in this work.The intermolecular force is introduced by consider!ng the friction coefficient as anisotropic,and the orientation effect is considered by introducing an excluded volume depende nt an isotropic diffusi on.The proposed model can better describe the stress relaxation,stress growth,and dielectric an isotropy of polymer soluti ons compared with the an isotropy FENE model and FENE model.In addition,the in fluence of different model parameters on the transient and steady shear response of polymer soluti on is investigated,and the results show that the in fluence of volume loss on the fricti on anisotropy factor k0 in creases as the solution concen tration in creases.
基金The authors gratefully a.cknowledge financial supportfrom th6 Natiol-al Natural Science Foundatiol- of CI-h-a. The number of
文摘Based on the molecular theory of non-linear viscoelasticity with constrained entanglements in polymer melts, the material functions in simple shear flow were formulated, the theoretical relations between and shear rate (), and topologically constrained dimension number and a were derived. Linear viscoelastic parameters and and topologically constrained dimension number and as a function of the primary molecular weight, molecular weight between entanglements and the entanglement sites sequence distribution in polymer chain were determined. A new method for determination of viscoelastic parameters G and topologically constrained dimension number a and and molecular weight and from the shear flow measurements was proposed. It was used to determine those parameters and structures of HDPE, making a good agreement between these values and those obtained by other methods. The agreement affords a quantitative verification for the molecular theory of nonlinear viscoelasticity with constrained entanglement in polymer melts.
文摘It is shown theoretically that the viscoelasticity of polymer melts is determined by three combining factorst they are the primary molecular weight and its distribution, the number of entanglement sites on polymer chain and the sequence distribution of constituent chains in entanglement spacings. A unified quantity for the three combing factors is the average constrained dimensional number of constituent chains in the long entanglement spacings (v). A new relation of v to the primary molecular weight and the number of testing polymers were derived from the multiple entanglement and reptation model, and a new method for determining v was proposed. The dependences of linear viscoelastic functions on the primary molecular weight and its distribution were derived by the statistical method. When Mn=6Me to 18 Me, the values of (v) can range from 3.33 to 3.70. Their values are in a good agreement with the experiment data, and it can slightjy vary with the different species of polymers and the different ranges of molecular weight of polymers
文摘An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results
基金The project was supported by National Natural Science Foundation of China(No.29774020).
文摘Critical association concentration (Ca) of ethylene-vinyl acetate copolymer (EVA) in selective solvent mixtures of 1,2-dichloroethane (DCE) (polar solvent) and cyclohexane (CYH) (non-polar solvent) was investigated. DCE is a good solvent for polyvinyl acetate (PVAc) and a poor solvent for paraffin, whereas CYH is a good solvent for the paraffin and a precipitant for PVAc. Viscosities of EVA in different compositions of the solvent mixture with and without additives were measured. Viscosity results were used to determine the C-A value of the systems. It is shown that C-A was markedly dependent on the composition of the solvent mixture and concentration and structure of the additive. Solvation and competition between hydrogen bonding and micellisation were suggested for qualitative description of the changing of C-A value observed.
基金financial support from the National Key Technology R&D Program in the 12th Five Year Plan of PetroChina (No: 2011ZX05010-003-02)the National Key Technology R&D Program in the 12th Five Year Plan of CNOOC (No: 2011ZX05024-04-05-03)
文摘Performance characteristics of partially hydrolyzed polyacrylamide (HPAM) and cross- linked polymer (CLP, Cr^3+ as the cross linker) solutions have been investigated. A Brookfield viscometer, rheometer, dynamic light scattering system, and core flow device have been used to measure the viscosity, viscoelasticity, polymer coil dimensions, molecular configuration, flow characteristics, and profile modification. The results show that, under conditions of high salinity and low HPAM and Cr^3+ concentrations, cross-linking mainly occurred between different chains of the same HPAM molecule in the presence of Cr^3+, and a cross-linked polymer (CLP) system with a local network structure was formed. Compared with an HPAM solution of the same concentration, the apparent viscosity of the CLP solution increased slightly or remained almost unchanged, but its viscoelasticity (namely storage modulus, loss modulus, and first normal stress difference) increased, and the resistance coefficient and residual resistance coefficient increased significantly. This indicates that the CLP solution exhibits a strong capability to divert the sequentially injected polymer flood from high-permeability zones to low- permeability zones in a reservoir. Under the same HPAM concentration conditions, the dimensions of polymer coils in the CLP solution increased slightly compared with the dimensions of polymer coils in HPAM solution, which were smaller than the rock pores, indicating that the cross-linked polymer solution was well adapted to reservoir rocks. Core flood experiments show that at the same cost of reagent, the oil recovery by CLP injection (HPAM-1, Cr^3+ as the cross linker) is 3.1% to 5.2% higher than that by HPAM- 2 injection.
