基于自组织的两亲聚合物驱油剂的渗流特性研究

针对大庆油田所应用的两亲聚合物,利用化学驱模拟评价装置研究了其渗流特性,得出了其在多孔介质中的渗流规律以及部分影响因素。结果表明,同浓度的两亲聚合物比HPAM的阻力系数和残余阻力系数更大;两亲聚合物比HPAM具有更大的粘弹性,具有更强的抗剪切性,并且在多孔介质中流动存在胀流性的行为;两亲聚合物的浓度越高,阻力系数和残余阻力系数越高;粘度随着老化时间的增长先增加后减小,在增加阶段,老化时间越长,阻力系数和残余阻力系数越大;岩心的渗透率越小,残余阻力系数越大。     

The dynamic behavior and stress relaxation of polymer melts

Polymer melts exhibit a decrease in apparent viscosity as a function of decreasing time scale of shearing. In order to obtain an understanding of the mechanisms giving rise to this non-Newtonian behavior studies have been made of the dynamic linear viscoelastic response, the limit of linear viscoelastic behavior and the stress relaxation in polymer melts after steady state shearing. The results of these experiments are analyzed with respect to shear induced changes in the relaxation spectrum and the effect of these changes on the apparent viscosity.     

Extruded foams from microbial poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and its blends with cellulose acetate butyrate

Extrusion foaming of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) and two blends of PHBV with cellulose acetate butyrate (CAB) were studied using an azodicarbonamide (AZ) blowing agent and a single‐screw extruder. The concentration of the blowing agent was systematically varied from 0 to 4.0 phr to achieve maximum density reduction reaching 41%, as well as to obtain information on the dependence of cell growth on blowing agent concentration. Extruded foams were characterized in terms of their bulk densities and cellular morphologies. Stereological and statistical methods permitted full characterization of the three‐dimensional cell size distributions, assessing the average cell diameters (ranging from 58 to 290 μm) and cell densities (ranging from 650 to 180,000 cm^?3). The variation in cellular morphology among foams consisting of different polymer matrix or blowing agent concentration was compared. The results were analyzed by considering the influence of viscoelastic properties of the polymer matrix on the bubble growth during foaming. Significantly higher melt viscosity and elasticity and reduced gas solubility of the PHBV/CAB blends are believed to retard cell coalescence and collapse during foam expansion, resulting in more uniform cell size distribution and better homogeneity of cellular morphology. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

RHEOLOGICAL AND MIST IGNITION PROPERTIES OF DILUTE POLYMER SOLUTIONS

A spinning disc atomizer has been used to characterize the mist flammability of Jet A and diesel fuels that contain high molecular weight polymers. The critical disc velocity required to produce significant flame propagation was shown to depend on polymer concentration, molecular weight, solvent viscosity, and polymer degradation.

The viscoelastic properties of these same polymer solutions have been characterized by a maximum Darcy viscosity measured from flow in packed tubes. For the polymers discussed in this paper, the maximum Darcy viscosity was independent of the bead size or tube length; however, it was strongly affected by the same variables that affected mist flammability; i.e., polymer concentration, molecular weight, solvent viscosity, and polymer degradation.

The critical ignition velocity of dilute polymer solutions is shown to depend on the Darcy viscosity in a similar manner as observed for viscous oils. At low viscosities, the ignition velocity is only slightly affected, but the dependence grows stronger as the viscosity (both shear and Darcy) increases. A close correspondence was also shown to exist between the ignition velocity of a polymer solution with a high Darcy viscosity and the ignition velocity of a Newtonian oil with approximately the same high shear viscosity.

Numerous similarities are described between flow-induced birefringence of dilute polymer solutions with opposed capillary jets and viscoelastic resistance of dilute polymer solutions in packed tubes. These similarities suggest that the maximum Darcy viscosity is associated with a condition of almost complete extension and alignment of the polymer molecules.     

Flow of a FENE Fluid in Packed Beds or Porous Media

An analysis describing viscoelastic flow of a FENE fluid in packed beds or porous media is presented based on the capillary hybrid model of the flow. A close similarity is revealed between the functional relationship of the reduced elongational viscosity to and that relating the reduced mean elongational viscosity λ_H ? to the Deborah number which is utilized in the flow expressions. The agreement obtained between the predicted and experimentally determined evaluations of the resistance factor, including the effects of variation of polymer concentration, molecular weight and solvent quality was found to be satisfactory. Onset Reynolds numbers for enhanced flow resistance are also predicted successfully.     

