Low Temperature Characteristics of Elastomers

1948 ◽  
Vol 21 (1) ◽  
pp. 94-111
Author(s):  
S. D. Gehman ◽  
D. E. Woodford ◽  
C. S. Wilkinson
Keyword(s):  
Chemical Composition ◽  
Low Temperature ◽  
Low Temperatures ◽  
Freezing Point ◽  
Butyl Rubber ◽  
Dry Ice ◽  
X Ray ◽  
Critical Measure ◽  
Cold Room ◽  
High Elasticity

Abstract The low temperature stiffening of elastomers frequently limits their usefulness. A new laboratory test for measuring their stiffness at low temperatures is described. Strips of the stocks to be tested are mounted around a cylindrical rack in a vertical, cylindrical insulated chamber. The temperature in the chamber is controlled by cooling the base externally with dry ice and by a moderate regulated flow of precooled air through dry ice in the bottom of the chamber. This system gives stable temperatures which are easily controlled. The chamber can be rotated to attach the samples in succession, by means of projecting top grips, to a suitably mounted torsion wire. The stiffness is measured by the angle of twist of the sample when the torsion head is rotated 180°. The relative modulus for any temperature is calculated as the ratio of the modulus at this temperature to that at 25° C. Plots of angle of twist against temperature show a rather sharp break at the low temperature end of the curve. This determines a somewhat subjective “freezing point”. Curves are given to illustrate the wide variety of low temperature stiffening characteristics for elastomers. In unplasticized stocks the chemical composition of the monomers is the dominating factor for these properties for various synthetic rubbers. The stiffness of elastomers which are capable of crystallization on stretching, such as Hevea, Neoprene, and Butyl rubber, depends not only on temperature but also on time of exposure. To study these effects, the foregoing apparatus was used in a cold room. A rather long induction period occurs, during which the stiffness is essentially constant. It then increases and eventually reaches a larger constant value. Several months may be required to complete these changes. x-Ray examination of Hevea and Butyl proved that the increased stiffness on long exposure is due to crystallization. No change was observed in the stiffness of GR-S in the period of 2.5 months at − 30° C. Reduction in the speed of retraction is a critical measure of the deterioration of high elasticity at low temperatures. It gives a wide differeniation at moderately low temperatures between Butyl rubber and Hevea or GR-S, whereas a slow modulus test does not.

scholarly journals Chemical Composition and Low-Temperature Fluidity Properties of Jet Fuels

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1184
Author(s):  
Alirio Benavides ◽  
Pedro Benjumea ◽  
Farid Cortés ◽  
Marco Ruiz
Keyword(s):  
Chemical Composition ◽  
Low Temperature ◽  
Low Temperatures ◽  
Freezing Point ◽  
Structural Characteristics ◽  
Jet Fuels ◽  
Weight Percentage ◽  
Compositional Approach ◽  
Composition Property ◽  
Crystallization Onset

The physicochemical properties of petroleum-derived jet fuels mainly depend on their chemical composition, which can vary from sample to sample as a result of the diversity of the crude diet processed by the refinery. Jet fuels are exposed to very low temperatures both at altitude and on the ground in places subject to extreme climates and must be able to maintain their fluidity at these low temperatures otherwise the flow of fuel to turbine engines will be reduced or even stopped. In this work, an experimental evaluation of the effect of chemical composition on low-temperature fluidity properties of jet fuels (freezing point, crystallization onset temperature and viscosity at −20 °C) was carried out. Initially, a methodology based on gas chromatography coupled to mass spectrometry (GC–MS) was adapted to determine the composition of 70 samples of Jet A1 and Jet A fuels. This methodology allowed quantifying the content, in weight percentage, of five main families of hydrocarbons: paraffinic, naphthenic, aromatic, naphthalene derivatives, and tetralin- and indane-derived compounds. Fuel components were also grouped into 11 classes depending on structural characteristics and the number of carbon atoms in the compound. The latter compositional approach allowed obtaining more precise model regressions for predicting the composition–property dependence and identifying individual components or hydrocarbon classes contributing to increased or decreased property values.

