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.

TECHALLOY NICKEL 200

Alloy Digest ◽  
1977 ◽  
Vol 26 (6) ◽  
Keyword(s):  
Physical Properties ◽  
Surface Treatment ◽  
Low Temperatures ◽  
Nickel Alloys ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
General Purpose ◽  
Commercially Pure ◽  
Electrical Components ◽  
Nickel 200

Abstract TECHALLOY Nickel 200 is commercially pure wrought nickel. It maintains good strength at elevated temperatures and is tough and ductile at low temperatures. It is a general-purpose material when the properties of nickel alloys are not needed. Its many uses include spun and cold-formed parts, electrical components, transducers and nickel-cadmium batteries. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-246. Producer or source: Techalloy Company Inc..

scholarly journals SECOND-ORDER CORRECTIONS TO QED COUPLING AT LOW TEMPERATURE

2008 ◽  
Vol 23 (29) ◽  
pp. 4709-4719 ◽  
Author(s):  
SAMINA S. MASOOD ◽  
MAHNAZ HASEEB
Keyword(s):  
Low Temperatures ◽  
Vacuum Polarization ◽  
Second Order ◽  
Electromagnetic Properties ◽  
Electron Mass ◽  
Polarization Tensor ◽  
Coupling Constant ◽  
Electric Permittivity ◽  
Thermal Medium ◽  
Vacuum Polarization Tensor

We calculate the second-order corrections to vacuum polarization tensor of photons at low temperatures, i.e. T ≪ 1010 K (T ≪ me). The thermal contributions to the QED coupling constant are evaluated at temperatures below the electron mass that is T < me. Renormalization of QED at these temperatures has explicitly been checked. The electromagnetic properties of such a thermal medium are modified. Parameters like electric permittivity and magnetic permeability of such a medium are no more constant and become functions of temperature.

Elastomer Structures and ‘Cold Crystallization’

1979 ◽  
Vol 52 (1) ◽  
pp. 207-212 ◽  
Author(s):  
M. Bruzzone ◽  
E. Sorta
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Melting Point ◽  
Natural Rubber ◽  
Crystallization Rate ◽  
Cold Crystallization ◽  
Structural Defects ◽  
Strain Induced Crystallization ◽  
Induced Crystallization

Abstract In a great number of applications an ideal elastomer should satisfy, to a certain extent, both of the following requirements: (1) nearly instantaneous crystallization upon application of strain (strain induced crystallization) and (2) slow or no crystallization when cooled at the temperature of maximum crystallization rate (cold induced crystallization). A noteworthy case of (2) is elastomer crystallization in a strained state. The connection between the points (1) and (2) has not been clearly understood up to now, but it is known that some crystallizable elastomers fulfil the requirements of both (1) and (2) better than others. From an experimental point of view, cold induced crystallization kinetics are substantially easier to measure than those of very fast strain induced crystallization. The phenomenon of cold induced crystallization in natural rubber, NR, has been known since the very beginning of elastomer technology and the tendency of natural rubber to crystallize by cooling has been overcome by crosslinking it with sulphur (vulcanization) without impairing its ability to crystallize by stretching (Goodyear, 1836). The synthesis of cis-polyisoprenes (IR) and cis-polybutadiene (BR) of different microstructural purity (different cis content) gave the possibility of changing the crystallization rate. It has also been reported that the very fast cold crystallization of trans-polypentenamer (TPA) could be reduced by lowering the trans content. The same fact had been observed earlier for trans-polychloroprene. There is a general agreement in postulating that the reduction of the crystallization rate, obtained either by cross-linking or by chain regularity reduction, can be linked with the lowering of the melting point. In both cases the low level of structural defects introduced in the chains does not affect the glass transition temperature in such a way as to vary the crystallization rate. The aim of this paper is to emphasize the importance of the variations of the glass transition temperature and melting point on the elastomeric cold crystallization rate and the way these may be used in planning new elastomer structures.