Influence of chemical polymerization conditions on the properties of polyaniline

The chemical polymerization of aniline in aqueous solutions was studied as a function of a wide variety of synthesis parameters, such as pH, relative concentration of reactants, polymerization temperature and time, etc. The polymer was synthesized using a number of different oxidizing agents and different protonic acids. It was found that the reaction yield was not sensitive to most variables. By contrast, the inherent viscosity of the polymer, measured in solutions in concentrated sulphuric acid, was strongly dependent on the synthesis parameters. Optimum reaction conditions are outlined for the chemical polymerization of aniline, for post-treatment with aqueous HCl solutions, and for compensation of the emeraldine salt into its base form. Under such conditions, high-quality polyaniline base was synthesized with an inherent viscosity (0.1% w/w polymer in sulphuric acid) as high as 2.32 dl g⁻¹.     

Influence of polyethylene oxide on absorption of carbon dioxide into aqueous <Emphasis Type="Italic">N</Emphasis>-methyldiethanolamine solution

Carbon dioxide was absorbed into aqueous polyethylene oxide (PEO) solution containing N-methyldiethanolamine (MDEA) in a flat-stirred vessel to investigate the effect of non-Newtonian rheological behavior of PEO on the chemical absorption rate of CO₂, where the reaction between CO₂ and MDEA was assumed to be a first-order reaction with respect to the concentration of CO₂ and MDEA, respectively. A unified correlation equation containing the Deborah number, which reflects the viscoelastic properties of a non-Newtonian liquid, was used to obtain the volumetric liquid-side mass transfer coefficient of carbon dioxide in aqueous PEO solution. The elastic properties of PEO accelerated the absorption rate of CO₂ compared with that of a Newtonian liquid based on the same values of viscosity.     

适用于丙烯二聚反应非均相催化剂的研究进展

丙烯二聚反应是生产4-甲基-1-戊烯、1-己烯等端碳烯烃的重要手段,其产物可作为特种高分子材料单体、汽油添加剂和化工有机中间体,关键技术在于高效催化剂的开发。非均相催化剂相比于均相催化剂因易回收、对环境污染小等优点受到了学者们的广泛关注。本文综述了丙烯二聚非均相催化剂的研究进展,依据固体碱催化剂与固体酸催化剂在丙烯二聚反应中不同的反应机理,比较了两者各自的优缺点。回顾了固体碱催化剂的发展历程及工业化应用,并以碱金属钾为例总结了反应机理。详细介绍了固体酸催化剂中的固体磷酸催化剂、分子筛催化剂和负载型过渡金属催化剂。针对固体碱催化剂制备条件苛刻等问题,提出了改善催化装置的新思路;针对固体酸催化剂选择性不足的劣势,指出了应该进一步完善机理,并合理设计酸性载体与过渡金属相结合的催化剂。     

一种加快海上油田聚合物溶解速度的方法探讨

为了解决目前渤海油田聚合物溶解时间过长而无法满足配注量要求的问题,将研磨机引入海上油田三次采油领域,提出了胶体研磨加快聚合物干粉溶解速度的方法。通过改变研磨级数和研磨浓度,测得不同条件下的聚合物溶液母液和目标液的粘度,通过对比得出了不同研磨条件下研磨机对母液和目标液粘度大小与变化趋势的影响。实验结果表明,胶体研磨可以加快聚合物干粉的溶解,从母液粘度变化来看,能缩短溶解时间30 min左右;不同研磨级数条件下,研磨后形成的母液和对应的目标液粘度与常规不研磨相比损失要大;研磨浓度为10 000~30 000 mg/L所得到溶液粘度值比研磨浓度为5 000 mg/L要大,可作为研磨的优选参数。     

Time–temperature–transformation diagram for reactive processing of polyamide 12

In order to describe the different events occurring during the anionic polymerization of polyamide 12 (PA12), a general concept of a time, temperature, and transformation (TTT) diagram was established and related to reactive processing conditions. Polymerization kinetics were established, and it was found that the reaction was best described by an autocatalytic expression. Polymerization temperatures above and below the final polymer melting temperature were considered. Furthermore, the variation of the melting temperature and viscosity were followed as a function of the polymerization time and degree of conversion. It was shown that monomer–polymer phase separation and crystallization may occur during PA12 polymerization. The results could be adapted for use during liquid molding of PA12 polymers and their composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 963–972, 2001     

Investigation into Reactions of Starch with Monochlorotriazinyl-β-Cyclodextrin and Application of their Products in Textile Sizing