基金This work was supported by the Chinese National Basic Research Project "Macromolecular Condensed State" and National Natural Science Foundation of China
文摘The concentration dependence of the reduced viscosity of dilute polymer solution is interpreted in the light of a new concept of the self-association of polymer chains in dilute solution. The apparent self-association constant is defined as the molar association constant divided by the molar mass of individual polymer chain and is numerically interconvertible with the Huggins coefficient. The molar association constant is directly proportional to the effective hydrodynamic volume of the polymer chain in solution and is irrespective of the chain architecture. The effective hydrodynamic volume accounts for the non-spherical conformation of a short polymer chain in solution and is a product of a shape factor and hydrodynamic volume. The observed enhancement of Huggins coefficient for short chain and branched polymer is satisfactorily interpreted by the concept of self-association. The concept of self-association allows us to predict the existence of a boundary concentration C-s(dynamic contact concentration) which divides the dilute polymer solution into two regions.
文摘The influence of dissolved oxygen content on the oxidative stability of a linked polymer solution (LPS) was studied by micro-filtration, dynamic light scattering and viscosity measurements. The results showed that at the same temperature, the degree of the oxidative degradation of the LPS increased and the rapidity of the oxidative degradation was accelerated with the increase of the dissolved oxygen content. Consequently, the size of linked polymer coils (LPCs) of the LPS became small, and the plugging capability of the LPS decreased. At a fixed content of dissolved oxygen, with increasing degradation temperature, almost the same results were observed, namely, an increased degree of oxidative degradation, accelerated rapidity of the oxidative degradation and decreased plugging capacity, with decreased oxidative stability of LPS. At 90 °C, in the presence of oxygen, LPS lost its plugging capability after having been degraded for a period of time. But at 40 °C, LPS with low dissolved oxygen content could be stable for a long time. The decreased plugging ability of LPS after oxidative degradation is mainly caused by the decreased size and number of the LPCs due to the breaking of hydrolyzed polyacrylamide (HPAM) molecule segments and the structural changing of HPAM molecules.
基金This work was supported by the National Basic Research Project-Macromolecular Condensed State,and the National Natural Science Foundationof China
文摘Careful measurements of the dilute solution viscosities of polyethylene glycol and polyvinyl alcohol in water were carried out. The reduced viscosities of both polymer solutions plot upward curves at extremely dilute concentration levels similar to the phenomena observed for many polymer solutions in the early 1950's. Upon observation of the changes of the flow times of pure water in and the wall surface wettability of the viscometer after measuring solution viscosity, a view was formed that the observed viscosity abnormality at extremely dilute concentration regions is solely due to the effect of adsorption of polymer chains onto the wall surface of viscometer. A theory of adsorption effect based on the Langmuir isotherms was proposed and a mathematical; analysis for data treatment was performed. The theory could adequately describe the existing viscosity data. It seems necessary to correct the viscosity result of dilute polymer solutions measured by glass capillary viscometer by taking into account the effect of adsorption in all cases.
文摘The diffusion coefficients(Dapp) and the heterogeneous electron transfer rate constants(ks)for ferrocene in several polymer solvents were determined by using steady-stae voltammetry. Thetemperature dependence of the two parameters indicates Arrhenius behavior. The polymer solventeffects on diffusion and electron transfer dynamics of ferrocene were discussed
基金This work was supported by the National Key Project for Fundamental Research"Macromolecular Condensed State",The State Science and Technology Commission of China
文摘The statistical counting method for the computer simulation of the thermodynamic quantities of polymer solution has been reviewed. The calculating results for a single athermal chain confirm the theory of the renormalization group. The results for the athermal solution are consistent with the scaling law of the osmotic pressure with the exponent 2.25. The results for a single chain with the segmental interaction are in a good agreement with the exact results obtained by the direct counting method. The results for the polymer solution show us that the Flory-Huggins parameter is strongly dependent on both the polymer concentration and the interaction energy between segments. (Author abstract) 15 Refs.
基金Supported by the National Natural Science Foundation of China(Nos.20574069,20490220,50303017,50373044and50340420392)Programs of the Chinese Academy of Sciences(No.KJCX2-SW-H07)the National Basic Research Program ofChina(No.2003CB615600).