Study of the reaction mechanism between electroless Ni–P and Sn and its effect on the crystallization of Ni–P

2003 ◽  
Vol 18 (1) ◽  
pp. 4-7 ◽  
Author(s):  
Y. C. Sohn ◽  
Jin Yu ◽  
S. K. Kang ◽  
W. K. Choi ◽  
D. Y. Shih
Keyword(s):  
Reaction Mechanism ◽  
Solid State ◽  
Solid State Reaction ◽  
Crystallization Temperature ◽  
Low Temperatures ◽  
Transformation Temperature ◽  
The Self ◽  
Heat Of Reaction ◽  
Solder Reaction ◽  
Electroless Ni

The reaction mechanism between electroless Ni–P and Sn was investigated to understand the effects of Sn on solder reaction-assisted crystallization at low temperatures as well as self-crystallization of Ni–P at high temperatures. Ni3Sn4 starts to form in a solid-state reaction well before Sn melts. Heat of reaction for Ni3Sn4 was measured during the Ni–P and Sn reaction (241.2 J/g). It was found that the solder reaction not only promotes crystallization at low temperatures by forming Ni3P in the P-rich layer but also facilitates self-crystallization of Ni–P by reducing the transformation temperature and heat of crystallization. The presence of Sn reduces the self-crystallization temperature of Ni–P by about 10 °C. The heat of crystallization also decreases with an increased Sn thickness.

Effect of Cellulose Nanocrystal on Crystallization Behavior of Poly(3–hydroxybutyrate–co–3–hydroxyvalerate)

2012 ◽  
Vol 430-432 ◽  
pp. 20-23 ◽  
Author(s):  
Hou Yong Yu ◽  
Zong Yi Qin
Keyword(s):  
Heterogeneous Nucleation ◽  
Crystallization Temperature ◽  
Crystallization Behavior ◽  
Crystallization Rate ◽  
Kinetics Study ◽  
Solvent Casting ◽  
Melt Crystallization ◽  
Casting Method ◽  
Isothermal Crystallization Kinetics ◽  
Biodegradable Nanocomposites

The biodegradable nanocomposites of poly (3–hydroxybutyrate–co–3–hydroxyvalerate) (PHBV) with different cellulose nanocrystals (CNCs) contents were prepared by a solvent casting method. The effects of CNCs on the crystallization behavior of PHBV were studied by DSC. The DSC results showed that compared to PHBV, the melt crystallization temperature increased to 92.3 °C for the nanocomposites with 10 wt. % CNCs, which indicated that the crystallization of PHBV became easier with the addition of CNCs. Moreover, the non–isothermal crystallization kinetics study illustrated that overall crystallization rate of PHBV in the nanocomposites was faster than that of neat PHBV, which should be attributed to the strong heterogeneous nucleation of CNCs.

Learning the Ashby Box: an experiment in second order cybernetic modeling

Kybernetes ◽  
2019 ◽  
Vol 49 (8) ◽  
pp. 2073-2090 ◽  
Author(s):  
Andrei Cretu
Keyword(s):  
Adaptive Systems ◽  
Variable Structure ◽  
General Purpose ◽  
Black Box ◽  
Second Order ◽  
Content Type ◽  
Artificial Brain ◽  
Parallel Input ◽  
Learning And Cognition ◽  
Observer System

Purpose W. Ross Ashby’s elementary non-trivial machine, known in the cybernetic literature as the “Ashby Box,” has been described as the prototypical example of a black box system. As far as it can be ascertained from Ashby’s journal, the intended purpose of this device may have been to exemplify the environment where an “artificial brain” may operate. This paper describes the construction of an elementary observer/controller for the class of systems exemplified by the Ashby Box – variable structure black box systems with parallel input. Design/methodology/approach Starting from a formalization of the second-order assumptions implicit in the design of the Ashby Box, the observer/controller system is synthesized from the ground up, in a strictly system-theoretic setting, without recourse to disciplinary metaphors or current theories of learning and cognition, based mainly on guidance from Heinz von Foerster’s theory of self-organizing systems and W. Ross Ashby’s own insights into adaptive systems. Findings Achieving and maintaining control of the Ashby Box requires a non-trivial observer system able to use the results of its interactions with the non-trivial machine to autonomously construct, deconstruct and reconstruct its own function. The algorithm and the dynamical model of the Ashby Box observer developed in this paper define the basic specifications of a general purpose, unsupervised learning architecture able to accomplish this task. Originality/value The problem exemplified by the Ashby Box is fundamental and goes to the roots of cybernetic theory; second-order cybernetics offers an adequate foundation for the mathematical modeling of this problem.

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