FEC-LiTFSI-Pyr1ATFSI Ionic Liquid Electrolyte to Improve Low Temperature Performance of Lithium-Ion Batteries

2014 ◽  
Vol 986-987 ◽  
pp. 80-83
Author(s):  
Xiao Xue Zhang ◽  
Zhen Feng Wang ◽  
Cui Hua Li ◽  
Jian Hong Liu ◽  
Qian Ling Zhang
Keyword(s):  
Low Temperature ◽  
Lithium Ion Batteries ◽  
Low Temperatures ◽  
Freezing Point ◽  
Lithium Ion ◽  
Liquid Electrolyte ◽  
Capacity Retention ◽  
Composite Electrolyte ◽  
Ionic Liquid Electrolyte ◽  
Fluoroethylene Carbonate

N-methyl-N-allylpyrrolidinium bis (trifluoromethanesulfonyl) imide (PYR1ATFSI) with substantial supercooling behavior is synthesized to develop low temperature electrolyte for lithium-ion batteries. Additive fluoroethylene carbonate (FEC) in LiTFSI/PYR1ATFSI/EC/PC/EMC is found that it can reduce the freezing point. LiFePO4/Li coin cells with the FEC-PYR1ATFSI electrolyte exhibit good capacity retention, reversible cycling behavior at low temperatures. The good performance can be attributed to the decrease in the freezing point and the polarization of the composite electrolyte.

scholarly journals The Stability of Icosahedral Cd-Yb

2003 ◽  
Vol 805 ◽  
Author(s):  
Günter Krauss ◽  
Sofia Deloudi ◽  
Andrea Steiner ◽  
Walter Steurer ◽  
Amy R. Ross ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ambient Temperature ◽  
Mechanical Stress ◽  
Single Crystals ◽  
High Temperatures ◽  
Low Temperatures ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Stability

ABSTRACTThe stability of single-crystalline icosahedral Cd-Yb was investigated using X-ray diffraction methods in the temperature range 20 K ≤ T ≤ 900 K at ambient pressure and from ambient temperature to 873 K at about 9 GPa. Single-crystals remain stable at low temperatures and in the investigated HP-HT-regime. At high temperatures and ambient pressure, the quasicrystal decomposes. The application of mechanical stress at low temperatures yields to the same decomposition, the formation of Cd. A reaction of icosahedral Cd-Yb with traces of oxygen or water causing the decomposition seems reasonable, but a low-temperature instability of this binary quasi-crystal cannot be ruled out totally.

The determination of composition and thermal history of plagioclase by the X-ray powder method

1955 ◽  
Vol 30 (229) ◽  
pp. 648-656 ◽  
Author(s):  
J. Goodyear ◽  
W. J. Duffin
Keyword(s):  
Chemical Composition ◽  
Low Temperature ◽  
Similar Composition ◽  
X Ray ◽  
Naturally Occurring ◽  
Cell Dimensions ◽  
History Of ◽  
Unit Cell Dimensions ◽  
Ray Patterns

In a recent paper (hereafter referred to as GD) Goodyear and Dufiln (1954) described X-ray powder data for a number of synthetic and chemically analysed plagioclases of composition An0Abl00-Anl00Ab0. Important aspects of this work were a correlation of the X-ray patterns with chemical composition, and a distinction between the pattern of a naturally occurring material of low-temperature origin and that of a synthetic of similar composition. The investigation showed quite clearly that the unit-cell dimensions of a synthetic plagioelase depend but little on composition from An0Abl00 to An70Ab30, whilst they differ from those of the low-temperature modification greatly for albite, to a lessening degree as the composition approaches An70Ab30, and practically not at all in the range An70Ab30-Anl00Ab0.

Digital X-Ray Flat Panel Housing for Operation at Extremely Low Temperatures

2019 ◽  
Vol 942 ◽  
pp. 68-76
Author(s):  
Fedor Simankin ◽  
Jan Miciński ◽  
Evgeniy Shumnyi ◽  
Alexander Shtein ◽  
Ablay Zhunusov
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Three Dimensional ◽  
Wall Structure ◽  
Flat Panel ◽  
Three Dimensional Printing ◽  
X Ray ◽  
Temperature Conditions ◽  
Dimensional Printing

The paper presents the housing wall structure for the digital X-ray flat panel which can operate in extremely low temperature conditions. A technology of three-dimensional printing is proposed for making the detector housing with heat conductors incorporated in its wall structure.

Low-Temperature (<300°C) Phosphate Ceramics from Reactive Aluminas

1989 ◽  
Vol 179 ◽  
Author(s):  
M. R. Silsbee ◽  
R. A. Steinke ◽  
D. M. Roy ◽  
D. K. Agrawal ◽  
R. Roy
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Low Temperatures ◽  
Ceramic Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Characterization Techniques ◽  
Exciting Potential

AbstractReactive aluminas, including rapidly calcined gibbsites, offer exciting potential for forming ceramic materials at low temperatures. New x-ray amorphous aluminas will react with water at room temperatures to form compacts with 10–50 MPa tensile strengths, via viscous slurries. The cementious behavior of these materials has been examined. The results of TGA, x-ray diffraction, SEM, mechanical properties, and other characterization techniques, as applied to these systems, will be discussed.

