改进的催化剂的乙烯聚合动力学研究

The study concerns the use of MgCl2-supported high-activity Ziegler-Natta catalysts for the polymerization of ethylene. In particular, two types of catalysts were investigated, which were N-catalyst (BRICI) and improved polyethylene catalyst. The effects of catalyst structure on kinetic behavior were examined. The distribution of active centers in these catalysts was investigated by energy dispersive analysis by X-rays (EDAX), and morphologies of catalyst particles and polymer products were examined by scanning electron microscope (SEM). Hydrogen response and copolymerization performance were investigated and compared with the two catalysts. The results were correlated with the kinetic behavior of the two catalysts and appropriate models for polymer particle growth were presented. The improved polyethylene catalyst showed higher activity, better hydrogen response and copolymerization performance.     

RHEOLOGICAL BEHAVIOR OF POLYMER MELTS (I) UNIFIED MOLECULAR THEORY OF NON-LINEAR ISCOELASTICITY WITH CONSTRAINTS OF GAUSSIAN CHAIN ENTANGLEMENT FOR POLYMER MELTS

An approach with statistical mechanics and a unified molecular theory of non-linearviscoelasticity with constraints of Gaussian chain entanglement for polymer melts were proposed.Amultimode model structure for a single polymer chain with tail segments and N reversibleentanglement sites on the test polymer chain was developed.The probability distribution function ofthe end-to-end vector for a single polymer chain at entangled state and the viscoelastic free energyof deformation for polymer melts were calculated.Four types of stress-strain relationship and mem-ory function were derived from this theory.The above theoretical relationships were verified by experi-mental data of PS(polystyrene)and LDPE(low density polyethylene)melts.     

RHEOLOGICAL BEHAVIOR OF POLYMER MELTS (Ⅰ)UNIFIED MOLECULAR THEORY OF NON-LINEAR ISCOELASTICITY WITH CONSTRAINTS OF GAUSSIAN CHAIN ENTANGLEMENT FOR POLYMER MELTS

An approach with statistical mechanics and a unified molecular theory of non-linearviscoelasticity with constraints of Gaussian chain entanglement for polymer melts were proposed.Amultimode model structure for a single polymer chain with tail segments and N reversibleentanglement sites on the test polymer chain was developed.The probability distribution function ofthe end-to-end vector for a single polymer chain at entangled state and the viscoelastic free energyof deformation for polymer melts were calculated.Four types of stress-strain relationship and mem-ory function were derived from this theory.The above theoretical relationships were verified by experi-mental data of PS(polystyrene)and LDPE(low density polyethylene)melts.     

预分布管内流场的CFD模拟及实验验证(英文)

Liquid distributor is a very import internal for distillation columns. Pre-distributor is usually set on the top of distributor for initial distribution. Fluid flow in pre-distributor is a complex system of variable mass flow with many orifices and sub-branches. Consequently, the two phase modeling of pre-distributors was carried out and the homogeneous model with free surface model was applied. The numerical method was validated by comparing with experimental data. Using the simulated results for different pre-distributors, the impacts of inflow rate, location and orientation upon the outflow distribution were investigated. Furthermore, influences of the outflow distribution for pre-distributor on liquid uniformity in trough were also analyzed. The conclusions can be adopted for the struc-tural design of liquid distributor and pre-distributor of large scale.     

Fabrication of high-capacity cation-exchangers for protein adsorption: Comparison of grafting-from and grafting-to approaches

