Temperature and Frequency Dependence of the Dynamic Deformation and Losses of Elastomers

1963 ◽  
Vol 36 (3) ◽  
pp. 709-718
Author(s):  
G. M. Bartenev ◽  
Yu V. Zelenev
Keyword(s):  
Frequency Dependence ◽  
Dynamic Deformation ◽  
Relaxation Times ◽  
Qualitative Description ◽  
Relaxation Processes ◽  
Mechanical Loss ◽  
Chain Molecules ◽  
Chemical Crosslinks ◽  
Loss Maximum ◽  
High Temperature Maximum

Abstract The results of this investigation of the temperature and frequency dependence of the deformation and mechanical loss of elastomeric network polymers in the temperature range from −90 to +120° C may be understood on the basis of the conceptions of three types of relaxation processes in these materials: orientation of the units of the chain molecules, overcoming of the secondary crosslinks (entanglements) in the movement of the segments, and the process of destruction of the polysulfide bonds, which comprise quite a small part of the total number of the chemical crosslinks. The first process is connected with the glass-transition and leads to the occurrence of a low-temperature maximum of mechanical losses, while the third leads to a high-temperature maximum. The first and third relaxation processes are apparently characterized by narrow spectra of relaxation times, which may be substituted for approximately by the corresponding averaged relaxation times. For the second process the spectrum of relaxation times is probably very wide and it is not possible to make the analogous substitution; this also explains the absence of a third mechanical loss maximum and the occurrence of a well marked frequency dependence of the deformation amplitude in the high-elastic range. The models of a network polymer considered for low and high temperatures give a qualitative description of all the main mechanical properties of these materials.

Relaxation processes of some simple aliphatic molecules in dilute solutions

1977 ◽  
Vol 55 (4) ◽  
pp. 297-301 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Carbon Tetrachloride ◽  
Dielectric Relaxation ◽  
Thermodynamic Parameters ◽  
Relaxation Times ◽  
Relaxation Processes ◽  
Dilute Solutions ◽  
Microwave Region ◽  
Nonpolar Solvents ◽  
Dielectric Data ◽  
Intramolecular Rotation

The dielectric relaxation processes of acetone, cyclohexanone, 4-methyl-2-pentanone, and 4-heptanone in dilute nonpolar solvents, n-heptane, cyclohexane, benzene, and carbon tetrachloride have been studied in the microwave region over a temperature range 10 to 60 °C. The relaxation times and the thermodynamic parameters for the activated states have been determined using the measured dielectric data. The results have been discussed in terms of dipole reorientation by molecular and intramolecular rotation and compared, wherever possible, with other similar studies on aliphatic molecules.

Relaxation processes of quinoline, isoquinoline, and their mixtures

1980 ◽  
Vol 58 (1) ◽  
pp. 20-24 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Thermodynamic Parameters ◽  
Molecular Motion ◽  
Polar Solvent ◽  
Relaxation Times ◽  
Relaxation Processes ◽  
Polar Components ◽  
Dielectric Absorption ◽  
System A ◽  
Dielectric Data ◽  
Activated State

The dielectric absorption of quinoline, isoquinoline, and their binary mixtures has been studied in the microwave region over a range of temperatures in dilute benzene and n-heptane solutions. The relaxation times and the thermodynamic parameters for the activated state have been determined using the measured dielectric data. The results obtained have been discussed in terms of the molecular motion of the system. A relation has been proposed to represent the relaxation behavior of a system of two Debye-type polar components in a non-polar solvent. The relation has been tested by comparing the calculated values with those determined experimentally for a few systems consisting of similar, simple rigid polar molecules.

Temperature Dependence of Dynamic Properties of Elastomers. Relaxation Distributions

1952 ◽  
Vol 25 (4) ◽  
pp. 720-729 ◽  
Author(s):  
John D. Ferry ◽  
Edwin R. Fitzgerald ◽  
Lester D. Grandine ◽  
Malcolm L. Williams
Keyword(s):  
Distribution Function ◽  
Temperature Dependence ◽  
Dynamic Properties ◽  
Relaxation Times ◽  
Dynamic Mechanical Properties ◽  
Relaxation Processes ◽  
The Real ◽  
Reduced Frequency ◽  
Dynamic Rigidity ◽  
Composite Curve

Abstract By the use of reduced variables, the temperature dependence and frequency dependence of dynamic mechanical properties of rubberlike materials can be interrelated without any arbitrary assumptions about the functional form of either The definitions of the reduced variables are based on some simple assumptions regarding the nature of relaxation processes. The real part of the reduced dynamic rigidity, plotted against the reduced frequency, gives a single composite curve for data over wide ranges of frequency and temperature; this is true also for the imaginary part of the rigidity or the dynamic viscosity. The real and imaginary parts of the rigidity, although independent measurements, are interrelated through the distribution function of relaxation times, and this relation provides a check on experimental results. First and second approximation methods of calculating the distribution function from dynamic data are given. The use of the distribution function to predict various types of time-dependent mechanical behavior is illustrated.