Kinetically asymmetric charge and discharge behavior of LiNi0.5Mn1.5O4 at low temperature observed by in situ X-ray diffraction

2014 ◽  
Vol 2 (37) ◽  
pp. 15414-15419 ◽  
Author(s):  
Ikuma Takahashi ◽  
Haruno Murayama ◽  
Kenji Sato ◽  
Takahiro Naka ◽  
Koji Kitada ◽  
...  
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Discharge Behavior

Thermodynamically reversible LiNi0.5Mn1.5O4 electrodes kinetically behave asymmetrically during charging and discharging at low temperatures.

The Thermal Deformation of Cement-Based Material at Low Temperatures

2014 ◽  
Vol 1081 ◽  
pp. 279-283 ◽  
Author(s):  
Nan Zhang ◽  
Juan Liao ◽  
Tao Zhang ◽  
Wen Zhan Ji
Keyword(s):  
Low Temperature ◽  
Cement Paste ◽  
Low Temperatures ◽  
Thermal Deformation ◽  
Pore Solution ◽  
Freezing Point ◽  
Bulk Solution ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Cement Based Materials

Thermal deformation of concrete at low temperature expands from-20°C to-50°C and contracts from-30°C to-10°C. Based on previous studies, the paper tries to explain the deformaion trend by analyzing freezing point of bulk solution and pore solution in saturated hardened cement paste. The result shows that it is critical to thermal deformation of cement-based materials at low temperature that pore solution in the pores smaller than 8 nm freezes.

Accurate charge densities in days — use of synchrotrons, image plates and very low temperatures

1999 ◽  
Vol 55 (3) ◽  
pp. 363-374 ◽  
Author(s):  
B. B. Iversen ◽  
F. K. Larsen ◽  
A. A. Pinkerton ◽  
A. Martin ◽  
A. Darovsky ◽  
...  
Keyword(s):  
Low Temperature ◽  
Electron Density ◽  
Diffraction Data ◽  
Low Temperatures ◽  
Systematic Errors ◽  
Reciprocal Space ◽  
Synchrotron Source ◽  
X Ray ◽  
Single Temperature ◽  
Very Low Temperature

Extensive synchrotron (28 K) and conventional sealed-tube (9 K) X-ray diffraction data have been collected on tetrakis(dimethylphosphinodithioato-S,S′)thorium(IV), [Th(S2PMe2)4]. The use of very low temperatures, well below those obtained with liquid-nitrogen cooling, is crucial for the accuracy of the data. This is due to minimization of temperature-dependent systematic errors such as TDS and anharmonicity, and extension and intensification of the data in reciprocal space. Comparison of structural parameters derived separately from the sealed-tube data and the synchrotron data shows good agreement. The synchrotron data are markedly superior when comparing refinement residuals, standard uncertainties (s.u.'s) of the data and s.u.'s of the derived parameters. However, the study suggests that there are still small uncorrected systematic errors in the data. The very large extent [(\sin\theta/\lambda)max = 1.77 Å−1] of the synchrotron data and the very low temperature at which they were collected makes it possible to separate anharmonic effects from electron-deformation effects even with only an X-ray data set at a single temperature. The electron density shows a large polarization of the outer Th core of d-type symmetry. This deformation is successfully modelled with contracted multipolar functions, which are only slightly correlated with anharmonic expansions in reciprocal space when using the full extent of the data. In the data collection more than a factor of 100 in speed is gained by use of image-plate area detectors at the synchrotron source compared with conventional sequential measurements. Thus accurate, very low temperature synchrotron-radiation diffraction data can now be measured within days, which makes electron-density studies of compounds beyond the first transition series more frequently within reach.

Low Temperature Studies Of Rare Gases Adsorbed On Molecular Sieve Materials

1991 ◽  
Vol 233 ◽  
Author(s):  
Graham F. Mccann ◽  
I. Gameson ◽  
W.J. Steado ◽  
T. Rayment ◽  
P.J. Barrie ◽  
...  
Keyword(s):  
Low Temperature ◽  
Phase Transformations ◽  
Adsorption Isotherms ◽  
Low Temperatures ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Variable Temperature ◽  
Rare Gases ◽  
X Ray Diffraction ◽  
X Ray

ABSTRACTX-ray diffraction (XRD) and adsorption isotherms have long been traditional methods of characterising molecular sieves. By combining these techniques at low temperatures with variable temperature 129-Xe N.M.R. we now have a fuller understanding of the behaviour of sorbed layers inside these materials. In particular we have observed phase transformations of Xe in a polyhydroxyaluminium-pillared montmorillonite molecular sieve and have developed a model consistent with the data. In addition, using XRD, an interpillar distance of ca. 30Å was calculated. We present the first detailed low temperature studies of 129-Xe N.M.R. on these systems.

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