In this work, we have synthesized two polymer-grafted cation exchangers: one via the grafting-from approach, in which sulfopropyl methacrylate (SPM) is grafted through atom transfer radical polymerization onto Sepharose FF (the thus resulting exchanger is referred as Sep-g-SPM), and another via the grafting-to approach, in which the polymer of SPM is directly coupled onto Sepharose FF (the thus resulting exchanger is called as Sep-pSPM). Protein adsorption on these two cation exchangers have been also investigated. At the same ligand density, Sep-g-SPM has a larger accessible pore radius and a smaller depth of polymer layer than Sep-pSPM, due to the controllable introduction of polymer chains with the regular distribution of the ligand. Therefore, high-capacity adsorption of lysozyme and γ-globulin could be achieved simultaneously in Sep-g-SPM with an ionic capacity (IC) of 308 mmol·L^-1. However, Sep-pSPM has an irregular chain distribution and different architecture of polymer layer, which lead to more serious repulsive interaction to proteins, and thus Sep-pSPM has a lower adsorption capacity for γ-globulin than Sep-g-SPM with the similar IC. Moreover, the results from protein uptake experiments indicate that the facilitated transport of adsorbed γ-globulin occurs only in Sep-pSPM and depends on the architecture of polymer layers. Our research provides a clear clue for the development of high-performance protein chromatography.     

甲基丙烯酸-N, N-2-甲基乙胺酯原子转移自由基聚合动力学研究

A kinetic model was developed to describe the atom transfer radical polymerization (ATRP) of 2-(N,N-dimethylamino) ethyl methacrylate (DMAEMA). The model was based on a polymerization mechanism, which included the atom transfer equilibrium for primary radical, the propagation of growing polymer radical, and the atom transfer equilibrium for the growing polymer radical. An experiment was carried out to measure the conversion of monomer, the number-average molecular weight of polymer and molecular weight distribution for the ATRP process of DMAEMA. The experimental data were used to correlate the kinetic model and rate constants were obtained. The rate constants of activation and deactivation in the atom transfer equilibrium for primary radical are 1.0 × 104 L·mol-1·s-1 and 0.04L·mol-1·s-1, respectively. The rate constant of the propagation of growing polymer radical is 8.50L·mol-1·s-1, and the rate constants of activation and deactivation in the atom transfer equilibrium for growing polymer radica     

稀土催化苯乙烯本体聚合机理与动力学

The bulk polymerization of styrene catalyzed by Nd(P204)3/MgBu2/HMPA (hexamethyl phospho-ramide) was carried out in capped glass tubes. The effects of reaction conditions on polymerization conversion and molecular weight in the range of high conversion were investigated. The molecular weight of the resultant polymers is dramatically high and its distribution is relatively narrow. The polymerization process demonstrates the feature of living polymerization and auto-acceleration phenomenon. The auto-acceleration phenomenon is attributed to the non-instantaneous formation of the active species. The experimental data suggest that chain transfer to MgBu2 is one of the factors governing the molecular weight development. A mechanism of polymerization is presented with the chain transfer process incorporated.     

RHEOLOGICAL BEHAVIOR OF POLYMER MELTS (II) MULTIPLE ENTANGLEMENT MODEL FOR PREDICTING THE DEPENDENCE OF VISCOELASTIC BEHAVIOR ON DEFORMATION STATE AND PRIMARY MOLECULAR WEIGHTS AND THEIR DISTRIBUTION

In accordance with the memory function of Gaussian chain constraints in entangled polymermelts a set of material functions related to a certain"test flow"are formulated from the O-W-Ftype constitutive equation by the appropriate selection of the Cauchy-Green and Finger tensors.Thedependences of these material functions on the strain rate and the dependences of the linearviscoelastic functions on the primary molecular weight distribution and the entanglement sites sequencedistribution on polymer chain are derived from a multiple-entanglement model and a couple of mech-anisms of relaxation for the loop and terminal entanglement sites.When the primary polymer chainsare modelled with the Lansing-Kraemer molecular distribution function,a set of new relationshipsamong linear viscoelastic functions(η_0,ψ_(10)~0,η_(ext)~0 and τ_1)and the molecular weights and their distributionare formulated.These functions and relationships are verified with experimental data.     