Relaxation Time Spectrum, Elasticity, and Viscosity of Rubber. I

1954 ◽  
Vol 27 (1) ◽  
pp. 36-54 ◽  
Author(s):  
W. Kuhn ◽  
O. Künzle ◽  
A. Preissmann
Keyword(s):  
Relaxation Time ◽  
Relaxation Times ◽  
Time Spectrum ◽  
Test Sample ◽  
Elastic Behavior ◽  
Relaxation Processes ◽  
Relaxation Time Spectrum ◽  
Restoring Force ◽  
Constant Length ◽  
Rapid Deformation

Abstract By rapid deformation of a medium in which linear molecules are present, various changes are produced simultaneously in the latter. These changes are more or less independent of one another, and can release independently and totally or partially by rearrangement of valence distances and valence angles in the chain molecules. By virtue of such relaxation processes, a portion of the stress originating in the rapid deformation disappears, with a changing time requirement for the various portions. A relaxation time spectrum is thus formed. The relaxation time spectrum consists of a finite number of restoring force mechanisms with proper relaxation times or of a continuous spectrum. Both the creep curves (the dependence of the length of a body on time at constant load), and stress relaxation (decay of the stress observed in test sample kept at constant length after rapid deformation), as well as the total visco-elastic behavior, especially the behavior at constant periodic deformation of the test sample, are determined by the relaxation time spectrum. The appropriate Quantitative relationships were derived.

scholarly journals A Bis-Monophospholyl Dysprosium Cation Showing Magnetic Hysteresis at 48 Kelvin

2019 ◽  
Author(s):  
Peter Evans ◽  
Daniel Reta ◽  
George F. S. Whitehead ◽  
Nicholas Chilton ◽  
David Mills
Keyword(s):  
Data Storage ◽  
Single Molecule ◽  
Structural Changes ◽  
Elevated Temperatures ◽  
Spin Dynamics ◽  
Magnetic Hysteresis ◽  
Relaxation Times ◽  
Magnetic Memory ◽  
Relaxation Processes ◽  
Potential Applications

Single-molecule magnets (SMMs) have potential applications in high-density data storage, but magnetic relaxation times at elevated temperatures must be increased to make them practically useful. <i>Bis</i>-cyclopentadienyl lanthanide sandwich complexes have emerged as the leading candidates for SMMs that show magnetic memory at liquid nitrogen temperatures, but the relaxation mechanisms mediated by aromatic C<sub>5</sub> rings have not been fully established. Here we synthesise a <i>bis</i>-monophospholyl dysprosium SMM [Dy(Dtp)<sub>2</sub>][Al{OC(CF<sub>3</sub>)<sub>3</sub>}<sub>4</sub>] (<b>1</b>, Dtp = {P(C<sup>t</sup>BuCMe)<sub>2</sub>}) by the treatment of <i>in situ</i>-prepared “[Dy(Dtp)<sub>2</sub>(C<sub>3</sub>H<sub>5</sub>)]” with [HNEt<sub>3</sub>][Al{OC(CF<sub>3</sub>)<sub>3</sub>}<sub>4</sub>]. SQUID magnetometry reveals that <b>1</b> has an effective barrier to magnetisation reversal of 1,760 K (1,223 cm<sup>–1</sup>) and magnetic hysteresis up to 48 K. <i>Ab initio</i> calculation of the spin dynamics reveal that transitions out of the ground state are slower in <b>1</b> than in the first reported dysprosocenium SMM, [Dy(Cp<sup>ttt</sup>)<sub>2</sub>][B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] (Cp<sup>ttt</sup> = C<sub>5</sub>H<sub>2</sub><sup>t</sup>Bu<sub>3</sub>-1,2,4), however relaxation is faster in <b>1</b> overall due to the compression of electronic energies and to vibrational modes being brought on-resonance by the chemical and structural changes introduced by the <i>bis</i>-Dtp framework. With the preparation and analysis of <b>1</b> we are thus able to further refine our understanding of relaxation processes operating in <i>bis</i>-C<sub>5</sub>/C<sub>4</sub>P sandwich lanthanide SMMs, which is the necessary first step towards rationally achieving higher magnetic blocking temperatures in these systems in future.

scholarly journals The Dynamic Properties of 5Cb Filled with Aerosil Particles Investigated by Pcs

