Tension behaviour of HNBR and FKM elastomers for a wide range of temperatures

This article presents uniaxial tension tests of three different elastomer compounds commonly applied as seal materials in the oil and gas industry. The tests were performed at five different temperatures, ranging from −20 to 150 °C. Optical measurements were used to ensure high quality stress–strain data. The material samples were exposed to a cyclic deformation history, enabling the viscoelastic behaviour to be explored. A considerable effect of temperature changes was found, with a pronounced increase of stiffness and viscosity for the lowest temperatures. A dip in the stress–strain curve was seen for one of the hydrogenated nitrile butadiene rubbers tested at low temperatures. Matrix-particle debonding simulations qualitatively described this stress dip. For the tests performed at the highest temperatures, a considerable number encountered material failure.     

Performance limits and kinetic optimization of parallel and serially connected multi-column systems spanning a wide range of efficiencies for liquid chromatography

Using a set of experimentally determined liquid chromatography column performance data, it has been investigated how a range of efficiencies can best be covered when using a multi-column system. Two main variants are considered: a serially-connected variant (realizing different column lengths by connecting a different number of column segments in series) and a parallel-connected variant (realizing different column lengths by simply switching between columns with a different length arranged in parallel). Both variants are compared for their ability to keep the average analysis time along a given range of efficiencies as close as possible to the intrinsic Knox & Saleem-speed limit. It was found that the serial connection mode offers a better compromise between average speed and amount of required silica (total required column length) than the parallel connection mode for all efficiency ranges running from 5000–10,000 plates up to 75,000–150,000 plates. Considering an ultra-high performance liquid chromatography (UHPLC) operation at 1200 bar, the best possible serial connection system can get within about within 15–25% of the Knox & Saleem-speed limit, whereas a three-column parallel system can only get to within 40–50% of the speed limit, while needing 50–100% more total column length. In absolute terms, the serially-connected system with individually optimized segment lengths should be able to cover a range of 5000–75,000 theoretical plates (dynamic range of 25) in an average analysis time of 14.3 min when using a 1200 bar instrument. At 400 bar, this would be 37.9 min, showing that the construction of wide-efficiency range systems would be one of the application areas where the advantages of UHPLC-conditions would be most fully realized.     

Correlation of viscosities of pure liquids in a wide temperature range

On the basis of Eyring's absolute rate theory, a new two-parameter model is presented for correlating the viscosity data of pure saturated liquids in a wide temperate range. The correlation relates the viscosity, a non-equilibrium property, to equilibrium properties. The parameters in the new correlation can be easily determined through a few viscosity data and a knowledge of the vapor pressure, the saturated liquid volume and the heat of vaporization. The viscosities of 106 pure compounds, including polar, nonpolar, organic and inorganic liquids with total 1473 data points are correlated using this model and compared with data reported in the literature, and the overall average deviation is 1.51%. The results show that the correlation with the new model is satisfactory.     

Morphological origins of temperature and rate dependent mechanical properties of model soft thermoplastic elastomers

Thermoplastic elastomers (TPEs) combine high elasticity with melt processability due to their structural features being based on physical associations rather than chemical crosslinking. Their mechanical properties are governed by the interplay of the different dynamics present in the system (i.e., hard block associations and soft block mobility) combined with their morphology. Irrespective of their exact chemical structure or type of association (crystals, hydrogen bonds, or glassy domains), many soft TPEs show a reduction in toughness at elevated temperatures. In this study, we investigate the high-temperature mechanical properties of a model series of industrially relevant TPEs via systematically varying composition and molecular weight. The results show an increase in temperature resistance and in large-strain stress response as chain length increases. We underline the key parameters that influence the mechanical behavior and explain the observed effect of molecular weight on both the temperature- and rate-dependent large-strain response. A physical network-based model is presented that can explain the experimental findings assuming an improved network connectivity and extended lifetime of the entangled segments with increasing molecular weight.     

Non-phthalate plasticizer from camphor for flexible PVC with a wide range of available temperature

A bio-based plasticizer, (1′,7′,7′-trimethyldispiro [ [1,3]dioxolane-2,2′-bicyclo [2.2.1]heptane-3′,2″- [1,3]dioxolane]-4,4″-diyl)bis (methylene) dioctanoate (abbreviated as CDO), was designed to replace a traditional phthalate-based plasticizer. The structure of CDO was analyzed by ¹H NMR. The characteristics of CDO plasticizers, which were judged to have excellent compatibility with PVC due to their solubility parameters, were evaluated by thermal and mechanical analyses and compared with dioctylphthalate (DOP). PVC with 20% CDO added was thermally stable up to 251.9 °C and exhibited excellent strength and flexibility with a high T_g derived from its robust and bulky structure. In addition, since CDO is intertwined with the polymer chain, it shows excellent migration properties in many solvents. The results of our study suggest that CDO can be applied to produce flexible PVC and to expand PVC coverage due to the improved migration resistance.     

