The temperature dependence of the doolittle equation parameter for polymer liquids

The Doolittle equation parameter for polymer liquids is a function of temperature. Its dependence on temperature can be expressed by a quadratic equation. The constants in the equation are determined for four vinyl-type polymer liquids: polystyrene (PS), poly(vinyl acetate) (PVAc), polydimethylsiloxane (PDMS), and polyisobutylene (PIB). It was found that the Doolittle parameter decreases with increasing temperature. Equations are presented for the pressure and temperature coefficients of viscosity, isoviscous temperature coefficient of volume, and the constant K_m in the Miller equation. Comparisons of the predictions of the equations, with those in the literature, are favorable. © 1993 John Wiley & Sons, Inc.     

A new thermodynamic function for phase‐splitting at constant temperature,moles, and volume

We introduce a new thermodynamic function for phase‐split computations at constant temperature, moles, and volume. The new volume function F_i introduced in this work is a natural choice under these conditions. Phase equilibrium conditions in terms of the volume functions are derived using the Helmholtz free energy. We present a numerical algorithm to investigate two‐phase equilibrium based on the fixed point iteration and Newton method. We demonstrate usefulness and powerful features of the new thermodynamic function for a number of examples in two‐phase equilibrium calculations. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Synthesis and electrochemical characterization of PEO-based polymer electrolytes with room temperature ionic liquids

New gel polymer electrolytes containing 1-butyl-4-methylpyridinium bis(trifluoromethanesulfonyl)imide (BMPyTFSI) ionic liquid are prepared by solution casting method. Thermal and electrochemical properties have been determined for these gel polymer electrolytes. The addition of BMPyTFSI to the P(EO)₂₀LiTFSI electrolyte results in an increase of the ionic conductivity, and at high BMPyTFSI concentration (BMPy⁺/Li⁺ = 1.0), the ionic conductivity reaches the value of 6.9 × 10⁻⁴ S/cm at 40 °C. The lithium ion transference numbers obtained from polarization measurements at 40 °C were found to decrease as the amount of BMPyTFSI increased. However, the lithium ionic conductivity increased with the content of BMPyTFSI. The electrochemical stability and interfacial stability for these gel polymer electrolytes were significantly improved due to the incorporation of BMPyTFSI.     

Crystallization and relaxation dynamics of glass-forming liquids at the Kauzmann temperature

If the entropy extrapolation of supercooled liquids (SCL) suggested by Kauzmann was correct, then they would have the same entropy as their stable crystalline phase at a certain low temperature, below the laboratory glass transition (T_g), known as the Kauzmann temperature (T_K). Extrapolating even further, the liquid entropy would be null at a temperature above absolute zero, violating the Third Law of Thermodynamics and constituting a paradox. Several possibilities have been proposed over the past 70 years to solve this paradox with different degrees of success. Our objective here is to access liquid dynamics at deep supercoolings to test the so-called crystallization solution to the paradox. By comparing the relaxation and crystallization kinetics determined above T_g and extrapolated down to T_K, a possible solution would be that the crystallization time is shorter than the relaxation time, which would mean that a SCL cannot reach the T_K. In this case, the liquid stability limit or kinetic spinodal temperature (T_ks) should be higher than T_K. We tested two fragile glass-forming liquids (diopside and wollastonite) and two strong liquids (silica and germania). For the fragile substances, T_ks ? T_K, hence such a supercooled liquid cannot exist at T_K, and the entropy crisis is averted. On the other hand, the results for the strong liquids were inconclusive. We hope the findings of this work encourage researchers to further investigate the liquid dynamics of different strong glass-forming systems at deep supercoolings.     

Surface tension of polymer liquids

A cell theory for the prediction of the surface tension of simple liquids is adapted to polymer liquids. The combinatory, free volume and potential energy zero terms of the partition function are all modified to account for the preservation of connectivity when a surface is created. Theory and experiment are in good agreement without an adjustable surface parameter.     

Microstructure of room temperature ionic liquids at stepped graphite electrodes

Molecular dynamics simulations of room temperature ionic liquid (RTIL) [emim][TFSI] at stepped graphite electrodes were performed to investigate the influence of the thickness of the electrode surface step on the microstructure of interfacial RTILs. A strong correlation was observed between the interfacial RTIL structure and the step thickness in electrode surface as well as the ion size. Specifically, when the step thickness is commensurate with ion size, the interfacial layering of cation/anion is more evident; whereas, the layering tends to be less defined when the step thickness is close to the half of ion size. Furthermore, two‐dimensional microstructure of ion layers exhibits different patterns and alignments of counterion/co‐ion lattice at neutral and charged electrodes. As the cation/anion layering could impose considerable effects on ion diffusion, the detailed information of interfacial RTILs at stepped graphite presented here would help to understand the molecular mechanism of RTIL‐electrode interfaces in supercapacitors. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3022–3028, 2015     