This article presents a study on the chemical modification of starch and hydrolyzed starches through their reactions with reactive cyclodextrin (RCD). Monochlorotriazinyl-β-cyclodextrin was investigated under a variety of conditions. The results obtained signify that the reaction was favored in an alkaline media rather than an acidic media, and in shorter rather than larger liquor ratios. Maximization of the reaction could also be achieved at 40°C for 60 min. Of the several alkaline catalysts used, NaOH proved to be the best when used at a concentration of 10 g/l. The reaction of starch and hydrolyzed starches with RCD was determined using a concentration of the latter. The apparent viscosity of the resulting polymeric products depends upon both the extent of reaction, expressed as a nitrogen percentage, and the degree of acid hydrolysis prior to the modification. Evidence for involvement of starch and RCD via chemical bonding was obtained through FT-IR analysis. Furthermore, the newly synthesized starch-based polymeric products were applied to a light cotton fabric and further evaluation of the sized materials was conducted by monitoring the size add-on, size removal, and strength properties of the fabric was conducted.     

聚合物熔体动态黏弹特性微尺度效应实验研究

针对聚合物熔体在微流道内,因拉伸/压缩作用导致的黏弹特性受物理尺度影响的问题,通过动态剪切流动实验系统研究了四种聚合物材料的黏弹特性,以及黏弹特性随物理尺度的变化规律。结果表明,在角频率1~100 rad/s的范围内,聚酰胺、聚氨酯、聚乳酸均表现出耗能模量大于储能模量的黏性占优特征,聚丙烯在高频区时表现出弹性占优特征。储能模量与耗能模量均随着物理特征尺度的减小而降低。物理特征尺度从1000 μm减小到250 μm的变化过程中,聚氨酯、聚酰胺和聚丙烯三种熔体的弹性效应对微尺度变化的敏感性比黏性效应强烈,储能模量变化率与耗能模量变化率的差值分别为5.8%、4.2%和2.6%。聚乳酸熔体的黏性效应对微尺度变化的敏感性与弹性效应基本一致,其储能模量变化率与耗能模量变化率的差值为-0.3%。材料分子链特征的差异导致储能模量与耗能模量随物理特征尺度减小的变化率不同。熔体黏弹特性对微尺度变化敏感性的强弱依次为聚氨酯、聚酰胺、聚丙烯和聚乳酸,其黏弹性特征参量的变化率分别为28.6%、22.6%、20.6%和19.45%。     

A macromolecular deformation model to estimate viscoelastic flow effects in polymer melts

The elastic deformation of polymer macromolecules in a shear field is used as the basis for quantitative predictions of viscoelastic flow effects in a polymer melt. Non-Newtonian viscosity, capillary end correction factor, maximum die swell, and die swell profile of a polymer melt are predicted by the model. All these effects can be reduced to generic master curves, which are independent of polymer type. Macromolecular deformation also influences the brittle failure strength of a processed polymer glass. The model gives simple and accurate estimates of practically important processing effects, and uses fitting parameters with the clear physical identity of viscoelastic constants, which follow well established trends with respect to changes in polymer composition or processing conditions.     

Relationship between interfacial phenomena and viscoelastic behavior of laminated materials

A literature review shows that the main arguments used to describe viscoelastic behavior of polymer composites are the existence of an interphase and/or physico-chemical matrix-reinforcement interactions. The purpose of this investigation was to study the influence of both of these parameters on the viscoelastic behavior of a sandwich structure. Using a theoretical approach of the mechanical coupling between phases in laminate composites, the interphase influence is shown to be negligible. In order to understand the influence of an interphase on viscoelastic features of laminates, some metal/polymer/metal laminates were processed under various conditions to obtain different degrees of metal/polymer adhesion. Dynamic mechanical spectroscopy tests reveal that both the amplitude of the main loss factor peak and the low temperature apparent modulus increase with the adhesion. Finite elements calculations show that discontinuities of displacements at the metal/polymer interface explain the loss peak changes. The continuity of displacements is ensured only from a threshold value of the peel energy.     

Viscoelastic properties and structure of poly(acrylonitrile‐co‐methacrylic acid) polymer solutions for gel spinning at long aging times

The objective of the research is to obtain a more complete understanding of how aging affects the viscoelastic properties of polymer solutions to be used as starting materials for gel spinning of polymer fibers. Specifically, poly(acrylonitrile‐co‐methacrylic acid) solutions were prepared and characterized using rheological measurements and nuclear magnetic resonance spectroscopy. The results indicate that elastic character increased with increasing polymer concentration and that gelation of these solutions continued up to aging times of several weeks. Additionally, comparing the results from the two characterization methods show that while gelation continues to occur, the viscoelastic properties decrease after a critical time point suggesting that a chemical change occurs in the solutions at long times. However, these changes impact the solution dynamics minimally as the effective network properties were similar at the aging times studied here, but considerations for long‐term storage of polymer solutions for gel spinning are warranted. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39821.     