宽广温度范围的水离子积计算公式

宽广温度范围的水离子积是在理论上和实际应用上涉及面很广的重要物理化学性质之一.傅培鑫,Quist及Marshall等在总结实验数据的基础上提出了相应的计算水离子积的经验公式;Taylor还用热力学方法进行了计算.在饱和蒸气压及0～800℃范围内,以Marshall-Franck的经验公式准确度为最高,并由国际蒸气性质协会(IAPA)于1980年公布为计算宽广温度范围的水离子积公式.但是在温度较高(200～300℃)时,此公式的计算值与实验值之间的误差随温度升高而逐渐增大,平均误差为0.033pK_w单位.     

Thermodynamic quantities for the acid dissociation of alkylammonium ions in water over a wide temperature range

Enthalpies of protonation in aqueous solution have been determined from calorimetric measurements between 0 and 100°C for methylpentylamine, butyldimethylamine, and quinuclidine; between 0 and 125°C for di-iso-propylamine; and between 0 and 75°C for 1-azacycloheptane. Values ofpK_a at 25°C have been determined from pH measurements using a glass electrode for di-iso-propyl-, methylpentyl-, and butyldimethylamine. The calorimetric results are used together with values ofpK_a at 25°C to derive expressions which allow the calculation of accuratepK_a values over a large temperature range. The heat capacity and entropy changes for the protonation of aqueous alkylamines found in the present and in previous studies are discussed in terms of differences in hydrophobic solvation of the alkyl groups in the neutral amines and the ions.     

A micro electron capture detector for temperature programmed analysis with capillary columns for a wide range of applications

Summary The electron capture detector (ECD) has become a indispensable and widely used tool for the detection of halogenated compounds in gas chromatography. The ECD is successfully used for routine analysis particularly in the field of environmental survey, residue determination in the food and agriculture chemistry and even more so in clinical chemistry. However, its application with high resolution glass capillary columns revealed a substantial drawback of existing ECD's, primarily the relatively large internal detector volume. The micro ECD described, with its very small cell volume (140 mm³), particularly designed for use with high resolution capillary columns, minimizes drastically the loss of separation efficiency since diffusion effects are negligible. The micro ECD permits the use of splitless or split injection techniques, as well as temperature programmed analysis to optimize sample separation. Very stable baseline and low noise conditions lower the detection limits considerably (2 pg Lindane full scale). The micro ECD can be operated either with direct current, pulsed frequency or constant current modes. Examples demonstrating the capabilities of this detector include the detection of halogenated organic volatiles in water at subnanogram levels, the determination of PCB's and pesticide residues in food as well as selected analysis in clinical chemistry, such as bile acids and amino acids in body fluids.     

A generalised perturbation-based equation of state for thermodynamic modelling of fluids over a wide range of density

A new generalized perturbed thermodynamic nonlinear isotherm regularity (GPTNLIR) equation of state (EoS) has been proposed for the fluids over the entire density range from gas to liquid. The GPTNLIR has been derived on the basis of an effective nearest neighbor pair interaction of an extended average effective pair potential (AEPP) in the framework of the thermodynamic perturbation theory (TPT). The selected AEPP is an extended Lennard-Jones (12, 6, 3) type which considers the repulsive, dispersion, dipole-dipole and longer-range interactions between pair molecules, respectively. Based on the EoS, a non-linear relationship exists between (Z– Z_CS)v² and ρ for each isotherm of fluid, where Zis the compression factor, v=1/ρis the molar volume, Z_CS is Carnahan–Starling (CS) expression for the compression factor of the reference fluid with the temperature-dependent effective hard-core diameter (σ_eff). The validity of EoS against the experimental p–v–Tdata were tested for a variety of fluids, including polar, non-polar, hydrogen bonded and quantum fluids. This EoS provides the estimation of σ_eff at T>T_c, T=T_c and T<T_c, in which T_c is critical temperature, for each real fluid using its experimental p–v–T data and the extension of TPT theory as well.     

Liquid densities of THF and excess volumes for the mixture with water in a wide temperature and pressure range

In this paper densities for THF (tetrahydrofuran) and THF + water mixtures measured with the help of the Anton Paar DMA HPM vibrating tube densimeter are reported. The pure component densities of tetrahydrofuran measured in the temperature range from 278 to 437 K and pressures up to 130 MPa were correlated with the TRIDEN-System. Additionally densities of the binary mixture tetrahydrofuran + water were measured for 6 different concentrations in a temperature range from 288 to 338 K and up to 130 MPa. Excess volumes (vE)$(v^E)$ of the mixture were determined using the own correlation of the tetrahydrofuran densities and the equation of state (EoS) for water by Wagner and Pruß. Redlich–Kister polynomials were used to fit the vE-data$v^E\text{-data}$. Additionally in this work it was checked if the vibrating tube densimeter allows the determination of the miscibility gap for the system THF–water as a function of temperature and pressure.     

