scholarly journals Story of the entropy elasticity.

1986 ◽  
Vol 59 (7) ◽  
pp. 375-384
Author(s):  
MASASHI UMENO
Keyword(s):  
Entropy Elasticity

Entropy Elasticity in High Polymers

1967 ◽  
Vol 40 (3) ◽  
pp. 777-785
Author(s):  
Friedrich Linhardt
Keyword(s):  
Present Article ◽  
19Th Century ◽  
Experimental Approach ◽  
Operating Temperature ◽  
Elastic Behavior ◽  
Unusual Property ◽  
Vulcanized Rubber ◽  
Entropy Elasticity ◽  
The 19Th Century ◽  
High Polymers

Abstract Vulcanized rubber has an unusual property, known early in the 19th century, but not understood until 1935: it increases in stiffness with rise in operating temperature. A strip of rubber loaded with a weight and heated does not stretch; on the contrary, it contracts to some extent. Theoretical interpretations of this effect showed deformation of rubber, as well as its softness and high extensibility, to be determined by entropy, among other things. “Entropy elasticity” was looked upon as a peculiarity of rubber. It was thus only logical, when materials were classified as “rubbers” that they should be distinguished from all other materials by using the expression “entropy elastic behavior”. To be sure, one is inclined today to consider entropy elasticity a characteristic of all high polymers, including those not crosslinked. The present article reports an experimental approach to this problem.

Temperature Dependence of the Mechanical and Stress-Optical Behavior of Elastomers

1960 ◽  
Vol 33 (3) ◽  
pp. 763-789
Author(s):  
J. Kruse ◽  
T. Timm
Keyword(s):  
Elastic Modulus ◽  
Natural Rubber ◽  
Optical Constant ◽  
General Rule ◽  
Absolute Temperature ◽  
Double Refraction ◽  
Temperature Function ◽  
Entropy Elasticity ◽  
Optical Behavior ◽  
Valence Bonds

Abstract The temperature functions of the elastic modulus K2 and of the stress-optical constant K1 or its reciprocal 1/K1 were investigated for several elastomers. In the case of a hypothetical rubber which we have called “ideal” rubber—in analogy to gases—theory requires a direct proportionality between K2 or 1/K1 and the absolute temperature. The temperature functions of K2 and 1/K1 which we found by experiments with “real” elastomers show characteristic negative and positive deviations Δa2 and Δa1 from “ideal” values. When we put these values of Δa2 and Δa1 into a coordinate system, we find a certain orderly arrangement of the different elastomers, which allows us to picture a relationship between molecular structure and the values of Δa2 and Δa1. This brings up the possibility of explaining the experiments with the help of already known molecular-physical concepts. Although other explanations are conceivable the attempt is made to develop the simplest and most obvious ideas. It is conjectured that negative values of Δa2 and Δa1 come about from a loosening of secondary valence bonds—in certain ways, like crystal bonds— between neighboring molecules. Negative Δa1 values were found only in the crystallizable elastomers. It is further conjectured that positive values of Δa2 and Δa1 may result from the liberation by heat, of blocked, bulky molecular segments. These molecular segments can then contribute to the entropy elasticity only at higher temperatures. Positive Δa2 and Δa1 values are found chiefly in strongly crosslinked elastomers. Brief attention is given to the physical processes which are responsible for the elongation—double refraction and the entropy-elasticity. From this, it seems that the stress-optical constant and its temperature function are connected with properties of the molecular chains and on their orientability and crystallizability. The elastic modulus and its temperature function are strongly affected by the structure of the network and the molecular cohesive forces. Worthwhile hints about crystallization tendency, polarity and degree of symmetry of the different systems are given by the Δa1 and Δa2 values in the above mentioned coordinate systems. Natural rubber was tested in different recipes. The results of milling, of sulfur and accelerator additions, of time and temperature of vulcanization, on the values of K2, 1/K1, Δa2 and Δa1 were all investigated. The values of 1/K1 are at their highest level for dried latex films (unvulcanized). Milling and vulcanization, particularly the use of rather long periods and high temperatures, lower the value of 1/K1. A drop in the value of 1/K1, which regularly appears with a reduction of the negative Δa1 value, is explained as a loosening of secondary valence molecular couplings. According to this, natural rubber in the latex state is most strongly associated. According to this explanation, stretching in the unvulcanized condition is sufficient to loosen the secondary valence molecular bonds. Milling and vulcanization also act to loosen the linkages. Secondary valence bonds which are loosened by warming, as a general rule, are reestablished by prolonged cooling. It is to be supposed that the secondary valence molecular bonds under consideration are limited to small regions, somewhat comparable to the ordering in liquids. With an increasing degree of vulcanization, the Δa2 values go through a maximum which perhaps coincides with the condition of optimum vulcanization. This is explained as a maximum of the entropy-elasticity. In the case of slightly milled natural rubber which is appropriately vulcanized, the value of Δa2 can become practically zero. The change of the elastic modulus with temperature then is “ideal.” Nevertheless, no “ideal” rubber exists here, for Δa1 is less than zero.

Rubberlike entropy elasticity of a glassy alloy

2006 ◽  
Vol 89 (10) ◽  
pp. 101903 ◽  
Author(s):  
M. Fukuhara ◽  
A. Inoue ◽  
N. Nishiyama
Keyword(s):  
Glassy Alloy ◽  
Entropy Elasticity

Nonlinear Fractional Derivative Models of Viscoelastic Impact Dynamics Based on Entropy Elasticity and Generalized Maxwell Law

2010 ◽  
Vol 6 (2) ◽  
Author(s):  
Masataka Fukunaga ◽  
Nobuyuki Shimizu
Keyword(s):  
Fractional Derivative ◽  
Basic Assumption ◽  
Dynamical Behavior ◽  
Impact Dynamics ◽  
Viscoelastic Materials ◽  
Free Response ◽  
Scale Free ◽  
Collective Response ◽  
Elementary Constituent ◽  
Entropy Elasticity

Two types of models are proposed for describing nonlinear fractional derivative dynamical behavior of viscoelastic materials subject to impulse forces. The models are derived based on the thermodynamic elasticity in terms of entropy and on the “scale-free response of the material” under the basic assumption that the viscoelastic materials consist of stable coils of polymers, which we refer to as blobs. The blobs, which may be connected to each other by chemical bonds or physical bonds, are considered here as the elementary constituent of viscoelastic materials from which the nonlinear fractional derivative models are derived. Responses of individual blobs can determine the net collective response of the viscoelastic material to impulse forces. From the above consideration, two types of models are proposed in which the force elements or the stress elements are connected by the generalized Maxwell law.

Entropy elasticity in poly(2-hydroxyethyl methacrylate) gels

1977 ◽  
Vol 15 (12) ◽  
pp. 733-738
Author(s):  
K. L. Dorrington ◽  
N. G. McCrum ◽  
W. R. Watson
Keyword(s):  
Hydroxyethyl Methacrylate ◽  
Entropy Elasticity

scholarly journals Entropy elasticity of food gels certified by stress-strain relation.

1988 ◽  
Vol 54 (2) ◽  
pp. 245-248 ◽  
Author(s):  
Eiji Niwa ◽  
En-sheng Chen ◽  
Satoshi Kanoh ◽  
Teruo Nakayama
Keyword(s):  
Stress Strain ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Entropy Elasticity
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