RHEOLOGICAL BEHAVIOR OF POLYMER MELTS (Ⅱ) MULTIPLE ENTANGLEMENT MODEL FOR PREDICTING THE DEPENDENCE OF VISCOELASTIC BEHAVIOR ON DEFORMATION STATE AND PRIMARY MOLECULAR WEIGHTS AND THEIR DISTRIBUTION

In accordance with the memory function of Gaussian chain constraints in entangled polymermelts a set of material functions related to a certain"test flow"are formulated from the O-W-Ftype constitutive equation by the appropriate selection of the Cauchy-Green and Finger tensors.Thedependences of these material functions on the strain rate and the dependences of the linearviscoelastic functions on the primary molecular weight distribution and the entanglement sites sequencedistribution on polymer chain are derived from a multiple-entanglement model and a couple of mech-anisms of relaxation for the loop and terminal entanglement sites.When the primary polymer chainsare modelled with the Lansing-Kraemer molecular distribution function,a set of new relationshipsamong linear viscoelastic functions(η_0,ψ_(10)~0,η_(ext)~0 and τ_1)and the molecular weights and their distributionare formulated.These functions and relationships are verified with experimental data.     

Preparation of an amphoteric flocculant having both high polymer content and low viscosity and its polymerization kinetics

It is not easy for liquid cationic flocculant diallyldimethyl-ammonium chloride(DM) homopolymer to simultaneously exhibit both low viscosity and high polymer content, which limited its application in offshore oilfield.In this paper, sodium allylsulfonate(XS) and sodium formate were used in the aqueous solution polymerization of DM.An amphoteric flocculant(PDMXS) with the properties of high polymer content(about 55 wt%) and low viscosity(efflux time measured by an Apply 4 viscometer was less than 100 s) was prepared.The optimum reaction conditions were identified as follows: the mass ratio of XS/DM was 10 wt%, the concentration of sodium formate was 2000 mg·L~(-1), reaction temperature was 55 ℃, the concentration of KPS was 0.5 wt% and the reaction time was 4 h.The polymerization kinetics was discussed.The results showed that R_p∝ [M]~(1.97)[I]~(0.68)[CTA]~(0.71) and the apparent activation energy was 72.55 kJ·mol~(-1).     

共缩聚反应中链段序列长度调控的分子模拟研究

利用分子模拟研究了共缩聚反应得到的高分子链上的嵌段长度分布。通过控制参加反应的两种组分的浓度比和共聚单体的反应活性,可得到与理论值差别很大的序列分布。有助于合成嵌段长度可控的共聚高分子。     

丁二烯气相聚合产物分子量分布和粒径分布模型研究

对非均相催化的丁二烯气相聚合,基于聚合物多层模型,考虑催化剂颗粒间活性位初始浓度和粒径分布对聚合物分子量分布和粒径分布的影响,建立了聚合物分子量分布和粒径分布的数学模型。模拟了反应温度、催化剂颗粒间活性位初始浓度和粒径分布等因素的影响,结果表明。随着温度升高,聚合物颗粒平均粒径变小,粒径分布变窄,聚合物分子量变小,分子量分布变宽;催化剂颗粒间的活性组分负载越均匀,聚合物分子量越大,分子量分布和粒径分布越窄;随着催化剂平均粒径变大,聚合物分子量变小,分子量分布变宽,不存在催化剂颗粒粒径分布和聚合物颗粒粒径分布间的复制现象。模型模拟结果与实验结果吻合较好,可用于预测丁二烯气相聚合产物的分子量、分子量分布和粒径分布。     

聚合反应周期进料对分子量分布可控性分析

对聚合产品的分子量分布实现在线控制是保证高分子产品质量的重要任务。以实验室规模的乙烯基丁基醚管式阳离子聚合反应为研究对象,验证了单体、引发剂周期进料对分子量分布有加宽效应,并从混合平均分布的角度研究了周期进料对分子量分布的影响,从而分析了实现分子量分布控制的可行性。     

多分散聚合物稀溶液体系的Rouse模型

本文将Rouse提出的均一分布球簧链式分子模型加以推广.得到了多分散体系的本构方程.对几种最常见的分子量分布,在稳态剪切流中,分别计算了它们的物质函数以及特性粘数与重均聚合度的关系.结果表明,这一线性模型的流变性质与聚合物的分子量分布有密切的关系;若通过物质函数的监测,则还能预示聚合反应的动态过程.     