Thermodynamic quantities for the solution and protonation of four C6-amines in water over a wide temperature range

The enthalpies of solution ofn-hexyl- and cyclohexylamine have been determined at temperatures up to 125°C, of di-n-propylamine up to 100°C, and of triethylamine up to 75°C from reaction-solution calorimetric experiments. Quadratic polynomials were found to give good representations of the experimental values, implying a linear variation with temperature of the heatcapacity changes. The enthalpies of protonation of the aqueous amines have been determined in the same temperature range. Linear expressions give satisfactory representations of the protonation enthalpies of the hexylamines and dipropylamine, whereas a quadratic expression is required to represent the triethylamine values. The calorimetric results are used together with reported pK _a values at 25°C to calculate the dissociation constants of the corresponding ammonium ions between 0 and 200°C. At 0°C triethylamine was found to be the weakest base, the relative base strengths being triethyln-hexyl相似文献   

Performance prediction of Co-injection self-reinforced composites parts based on temperature field

In this paper, polypropylene (PP) was used as raw material to prepare rectangular parts. The temperature change data of the reinforcement with different molding parameters during the filling process were collected by using the injection molding temperature visualization experimental analysis platform. The electronic universal mechanical testing machine (EMUTM) was used for mechanical testing, and the micro-morphology of co-injection self-reinforced composites(CI-SRCs) parts and conventional parts with different temperature fields was observed and analyzed by Polarizing microscope (PLM) and Wide angle X-ray diffraction (WAXD), and the dimensionless equations among four variables (including molding parameters, area ratio of critical temperature field, area ratio of skin layer and mechanical properties) were established. From the results, it was found that the tensile properties of CI-SRCs parts with different molding parameters are superior to that of conventional parts, with a maximum increase of 18.64%. The overall performance of CI-SRCs parts is positively correlated with the performance of the reinforcement, and the performance of reinforcement is mainly determined by the area ratio of skin layer. The difference in the micromorphology characteristics of the parts depends on the change in the temperature field. Therefore, through microscope observation and simulation software analysis, it was obtained that the theoretical critical temperature field forming the orientation skin of the parts was 154.88 °C, and the temperature visualization platform was used to correct the critical temperature field obtained by simulation, and the real critical temperature field was about 170 °C. In the randomized trials, the simulated and actual area ratio of skin layer were in good agreement, with a maximum deviation of 8.9%, which proved that it was reliable to estimate the skin layer area ratio based on theoretical critical temperature field through the change of molding parameters, and then to predict the performance change of the parts.     

Multidimensional HRGC for sample components with a wide range of volatilities and polarities

A diverse mixture of volatile headspace analytes containing compounds with boiling points covering a range from ?196°c to 145°c can be separated in approximately 40 minutes by multidimensional HRGC. The described provisional MD-HRGC Systems employ cryogenic sample collection, four 0.53 mm FSOT columns, and multi-ramp temperature programming of either one or two ovens. Enhanced sensitivity for organic species and minimal interference from water vapour in the samples can be obtained by a MD-HRGC configuration that uses separate ovens, appropriate column switching operations, and TCD + FID detection.     

Liquid range temperature of ionic liquids as potential working fluids for absorption heat pumps

The liquid range temperature of six ionic liquids (ILs) was determined in this work with the aim to propose suitable absorbents for heat pump systems. The selected ILs have three different cations, imidazolium, pyridinium and choline and each was combined with four different anions [NTf₂]⁻, [OTf]⁻, [MeSO₃]⁻ and [BETI]⁻. The lower limit, given by solid − liquid transitions, was determined using differential scanning calorimetry (DSC). The upper limit is given by the degradation temperature. This temperature is determined using thermogravimetric technique (TGA). Dynamic and isothermal methods have been combined to estimate the maximum operation temperature. ILs ageing effect was also analysed in this work.     

基于微机电加工技术芯片的量热式生物传感器的测热性能研究

采用鸡肝酯酶作为生物敏感元件,以基于微机电加工技术制作的NCM9924微量热芯片作为换能器,建立了用于农药的残留量测定的量热式生物传感器试验系统。应用此系统进行了量热芯片灵敏度、酶促反应放热和农药抑制试验研究。结果表明:在流量为0.5mL·min-1的情况下,换能器的温度灵敏度不低于1.184mV·K-1;本系统对同一酶活水平的放热量响应具有良好的重现性。鸡肝酯酶被2mg·L-1甲胺磷农药抑制后,系统放热曲线的峰高降低了50%。     

Theoretical study of temperature influence on the electrophoresis of a pH-regulated polyelectrolyte

The influence of temperature on the electrophoresis of a spherical, pH-regulated polyelectrolyte (PE) particle having both acidic and basic functional groups in an aqueous salt solution containing multiple ionic species is investigated theoretically. The type of particle considered simulates entities including proteins, biomolecules, and synthetic polymers. The applicability of the model proposed is verified by the experimental data of succinoglycan nanoparticles reported in the literature. Taking a glycin PE as an example, the variations of its mobility with the temperature, bulk salt concentration, and pH are examined through numerical simulation. Empirical relationships that correlate the mobility with these factors are obtained for temperature, bulk salt concentration, and pH ranging from 293 to 308 K, 10⁻⁴ to 10⁻² M, and 2-10.5, respectively. Several interesting and important results for the PE mobility are observed. These results provide not only valuable information for interpreting experimental data but also for designing electrophoresis devices where temperature can play a role.