The effect of additives,solvent type,and polymer concentration on macromolecule dimensions

An equation is derived to estimate the hydrodynamic volume occupied by a typical linear polymer molecule, knowing only the polymer molecular weight and concentration of polymer in the solution. This equation may be applied to solutions above a minimum polymer concentration. Accuracy of the equation is determined by comparing it to an established method of calculating macromolecule dimensions. Above dilute solution conditions, the volume pervaded by a macromolecule is affected mainly by the polymer molecular weight and concentration of polymer in the solution. Chain dimensions are generally unaffected by the type of polymer, solvent, or additive in the solution.     

油藏流动条件下聚合物溶液老化规律研究

根据聚合物溶液在地层中的运移过程,设计了聚合物溶液的动态老化实验以研究新老聚合物溶液混合下的动态老化过程。实验结果表明:聚合物溶液的混合老化过程与以往的静态老化过程类似,因此传统的静态老化过程可以用于近似聚合物溶液运移过程中的动态老化过程。通过数据分析,提出了混合后聚合物溶液粘度的估算方法。并在此基础上,给出了相应的数值模拟思路。     

A method for determination of thermodynamics and solubility parameters of polymers in dilute solutions from critical volume fractions

An equation using the critical volume fraction and segment number of polymer was proposed for the partial molar entropy change of a polymer for mixing in dilute solution. The partial molar enthalpy change of polymer for mixing was determined from the thermodynamic equilibrium property of two polymer phases at the critical temperature. The solubility or cohesion parameter of a polymer fraction at the critical temperature was calculated by using the partial molar enthalpy change and repeat unit volume of the polymer. The solubility parameter of high molar mass polymer at the theta temperature was determined by extrapolating solubility parameter values of the polymer fractions to high molar mass by using the solubility parameter-segment number relation of polymer fraction. This relation gives good straight line. The solubility parameter of the polymer at the theta temperature and the exchange energy parameter for polymer-solvent pair were obtained directly from the intercept and the slope of this line, respectively. These equations were applied to the critical point data of polystyrene (PS) in methylcyclohexane (MCH) and in cyclohexane (CH) solutions. The results obtained in this study coincide with the literature values for the solubility parameter of PS and exchange energy parameter for PS in CH solution. It was also found that the partial molar entropy change of a polymer for mixing at theta temperatures has about a constant value.     

A survey of dual phase continuity and miscibility in interpenetrating polymer networks,making use of selective decrosslinking and dissolution of one component: Poly(n-butyl acrylate)/polystyrene

A sequential interpenetrating polymer network, IPN, may be defined as a combination of two polymers in network form, at least one of which was polymerized or crosslinked in the presence of the other. Two major problems of interest to sequential IPN's relate to phase continuity and extent of mixing within each phase. A first attempt to define the molar volume of a network is made in terms of the molar volume of the polymer between crosslinks. This permits a thermodynamic calculation of the changes in molecular mixing expected as a function of crosslink density. The experimental system was poly(n-butyl acrylate)/polystyrene IPN's, where the PnBA was crosslinked with acrylic acid anhydride. This last may be selectively hydrolyzed, forming a semi-IPN, and then the PnBA can be extracted. Scanning electron microscopy and dynamic mechanical spectroscopy were carried out at each stage.     

A method for determination of thermodynamic and solubility parameters of polymers from temperature and molecular weight dependence of intrinsic viscosity

An equation using the temperature dependence of intrinsic viscosity of a polymer was proposed for the determination of the partial molar entropy and enthalpy changes of the polymer for mixing in dilute solution. It was found that the partial molar entropy change of a polymer for mixing at a given temperature is proportional to the hydrodynamic volume or segment number of the polymer. The partial molar enthalpy change of the polymer for mixing was determined from the thermodynamic equilibrium property of polymer phases. The solubility or cohesion parameter of a polymer fraction was calculated by using the partial molar enthalpy change and repeat unit volume of the polymer. The solubility parameter of high molar mass polymer at a given temperature was determined by extrapolating solubility parameter values of polymer fractions to high molar mass by using the solubility parameter-segment number relation of polymer fraction. This relation gives a straight line. The solubility parameter of the polymer at a given temperature and the effective interchange energy parameter for polymer-solvent pair were obtained directly from the intercept and the slope of this line, respectively. These equations were applied to the intrinsic viscosity-temperature data of polystyrene fractions in decalin solutions, and polystyrene fractions in decalin, cyclohexane and dioctyl phthalate solutions at the theta temperatures and in toluene solutions at the given temperatures. The results obtained in this study coincide with the literature values. In addition, it was given a relation, which is derived from the blob theory for the temperatures above the theta point, for the estimation of the thermodynamic parameters of polymers for mixing.     