1999 ◽  
Vol 559 ◽  
Author(s):  
F.M. Aliev ◽  
M. Kreuzer ◽  
Yu.P. Panarin
Keyword(s):  
Liquid Crystal ◽  
Temperature Dependence ◽  
Relaxation Process ◽  
Nematic Liquid Crystal ◽  
Broad Spectrum ◽  
Dynamic Properties ◽  
Relaxation Times ◽  
Correlation Spectroscopy ◽  
Relaxation Processes ◽  
Optoelectronic Application

ABSTRACTNematic liquid crystal filled with Aerosil particles, a prospective composite material for optoelectronic application, has been investigated by static light scattering and Photon Correlation Spectroscopy (PCS). The Aerosil particles in filled nematic liquid crystals (FN) form a network structure with LC domains about 2500 Å in size with a random distribution of the director orientation of each domain.We found that the properties of 5CB are considerably affected by the network. The N-I phase transition in filled 5CB was found to be smeared out and depressed. PCS experiments show that two new relaxation processes appear in filled 5CB in addition to the director fluctuation process in bulk. The slow relaxation process, with a broad spectrum of relaxation times, is somewhat similar to the slow decay, which is observed in confined nematic liquid crystal.The middle frequency process was assigned to the director fluctuations in the surface layer formed at the particle-LC interface. The decay function describing this relaxation process is a stretched exponential (β ≍ 0.7). The temperature dependence of the relaxation times of the middle frequency obeys the Vogel-Rilcher law. Such a temperature dependence, accompanied by a broad spectrum of relaxation times suggests that the dynamics of the director fluctuations near the Aerosil particle-LC interface is glass-like.

Measurement of spin–phonon transition probabilities in ruby

1970 ◽  
Vol 48 (9) ◽  
pp. 1099-1103 ◽  
Author(s):  
M. El-Azab ◽  
C. F. Weissfloch
Keyword(s):  
Transition Probabilities ◽  
Relaxation Times ◽  
Phase Method ◽  
Relaxation Processes ◽  
Spin Lattice ◽  
X Band ◽  
Coupling Parameters ◽  
Lattice Coupling ◽  
Phonon Transition ◽  
Spin Phonon Transition

Measurements at X-band frequencies of relaxation times and spin–phonon transition probabilities in ruby grown by the "vapor phase" method were carried out. They demonstrate the existence of relaxation processes which cannot be related to the spin–lattice coupling parameters obtained from ultrasonic and static stress experiments.

Relaxation Processes in the N-Methyl Group of 1,2,2,6,6-Pentamethylpiperidine

1990 ◽  
Vol 43 (2) ◽  
pp. 447 ◽  
Author(s):  
ID Rae ◽  
ML Woolcock
Keyword(s):  
Relaxation Times ◽  
Spin Rotation ◽  
Relaxation Processes ◽  
Methyl Group ◽  
Methyl Methyl ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects

Relaxation times (T1) and methyl-methyl nuclear Overhauser effects were measured for 1H, 13C and 2H nuclei in 1,2,2,6,6-pentamethylpiperidine and its N-CHD2 analogue which was synthesized by LiAlD4 reduction of the N-CHO compound. The relaxation pathways for hydrogens of the N-CH3 group were estimated to be as follows: spin-rotation 0.046 s-1, dipole-dipole within N-methyl 0.069 s-1, and dipole-dipole with the hydrogens of the C- methyls 0.027 s-1. The 1H{1H) Overhauser effect at the N-CH3 was 7.6%.

Energy transfer in polyatomic molecules. II. Relative catalytic efficiency for energy transfer to different vibrations to the same molecule

1961 ◽  
Vol 264 (1318) ◽  
pp. 299-308 ◽  
Keyword(s):  
Energy Transfer ◽  
Sulphur Dioxide ◽  
Deuterium Oxide ◽  
Relaxation Times ◽  
Catalytic Efficiency ◽  
Polyatomic Molecules ◽  
Fair Agreement ◽  
Water Molecules ◽  
Relaxation Processes ◽  
Ultrasonic Measurements

Vibrations of sulphur dioxide show two separate relaxation times. Values of r 1 = 6.0 × 10 -8 s for the vibrations of 519 cm -1 and r 2 = 1.2 × 10 -6 s for the vibrations of 1151 and 1361 cm -1 have been derived from new ultrasonic measurements, in fair agreement with earlier work. Molecules studied as possible vibration-translation catalysts included ethane, ethylene, water, and n -hexane. No enhanced efficiency of energy transfer was observed with ethylene. Ethane and water molecules were found to be only moderately efficient catalysts; proportionally, they exert a greater effect for processes associated with r 1 . Deuterium oxide is found to be somewhat more efficient than water. n -Hexane is highly efficient for both the r 1 and r 2 relaxation processes of sulphur dioxide. These observations are discussed in relation to various mechanisms for the catalysis of energy transfer.

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