Semibatch styrene suspension polymerization processes

Emulsion and suspension polymerization processes have widely been studied for more than 40 years. Although both polymerization processes are performed in heterogeneous media, each one presents its own typical characteristics, such as the particle size distribution, molecular weight distribution, polymer particle nucleation rate, and polymerization rate. In this study, semibatch styrene suspension polymerizations were carried out with feed compositions typical of emulsion processes. The initial reactor charge resembled the recipe of standard styrene suspension polymerizations, and the emulsion polymerization constituents were added during the batch. The influence of the moment at which the emulsion feed was started on the course of the polymerization and the effects of the feed on the polymer properties were analyzed. The polymer particle morphology and the average molecular weights changed very significantly with the emulsion feed time, and the changes could lead to the production of broad molecular weight distributions. Core–shell polymer particles could also be obtained, with the core being formed of polymer particles originating from the suspension polymerization process and the shell being formed of polymer particles originating from the emulsion polymerization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3021–3038, 2003     

Prediction of molar mass distribution,number and weight average degree of polymerization and branching of low density polyethylene

An extended mathematical model of an autoclave reactor for the high pressure polymerization of ethylene is presented. It allows one to predict not only the conversion but also the molar mass distribution, short and long chain branching, number and weight average degree of polymerization as a function of the synthesis conditions. The model includes the initiation step, chain growth, chain termination by disproportionation and combination, chain transfer to the monomer, polymer and modifier, and intramolecular chain transfer in the polymer radical. Number and weight average degrees of polymerization were computed by means of generating functions. For the calculation of the molar mass distribution recursion formulae are given. The performance of the model is shown by the good agreement of the predicted values with the experimental data.     

Non-steady-state model for kinetics of free radical polymerization, 3. Direct photo-initiation

The non-steady-state kinetics of directly photo-initiated polymerization were studied theoretically. Taking account of the facts that the amount of monomer consumed in propagation is much more than that in initiation for a process producing high polymer and that the rate constant of chain termination is much larger than that of chain propagation or transfer, a few very close approximations were adopted to solve the set of kinetic differential equations of the polymerization under consideration. The inexplicit function method developed in a previous paper of this series for the derivation of the molecular weight distribution function is still valid in this work. Some numerical computation was implemented to show the tendency of free radical concentration decay and the plots of molecular size distribution.     

乳液聚合瞬时乳胶粒大小和分布及其控制策略

乳液聚合中瞬时乳胶粒大小及分布与乳胶粒的形成和增长紧密相关,本文在苯乙烯,醋酸乙烯酯乳液聚合中考察了瞬时乳胶粒大小及分布。结果表明,在成核和稳定期乳胶粒增长速率较高,是控制乳胶粒大小及分布的关键阶段,由此提出了对于单体不同水溶性体系控制乳胶粒大小分布的策略,并以实验考核这些策略的合理性。     

Mechanistic study of boron trifluoride catalyzed ε‐caprolactone polymerization in the presence of glycerol

Boron trifluoride catalyzed ε‐caprolactone polymerization in the presence of glycerol can produce poly(ε‐caprolactone) with a high weight‐average molecular weight and a broad molecular weight distribution. This article reports an investigation of the polymerization mechanism to determine the formation of these molecular weight features through a study of the polymerization kinetics and the molecular structure with NMR. The polymerization proceeds via an activated monomer mechanism, resulting in polymer molecules with hydroxyl chain ends. The broad molecular weight distribution can be attributed to the etherification reactions between hydroxyl chain ends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3900–3906, 2006     

宽分子量分布高聚合度PVC的合成和性能

针对高聚合度聚氯乙烯加工性能较差的缺点，采用２段聚合温度法合成了宽分子量分布的ＰＶＣ树脂，并对树脂的热稳定性、加工性能和力学性能进行了研究。