聚合物搅拌脱挥设备及其CFD模拟研究进展

综述了聚合物搅拌脱挥设备的开发进展,分析了设备开发过程存在的关键问题。指出卧式脱挥设备中的流动特性、混合特性、成膜特性以及表面更新特性等是强化传质的关键因素,具有自清洁搅拌特性的高效卧式脱挥设备是装备开发与研究的主要方向。阐述了计算流体力学(CFD)在研究高黏流体卧式搅拌设备内传递过程机理中的应用。基于网格重叠技术的有限元方法和基于动网格的有限体积方法可以解决复杂几何结构的桨叶和翅片、双轴的旋转运动以及啮合机构非常小的间隙等难题。借助于CFD中VOF多相流模型可以精确地追踪气液相界面,模拟反应器中的成膜过程和表面更新特性,进而可以深入分析设备中的传质过程,为高效聚合物脱挥设备的优化与设计提供了新的思路。     

The heating process in dissolving cellulose xanthate in an apparatus of the screw type

Conclusions Rheological constants of viscose have been determined which make it possible to describe mathematically the anomalous portion of the flow curves and the temperature dependence of viscose viscosity, and also are necessary for calculating the technological parameters of the process of continuous dissolution of cellulose xanthate and to construct apparatus.The possibility of calculating the heat-up of viscose after treatment in continuous dissolvers and of selecting a continuous solution regime at an assigned temperature for the exiting viscose from calculation relationships has been demonstrated.The advisability of simultaneously carrying out the processes of solution and heating of the viscose in continuous apparatus has been established.Translated from Khimicheskie Volokna, No. 2, pp. 28–30, March–April, 1990.     

Flory溶液理论中待定参数的决定

用反相色谱法(IGLC)测定聚合物和溶剂的相互作用参数X,推算出Flory聚合物溶液理论中的交换能参数X_(12),结合本文估算的聚合物和溶剂的接触表面之比S_1/S_2,计算了聚二甲基硅氧烷(PDMS)、天然橡胶(NR)、聚苯乙烯(PS)和聚异丁烯(PIB)等溶液体系中,X和聚合物链节分率φ_2的关系,结果能与实验值很好符合,并且还计算了溶液的体积变化V~(?)/V~(?)和无限稀混合焓△H_(?)~∞.     

Optimized Synthesis of Salicylate-based Poly( anhydride-esters)

Summary The synthesis of a salicylate-based poly(anhydride-ester) was optimized to improve the overall efficiency and quality of the polymer. First, a new approach for the preparation of the polymer precursor minimizes the overall number of synthetic steps and increases the overall yield. Second, the melt-polymerization apparatus was modified to include dynamic mixing, which yields polymer with increased molecular weights on both the milligram and gram scale. Received: 2 October 2002/Accepted: 6 January 2003 Correspondence to Kathryn E. Uhrich     

Mathematical description of the synthesis of butadiene rubber with allowance for the branching of a polymer under conditions of the separate supply of a reaction mixture to the reactors of a cascade

Mathematical modeling of the synthesis of butadiene rubber on a neodymium-based catalytic system under conditions of the separate supply of a reaction mixture to the apparatuses of a cascade is performed. Expressions are derived for calculating the characteristics of the branching of the polymer with allowance for the additional supply of the reaction mixture to the second apparatus of the cascade. An analysis of the influence of the flow rate of an additional stream of the reaction mixture to the second apparatus of the cascade and operating parameters on the molecular weight characteristics and branching of the polymer is performed.     