Accurate measurement of creep of nylon-6,6 at constant temperature and humidity

This paper describes a purpose-built environmental chamber housing three creep machines for accurate measurements of creep in a hygroscopic polymer. The environmental chamber controls the temperature to within ±0.1°C and the relative humidity to within ±1% r.h. or better. The creep machines are sufficiently accurate to limit the error in the measured modulus to ±0.4% at the 0.1% strain level. Also described are new designs of lateral extensometers and of a simplified zero-load control machine based on similar principles to those of the creep machines, but which can also be adapted for accurate creep tests on very small test pieces using loads of as little as 1 N. Creep results are presented of nylon-6,6 at several constant stresses and relative humidities at 23.5°C, each test lasting for six weeks. Evidence is given, in the form of 24 h creep curves, of an aging phenomenon in nylon-6,6: a progressive increase in stiffness with storage time at the test condition following humidification at 90% r.h.     

Specific volume of molten thermoplastic polymer composite at high pressure

The specific volume of thermoplastic polymers and composites with glass fiber have been measured at high pressure, up to 2000 kg/cm², in the molten state by a dilatometer. The specific volume and thermal expansion coefficient of the melts increase with increasing temperature at a constant pressure at a constant temperature. The data of specific volume of molten polymers were satisfactorily fitted to an empirical equation of state based on the Tait equation. Furthermore, it is found that the data of specific volume of molten composites were suitably fitted by an additive rule of Tait equation from the volume fractions of specific volume of polymers and the glass fiber in composites. The thermal expansion coefficients of molten polymers and composites are approach to the derivative values of the Tait equation, and the additive Tait equation, respectively.     

Equation of state for polymer liquids

An empirical pressure–volume–temperature (PVT) equation of state is presented for polymers in the liquid state, i.e., above the melting point of a crystalline polymer or the glass transition of an amorphous polymer. In terms of reduced variables, the equation is given by \documentclass{article}\pagestyle{empty}\begin{document}$\overline {PV^5 } = \overline {T^{{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}} } - \ln {\rm }\overline V $\end{document}. Values of the three reducing parameters are given for 23 polymers. Comparison of the predictions of this equation with experimental data are made for all of the polymers. The data are generally available up to a pressure of 2 kbar and a temperature 100°C above the melting or glass transition temperature. Measured and calculated volumes agree within about 0.001 cm³/g, which is the accuracy of the measurements. Detailed comparisons with the empirical Tait equation are made. Equations are also presented for isothermal bulk modulus, thermal expansion coefficient, and Gruneisen parameter.     

室温离子液体室

介绍了主要由烷基咪唑盐阳离子及氟阴离子组成的室温离子液体的制备、物理性质、化学性质及其在常温条件下的应用.     

蓖麻油质量定压热容与温度的关系

采用电热丝直接浸入液相加热、三层保温的量热装置，利用已知质量定压热容的甘油校正了蓖麻油质量定压热容测定过程中不同温区的热损失，据此测定了蓖麻油在310K～410K温区的质量定压热容。     

Surface tension and surface entropy for polymer liquids

A cell theory for the prediction of the surface tension of polymer liquids is modified to include an entropic effect due to molecular asymmetry. Also considered is the extent of the effect of the preservation of connectivity in the vicinity of the surface upon the potential energy zero term due to missing nearest neighbors of orders greater than one. Theory and experiment are in good agreement without an adjustable surface parameter.     

Chemical reactions of polymer crosslinking and post-crosslinking at room and medium temperature

This review focuses on various strategies that enable the crosslinking and post-crosslinking of polymers, excluding crosslinking obtained by radiation (e.g., X-ray, UV, etc.) and that at high temperature. The review is divided into two main parts: systems enabling crosslinking at room temperature and those for which crosslinking occurs at intermediate temperatures (<150 °C). In the first part, various key functional groups can be used, such as (i) carboxylic acid involving reactions with compounds that bear carbodiimide or aziridine functions; (ii) acetoacetyl groups (with isocyanate, activated alkenes, aldehyde, amine functions); (iii) reactions involving activated amines with carbonyl functions (aldehydes, ketones, etc.); (iv) species bearing acetals as pH-sensitive crosslinking agents since they are stable in basic medium but they can self react under acidic conditions; (v) acrylamide functions which are able to self-crosslink; (vi) crosslinking agents able to react with water (such as species that bear a poly(alkoxy)silane for sol-gel process) and derivatives containing isocyanate functions and (vii) systems that require oxygen, for example polymers bearing double bonds, boranes for generating hydroperoxides and acetylenic functions which undergo acetylenic coupling. The second series of systems, used at higher temperatures (yet below 150 °C) involving the following key functions: (i) carboxylic acid that react with oxazoline, or epoxide function where specific catalysts are necessary; (ii) alcohols reacting with protected urethanes, azlactones and methylol amide (for coating applications); (iii) azetidines (obtained from a cyclic amine onto an activated double bond) which self-crosslink; (iv) reversible Diels-Alder reaction (such as furane/bismaleimide reaction), and (v) Huisgen reactions between azido and triple bond.Various examples are presented, along with a discussion of their properties and applications.     