Transesterification of neat and used frying oil: Optimization for biodiesel production

In this study, the characteristics and performance of three commonly used catalysts used for alkaline-catalyzed transesterification i.e. sodium hydroxide, potassium hydroxide and sodium methoxide, were evaluated using edible Canola oil and used frying oil. The fuel properties of biodiesel produced from these catalysts, such as ester content, kinematic viscosity and acid value, were measured and compared. With intermediate catalytic activity and a much lower cost sodium hydroxide was found to be more superior than the other two catalysts. The process variables that influence the transesterification of triglycerides, such as catalyst concentration, molar ratio of methanol to raw oil, reaction time, reaction temperature, and free fatty acids content of raw oil in the reaction system, were investigated and optimized. This paper also studied the influence of the physical and chemical properties of the feedstock oils on the alkaline-catalyzed transesterification process and determined the optimal transesterification reaction conditions that produce the maximum ester content and yield.     

Influence of shearing history on the rheological properties and processability of branched polymers. III. An amorphous long-chain branched polymer

Viscoelastic properties of branched polymers vary with their shearing history; notwithstanding, their primary molecular parameters do not change. According to a recent study, such viscoelastic variation was believed to be observed only with crystalline long-chain branched polymers such as low-density polyethylene or polyacetal. That is, the origin of the viscoelastic variation was attributed to the presence of specific entanglements at the branching points, which was formed during the crystallization process. However, the viscoelastic variation of the long-chain branched polymers is the phenomenon at temperatures well above their melting points, namely, it is considered that whether the long-chain branched polymers are crystalline or not is not essential for the occurrence of the viscoelastic variation. Thus, the influence of the shearing history on the rheological properties of an amorphous long-chain branched polymer was investigated in this paper, and it was found that, irrespective of their crystallinity, the viscoelastic properties of long-chain branched polymers vary according to their shearing history.     

Monitoring of photopolymerization kinetics and network formation by combined real-time near-infrared spectroscopy and ultrasonic reflectometry

For in situ monitoring of fast changes of shear modulus and chemical conversion during UV radiation curing an ultrasonic (US) reflection method was combined with real-time near infrared (NIR) spectroscopy. The combined setup has been applied to study photopolymerization of different resins as acrylates, epoxy acrylates, acrylated polyurethanes and cationic epoxy resins in order to achieve a deeper understanding of the interdependence of reaction kinetics and changes of mechanical/rheological properties. The simultaneously recorded conversion–time and modulus–time curves allow differentiating between mass and diffusion controlled polymerization regime. Light curing and dark curing phases are indicated by two distinct regions in the conversion–time curves. By rescaling the curing time by chemical conversion modulus–conversion curves were constructed, which are described by combining a viscoelastic relaxation model with the conversion dependence of relaxation times. The NIR-US setup was used to study the influence of chemical composition and curing conditions on the polymer network formation.     

Rheology of miscible polymer blends with viscoelastic asymmetry and concentration fluctuation

How the viscoelastic asymmetry affects the concentration fluctuation and its manifestation in rheology of miscible polymer blends are examined in this work. The linear viscoelastic stress of polymer blends is divided into the components stress and the stress due to concentration fluctuation. The dynamic coupling between the fluctuation in concentration and the stress is represented by the two-fluid model, which is linearized and solved under small amplitude oscillatory shear to give the concentration fluctuation induced stress. A strong influence of components’ viscoelasticity on the concentration fluctuation is clearly demonstrated in the viscoelastic asymmetric system through the enhancement in the elastic modulus at low frequency. The decisive parameter is the viscoelastic length which depends mainly on the dynamic asymmetric parameter and the zero shear viscosity of blends. It is also found that the dynamic coupling effect gradually fades as it gets close to the spinodal point, where pure concentration fluctuation dominates. The dynamic moduli due to the concentration fluctuation at spinodal point exhibits the same power law dependence on oscillatory frequency, which is a characteristic of critical gel and could be used as an alternative criteria to determine the spinodal temperature.     

过渡金属Mn取代多金属氧簇催化醇解废旧PET

合成了一种具有三明治结构的过渡金属Mn取代的多金属氧簇(POMs)催化剂Na12[WZnMn2(H2O)2(ZnW9O34)2],用于催化聚对苯二甲酸乙二醇酯(PET)的醇解过程,对反应温度、反应时间和催化剂量等实验条件进行了优化。结果表明,在催化剂量为PET质量的1.0%、质量比PET/EG(乙二醇)为1:4及190℃的条件下反应80 min,PET降解率可达100%,对苯二甲酸乙二醇酯(BHET)的收率达84.42%。