文摘The calculations presented in this paper are based on the Sanchez-Lacombe(SL)lattice fluid theory.The interaction energy parameter,g12/k,required in this approach was obtained by fitting the cloud points of polystyrene(PS)/methylcyclohexane(MCH)polymer solutions under pressure.The SL lattice fluid theory was used to calculate the spinodals,the binodals,and the Flory-Huggins(FH)interaction parameter of the solutions.The calculated results show that the SL lattice fluid theory can describe the dependences of thermodynamics of PS/MCH solutions on temperature and pressure very well.However,the calculated enthalpy and the excess volume changes indicate that the Clausius-Clapeyron equation cannot be suitable to describe pressure effect on PS/MCH solutions.Further analysis on the thermodynamics of this system under pressure shows that the role of entropy is more important than the excess volume in the present case.
基金supported by the National High Technology Research and Development Program of China(863 Program,2007AA090701)the National Basic Research Program of China(2010CB735505)
文摘The microscopic oil displacement mechanism in viscoelastic polymer flooding is theoretically analyzed with mechanical method.The effects of viscoelasticity of polymer solution on such three kinds of residual oil as in pore throat,in sudden expansion pore path,and in dead end are analyzed.Results show that the critical radius of mobile residual oil for viscoelastic polymer solution is larger than that for viscous polymer solution,which makes the oil that is immobile in viscous polymer flooding displaced under the condition of viscoelastic polymer solution.The viscous polymer solution hardly displaces the oil in dead ends.However,when the effect of viscoelasticity is considered,the residual oil in sudden expansion pore paths and dead ends can be partly displaced. A dimensionless parameter is suggested to denote the relative dominance of gravity and capillary pressure.The larger the dimensionless parameter,the more accurate the increment expressions.
基金The authors are grateful to the National Natural Science Foundation of China (No. 50433040) for the financial support.
文摘Low molecular weight poly(glycidyl methacrylate)s (PGMAs) were prepared by photopolymerization in ethyl acetate, with benzophenone (BP) as photoinitiator, and triethylamine (TEA) as hydrogen donor. The existence of semipinacol dormant end groups in PGMA was confirmed by FT-IR and ^1H-NMR, and the content of the semipinacol dormant groups was determined quantitatively by ^1H-NMR measurement. The effects of various thctors, such as reaction time, BP concentration and monomer concentration on the synthesis of the polymers were investigated systematically. The molecular weights of the polymers were also investigated with GPC. It is shown that increasing BP concentration and decreasing irradiation time and monomer concentration led to a significant decrease of the molecular weights.
文摘This paper mainly deals with the design and synthesis of a novel styrene-butadieneblock copolymer. When this copolymer is used in the tread portion of tyres, it can improvewet skid resistance and reduce rolling resistance without sacrificing its general physical-mechanical properties. The visco-elastic curve of tire tread using the novel copolymer asits rubber portion was showed. Reactivity ratios for two monomers in the polymerizingsystem were calculated. The diagrams of differelitial, integral and finite difference calculithroughout the whole molecular chain were presented. The influence of the micro- andmacro-structure of the copolymer chain on wet skid resistance and rolling resistance wasdiscussed
文摘The diffusion coefficients(Dapp) and the heterogeneous electron-transfer rate constants(ks)for ferrocene and its seven derivatives in MPEG/LiClO4 electrolyte were determined by using steadystate voltammetry. The two parameters increase with increasing temperature, indicating Arrhenius behavior. The effects of the nature of electroactive solute molecules on Dapp, ks, and the half-wave potentials(E1/2) are discussed.
文摘The ditheion coefficients(Dapp) and the heterogeneous electron-transfer rate constan(ks)for ferrocene in MPEG/salt electrolytes were determined by using Steady-stae voltammetry. The temperature dependence of the two parameters obeys the Arrhenius equstion. The effect of the ionic size of sir supporting electrolytes on diffusion and electron transfer dynamics of fermcene was discussed
基金supported by the National Key R&D Program of China(grant no.2021YFA1501700)the National Natural Science Foundation of China(grant nos.52025031,22001004,52373002,U1904212,and 52203016).
文摘Studies on transition-metal catalyzed olefin-polar monomer coordination copolymerization and their resulting polar-functionalized polyolefin materials have attracted attention from both academia and industry.After decades of research,recent developments in a variety of high-performance catalytic systems have shown that this field is on the brink of industrialization.This review summarizes representative olefin-polar monomer coordination copolymerization catalyst systems that may be suitable for industrial polyolefin production via homogeneous solution-phase processes or heterogeneous gas-phase/slurry-phase processes.