Modelling the effects of imperfect mixing on the performance of anaerobic reactors for sewage sludge treatment

An approach to the modelling of suspended-growth anaerobic digestion systems based on the assumption of an incompletely mixed reactor is presented. The mathematical model developed describes the dynamic behaviour of anaerobic sludge digesters under non-ideal mixing conditions. The microbial kinetic model for the anaerobic digestion of waste-activated sludge distinguishes the processes of death and lysis of activated sludge cells, hydrolysis of particulate material, fermentation of soluble substrates, volatile fatty acids utilisation and methane formation. The interaction of two microbial groups is considered, i.e. acid-formers and methanogens. Their growth is assumed to depend on Monod kinetics for the substrates. Death and lysis, hydrolysis and biomass decay are described by first order reactions. The biokinetic expressions were linked to a simple mixing model which considered the reactor volume split into two sections: the flow-through and the retention regions. The transfer of material between regions was assumed to be limited. Deviations from an ideal completely mixed regime were represented by changing the relative volume of the flow-through region (α) and the turnover time of material in the vessel (τ). The dynamic model described the effects of the retention time and reactants' distribution, resulting from the mixing condition, on process performance. Computer simulations under different conditions showed a considerable decline in methane production and treatment efficiency due to incomplete mixing. The COD removal efficiency increased by extending the retention time and the degree of mixing. The evaluation of the impact of the mixing parameters showed that α has a far more significant effect on the performance of anaerobic digestion than τ does. Nevertheless, both are important and the overall efficiency is a complex function of both parameters. The results obtained confirm and emphasise the importance of considering mixing when simulating anaerobic digestion, calculating process conversion efficiency, and during anaerobic reactor design. © 1998 SCI.     

Computer-aided phase modulated flow birefringence experiment on polystyrene solutions

A rheo-optical experimental apparatus based on Phase Modulated Flow Birefringence (PMFB) method has been developed. This PMFB method is one of the most powerful techniques to study the rheological behaviors of a polymer system. An useful computer-aided system which has the capability of controlling the flow dynamics, signal detections and data acquisitions for the PMFB method has been developed. Also a newly modified mathematical calculation method to obtain the birefringence with less error propagations has been established. This computerized system for PMFB technique was carefully checked by the quarter wave plate calibration procedure and was proved to be reasonable for obtaining the rheo-optical properties of the polymer liquids. Also, with the PMFB method, an experiment for investigating the effects of molecular weight on the rheological properties of 1.5 wt% of polystyrene solutions was carried out. The experimental results were in good agreement with the general viscoelastic properties of the polymer solution and with the other experimental results reported so far.     

Generalized Flory–Huggins model for heat‐of‐mixing and phase‐behavior calculations of polymer–polymer mixtures

An extended and generalized Flory–Huggins model for calculating the heats of mixing and predicting the phase stability and spinodal diagrams of binary polymer–polymer mixtures is presented. In this model, the interaction parameter is considered to be a function of both temperature and composition. It is qualitatively shown that the proposed model can calculate the heats‐of‐mixing curves containing exothermic, endothermic, and S‐shaped or sigmoidal types and predict the spinodals, including the upper and lower critical solution temperatures, and closed‐loop miscibility regions. Using experimental results of analog calorimetry for four polymer mixtures of polystyrene/poly(vinyl chloride) (PS/PVC), polycarbonate (PC)/poly(ethylene adipate) (PEA), polystyrene/poly(vinyl acetate) (PS/PVAc), and ethylene vinyl acetate copolymer (EVA Co)/chlorinated polyethylene (CPE), the capabilities of the proposed functionality for the interaction parameter was studied. It is shown that this function can be used satisfactorily for the heat‐of‐mixing calculations and phase‐behavior predictions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1328–1340, 2000     

A NEW METHOD OF CALCULATING TERNARY MASS TRANSFER WITH A NON TRANSFERRING SPECIES BASED ON GILLILAND'S PARAMETRIC SOLUTION OF THE MAXWELL-STEFAN EQUATIONS FOR THE FILM MODEL

This paper presents a solution for the problem of multiple roots in Gilliland's parametric solution of the Maxwell-Stefan equations. Based on it a new algorithm for calculating ternary mass transfer with a non transferring species is obtained. This new algorithm demonstrates rapid and stable convergence. In contrast to the well known calculation of mass transfer in multicomponent mixtures using the matrix solution of the Maxwell-Stefan equations the new algorithm simplifies the calculation by avoiding any matrix operations.     

