Designing With Elastomers for Use At Low Temperatures, Near Or Below Glass Transition

1976 ◽  
Author(s):  
Keyword(s):  
Glass Transition ◽  
Low Temperatures

Glass Transition and Ultrasonic Relaxation in Polystyrene

1996 ◽  
Vol 455 ◽  
Author(s):  
A. Sahnoune ◽  
L. Piché
Keyword(s):  
Molecular Weight ◽  
Relaxation Time ◽  
Glass Transition ◽  
Low Temperatures ◽  
Relaxation Modulus ◽  
Low Molecular Weight ◽  
Relaxation Model ◽  
Fragility Index ◽  
Molecular Weights ◽  
Ultrasonic Relaxation

ABSTRACTWe present measurements of the glass transition and the ultrasonic relaxation modulus in a series of monodisperse polystyrenes. The temperature dependence of the modulus was analyzed using Havriliak-Negami relaxation model (HN) and Vogel-Tammann-Fulcher equation (VTF) for the relaxation time. The results allowed us to determine the fragility index, m, which decreases with increasing molecular weight, Mn. Furthermore, the relaxation time was found to saturate at high molecular weights and varies as Mnp, in the low molecular weight region. The exponent is p≈2 at high temperatures and p ≈ 7 at low temperatures close to Tg.

Superconducting Properties and Possible Vortex Phase Diagram in a Thick Amorphous MgxB1-xFilm

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3688-3693 ◽  
Author(s):  
S. Okuma ◽  
S. Togo ◽  
K. Amemori
Keyword(s):  
Phase Diagram ◽  
Glass Transition ◽  
Low Temperatures ◽  
Superconducting Properties ◽  
Vortex Phase Diagram ◽  
Vortex Phase ◽  
Current Voltage ◽  
Large Vortex ◽  
Field Temperature ◽  
Current Voltage Characteristics

We report on the superconducting properties in a thick amorphous Mg x B 1-x film, which was prepared by coevaporation of pure Mg and B. Measurements of the current-voltage characteristics and the AC complex resistivity in magnetic fields indicate the presence of the vortex-glass transition. Based on the data, we construct the possible phase diagram in the field-temperature plane. We find that there is the large vortex-liquid phase, which persists down to low temperatures.

SIMULATING THE EFFECT OF POISSON RATIO ON METALLIC GLASS PROPERTIES

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1229-1234 ◽  
Author(s):  
JAMES R. MORRIS ◽  
RACHEL S. AGA ◽  
TAKESHI EGAMI ◽  
VALENTIN A. LEVASHOV
Keyword(s):  
Glass Transition ◽  
Liquid Phase ◽  
Metallic Glass ◽  
Low Temperatures ◽  
Poisson Ratio ◽  
Liquid Structure ◽  
Higher Temperature ◽  
Measurable Change ◽  
Lower Melting Temperature ◽  
Glass Properties

Recent work has shown that many metallic glass properties correlate with the Poisson ratio of the glass. We have developed a new model for simulating the atomistic behavior of liquids and glasses that allows us to change the Poisson ratio, while keeping the crystalline phase cohesive energy, lattice constant, and bulk modulus fixed. A number of liquid and glass properties are shown to be directly affected by the Poisson ratio. An increasing Poisson ratio stabilizes the liquid structure relative to the crystal phase, as indicated by a significantly lower melting temperature and by a lower enthalpy of the liquid phase. The liquids clearly exhibit two changes in behavior: one at low temperatures, associated with the conventional glass transition Tg, and a second, higher temperature change associated with the shear properties of the liquids. This second crossover has a characteristic, measurable change in the liquid structure.

First and Second Order Transitions in Neoprene

1961 ◽  
Vol 34 (2) ◽  
pp. 668-685 ◽  
Author(s):  
R. M. Murray ◽  
J. D. Detenber
Keyword(s):  
Glass Transition ◽  
Crystallization Temperature ◽  
Minimum Temperature ◽  
Low Temperatures ◽  
Crystallization Rate ◽  
General Purpose ◽  
Second Order ◽  
Brittleness Temperature

Abstract Neoprene vulcanizates crystallize most rapidly at —12° C. The temperature at which a vulcanizate is crystallized determines the minimum temperature at which it will thaw, the thaw point being approximately 15° C higher than the crystallization temperature over the range studied. Brittleness temperature is not changed as a result of crystallization. Crystallization resistance of the general purpose dry neoprene types increases in the following order: W, WB, WX, GN, GRT, WRT. Depending on the neoprene type, crystallization is retarded by a factor of 5 to 10 by vulcanization. Variation of filler type does not change crystallization rate appreciably. Crystallization rate is retarded through the use of sulfur, certain resinous type plasticizers, as well as by increased state of cure. Ester plasticizers which depress brittleness tempterature and reduce stiffening at low temperatures increase crystallization rate considerably and permit crystallization to occur at very low temperatures. Brittleness and 10,000 psi stiffness temperatures are not affected appreciably by neoprene type, state of cure, or amount and type of filler. Glass transition is approximately 12° C lower than the 10,000 psi stiffness temperature and 6° C lower than the brittleness temperature.

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