Prediction of creep of nylon-6,6 at constant stress,temperature and moisture content

A method is described of accurately superposing creep curves, obtained at different relative humidities, that each covered six decades of time. The superposition required an empirical distortion of the logarithmic-time scale; for which the justification was that it not only gave more accurate superposition, but also that the same distortion could be successfully used for five relative humidities and three stresses and needed the same horizontal shift factor for all stresses except at the highest relative humidity, of 90%. Equations were fitted to the resulting master curves and non-linearity correction factors, enabling the computer to predict creep curves at any constant stress up to 12 MN/m² and at any constant humidity up to 90% r.h. No attempt has been made to explain the success of the distortion used, but its usefulness is readily apparent.     

连续式高效节能梯级恒温浮选加药装置关键技术研究

运用自适应神经模糊控制原理,在参考传统浮选加药恒温设备的基础上,设计出了一款适应性更强、精度更高、方便灵活、移动式的高效节能梯级恒温浮选加药装置,该装置不用上位机电脑,能自动连续混加药,加热速度快,恒温效果好,加药过程药剂定常流动,操作人性化,运行成本低,还可以节约能源,提高浮选指标.     

Bubble formation in quiescent liquids under constant flow conditions

In this investigation, a simple equation has been theoretically developed to predict the bubble detachment diameter in quiescent liquids under constant volumetric gas flow conditions. The equation is valid in the bubbling regime up to transition to the jetting regime and for liquids with very low up to very high viscosities. Known experimental measurements were used to examine the validity of the developed equation. The present measurements cover gas Weber numbers from about 0 up to 4, liquid dynamic viscosities from 10⁻³ up to 1 Pa s, and nozzle diameters from 0.2 up to 6 mm. The comparison between the theoretical predictions and the experimental measurements is satisfactory; the deviations lie in most cases within ± 10%.     

Bubble formation in viscous liquids under constant flow conditions

Bubble formation from single nozzles has been studied in liquids of different viscosities. The viscosity is varied in the range 50 to 500 c.p., whereas flow rates up to 100 cm³/second have been investigated. A model based on a two step (viz. expansion and detachment) mechanism has been proposed for bubble formation. The model explains the results of the present investigation as well as those reported in the literature for similar systems. As an extreme case, the model is tested on liquids of very low viscosity after dropping the viscosity terms from the equations and is found to explain even these data quite well.     

Huggins' constant and unperturbed parameter of dilute polymer solutions

A novel method developed to evaluate the unperturbed parameter K_θ from the viscometric data of dilute polymer solutions can be considerably simplified by making the reasonable assumption that the Huggins' constant under theta conditions, k_Hθ, is equal to ½ for a number-average degree of polymerization of over about 2000. Two linear equations are derived pertaining to the present analysis, one to deal with the experimental data, and the other specially to estimate the intrinsic viscosity [η]θ which corresponds to κ_Hθ. All calculations were done by the linear least-squares method. The K_θ was computed by the Mark–Houwink–Sakurada equation. It is shown that reliable results on K_θ can be obtained for polystyrene and poly(vinyl acetate).     

Comparison of mesoscopic solvation pressure at constant density and at constant chemical potential

The solvation pressures arising from the confinement of a fluid by surfaces are calculated under two different thermodynamic conditions, namely at constant density and at constant chemical potential, through mesoscopic scale simulations. We consider two types of fluids, a model monomeric solvent on the one hand, and a fluid composed of linear polymers dissolved in a monomeric solvent, on the other. For these systems our simulations show that the prediction of the solvation (or disjoining) pressure when the chemical potential is kept fixed is different from that obtained when the total density is fixed. We find however, that the same trend between both types of simulations can be obtained when the value of the fixed density is chosen as the average value of the density obtained at constant chemical potential.     

恒温低能量乳化法制备水包油纳米乳液及其稳定性研究

25℃下用恒温低能量乳化法在水/复配壬基酚聚氧乙烯醚/生物柴油的系统中,制备了稳定的水包油纳米乳液.通过体系的相行为研究得到了纳米乳液的形成条件;用动态光散射(DLS)与透射电镜(TEM)测试纳米乳液的颗粒形貌、粒径大小及分布;并通过DLS测试纳米乳颗粒粒径随时间的变化,探索了纳米乳不稳定机制.结果表明:纳米乳液是通过双连续微乳液稀释得到,颗粒粒径主要被双连续相结构所控制,而与乳液中最终水的质量分数无关;纳米乳液体系的颗粒为球形,多分散系数小于0.2,粒径分布主要在20 nm～35 nm;纳米乳液不稳定机制符合絮凝作用.