微孔发泡过程中脉动剪切对聚合物/超临界 CO2均相体系形成的影响

提出一种聚合物／超临界CO2均相体系快速形成的新方法——将振动力场引人到发泡过程，在简单剪切的基础上垂直叠加一个脉动剪切场，考察了该方法对均相体系形成的影响。实验材料用聚苯乙烯(PS)，用自行设计的电磁动态发泡模拟机，了不同剪切速率、振动力场及混合时间对聚合物／超临界CO2均相体系形成的影响。结果表明，随着剪切速率的增加，聚合物和气体的混合程度明显增强；而振动力场的引入进一步增强了剪切混合的效果，使聚合物／超临界CO2均相体系能够在较短的时间内形成。     

Crystallization studies on deformed polybutene-1 melts

An apparatus was designed and built which allowed an investigation concerning the morphology and kinetics of crystallization of a deformed polybutene-1 melt. The polymer was quenched from a temperature above its melting point to one of two crystallization temperatures. The supercooled melt was then sheared and allowed to crystallize isothermally while the internal stress in the melt was continuously recorded. A polarizing microscope was employed for the simultaneous study of the resulting morphological changes. By properly accounting for thermal contractions within the apparatus caused by the quenching operation, as well as the imposed shear strain, a strain history of the polymer during crystallization was developed. From this strain history and the assumption that the volume contraction resulting from crystallization was isotropic, approximate kinetics of crystallization in a deformed polymer melt were determined.     

PSRK模型的修正混合规则及其应用于聚合物溶液汽液平衡的预测

To extend the PSRK(predictive Soave-Redlich-Kwong equation of state)model to vapor-liquid equilibria of polymer solutions,a new EOS-gE mixing rule is applied in which the term ∑ xi ln(b/bi)in the PSRK mixing rule for the parameter a,and the combinatorial part in the original universal functional activity coefficient(UNIFAC)model are cancelled.To take into account the free volume contribution to the excess Gibbs energy in polymer solution,a quadratic mixing rule for the cross co-volume bij with an exponent equals to 1/2 is applied [b1/2 ij= 1/2(b1/2 i b1/2 j)].The literature reported Soave-Redlich-Kwong equation of state(SRK EOS)parameters of pure polymer are employed.The PSRK model with the modified mixing rule is used to predict the vapor-liquid equilibrium(VLE)of 37 solvent-polymer systems over a large range of temperature and pressure with satisfactory results.     

丁二烯气相聚合过程中聚合物颗粒增长的动态研究

An experimental apparatus composed of microscope, video camera, image-processing, and mini reactor which can be used for real-time measurement of the growth of polymer particle in gas phase polymerization was built up to carry out dynamic study of gas phase polymerization of butadiene by heterogeneous catalyst based on neodymium(Nd). The studies of the shape duplication of polymer particles and catalyst particles and the growth rate of polymer paxticle were made. Results show that the appaxatus and procedure designed can be well utilizedto make dynamic observation and data collection of the growth of polymer particle in gas phase polymerization.A phenomenon of shape duplication of polymer particles and catalyst particles was observed by the real-time measurement. The result also concludes that the activity of individual catalyst particle is different, and the effect of reaction pressure on the growth of polymer particle is significant.     

THE EFFECT OF IMPERFECT MIXING ON POLYMER QUALITY IN LOW DENSITY POLYETHYLENE VESSEL REACTORS

A mathematical model is developed for the calculation of polymer quality in low density polyethylene vessel reactors, taking into account mixing limitations at the initiator feed point. Model predictions show that imperfect mixing in the reactor can produce considerable variations in polymer molecular weight distribution. The effect of the most important process conditions, input feed temperature, solvent concentration, monomer flow rate and initiator type, on the final polymer quality is analyzed. The advantages of the design solution which divides the reactor in more compartments in series are also discussed.     

THE EFFECT OF IMPERFECT MIXING ON POLYMER QUALITY IN LOW DENSITY POLYETHYLENE VESSEL REACTORS

A mathematical model is developed for the calculation of polymer quality in low density polyethylene vessel reactors, taking into account mixing limitations at the initiator feed point. Model predictions show that imperfect mixing in the reactor can produce considerable variations in polymer molecular weight distribution. The effect of the most important process conditions, input feed temperature, solvent concentration, monomer flow rate and initiator type, on the final polymer quality is analyzed. The advantages of the design solution which divides the reactor in more compartments in series are also discussed.