Forced and Spontaneous Changes in the Arrangement of the Molecules in Stretched Rubber. Crystals and Fused Phase in Stretched Rubber

1939 ◽  
Vol 12 (4) ◽  
pp. 736-754 ◽  
Author(s):  
P. A. Thiessen ◽  
W. Wittstadt
Keyword(s):  
Natural Rubber ◽  
Mechanical Stress ◽  
Mechanical Deformation ◽  
Unsaturated Hydrocarbon ◽  
X Rays ◽  
Double Refraction ◽  
Amorphous Substance ◽  
X Ray ◽  
Space Lattice ◽  
Differences Of Opinion

Abstract An unsaturated hydrocarbon of the formula (C5H8)2x is the basis of natural rubber. Although there are still differences of opinion about the size of the molecules, it may nevertheless be accepted as fairly certain that the parent substance, the unsaturated hydrocarbon, is composed of a mixture of various steps of polymerization. At ordinary temperatures and under no mechanical stress, both vulcanized and unvulcanized rubber are isotropic glasses. Exposed to x-rays they give the diagram of an amorphous substance, i.e., a broad, diffuse ring. As a result of mechanical deformation, especially stretching, rubber becomes anisotropic. This anisotropy is manifest by the appearance of optical double refraction, as well as by an x-ray fiber diagram, which replaces the amorphous ring. This indicates orientation of the molecules and rearrangement into a space lattice, measurements of which have been made repeatedly and which make probable a rhombic structure.

Crystals and Fused Substance in Stretched Rubber. (A Preliminary Communication)

1936 ◽  
Vol 9 (1) ◽  
pp. 52-54
Author(s):  
Peter A. Thiessen ◽  
Werner Wittstadt
Keyword(s):  
Natural Rubber ◽  
Mechanical Stress ◽  
Permanent Deformation ◽  
Unsaturated Hydrocarbon ◽  
Final State ◽  
Double Refraction ◽  
Space Lattice ◽  
Temperature Range ◽  
Vulcanized Rubber ◽  
Wide Range

Abstract When rubber is stretched, the arrangement of the molecules in the space lattice does not come to an end when the elongation is terminated, but continues for a certain time afterward. The final state of orientation for any elongation depends upon the temperature in the sense that within a wide temperature range there is at each temperature a definite ratio between the quantity of crystallized substance and the glass-like fused component. Within this temperature range, the proportion of crystallized substance diminishes with increase in temperature. This change is reversible, and the equilibrium is greatly influenced by the pressure. It may be considered as an established fact today that natural rubber is essentially a mixture of various polymers of an unsaturated hydrocarbon. At ordinary temperatures and in the absence of mechanical stress, it is an isotropic glass, both in the raw and vulcanized states. When deformed mechanically, particularly when stretched, it becomes anisotropic, a change which is evidenced by the appearance of an optical double refraction and an x-ray fiber diagram. This phenomenon is attributable to an orientation of the molecules in the direction of stretching and their arrangement into a space lattice which can be measured and defined accurately. The increase in double refraction as well as the clearness of the reflection interference pattern in the Roentgen diagram is proportional to the degree of elongation of both raw and vulcanized rubber, and it is reversible after a certain time of relaxation. In natural rubber, the reversibility of the phenomenon is disturbed by flow phenomena, which upon prolonged mechanical stress lead to permanent deformation. In well vulcanized rubber these phenomena are of little significance over a wide range of temperatures.

scholarly journals A Method to Optimize the Electron Spectrum for Simulating Thermo-Mechanical Response to X-ray Radiation

Symmetry ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 59
Author(s):  
Xianwen Ran ◽  
Bo Wang ◽  
Kun Zhang ◽  
Wenhui Tang
Keyword(s):  
Electron Spectrum ◽  
Mechanical Response ◽  
Least Squares Method ◽  
Mechanical Deformation ◽  
X Rays ◽  
Linear Least Squares ◽  
X Ray ◽  
Relativistic Electron Beams ◽  
Transport Code ◽  
The Difference

The X-ray pulse originating from high altitude nuclear detonation (HAND) is mainly soft X-ray and its intensity is high enough to gasify the penetrated material and then lead to the severe thermo-mechanical deformation of unpenetrated material from the gasified blow-off effect. This effect cannot be directly reproduced in a lab for the lack of the X-ray source like HAND. At present, the low-energy relativistic electron beams resulting from an electron accelerator are usually used to approximately reproduce this effect, but the difference in the energy-deposited profile in materials between the electron and X-ray cannot be eliminated. In this paper, the symmetric linear least squares method was used to optimize the electron spectrum, and the general Monte Carlo N-Particle Transport Code calculations showed the optimized spectrum can produce the same energy-deposited profile in aluminum, copper, and tantalum with the soft X-rays like 1 keV or 3 keV spectrums. This indicates that it is possible to simulate the severe thermo-mechanical deformation resulting from HAND using the optimized electron spectrums.

The Rubber-like Behavior of an Artificial Substance (Oppanol) when Irradiated with X-rays

1938 ◽  
Vol 11 (4) ◽  
pp. 687-688
Author(s):  
R. Brill ◽  
F. Halle
Keyword(s):  
Natural Rubber ◽  
Normal State ◽  
X Rays ◽  
Organic Substances ◽  
Chain Molecules ◽  
X Ray ◽  
Natural Substances ◽  
Amorphous Sulfur ◽  
Definite Temperature ◽  
Long Chain

Abstract As is known, natural rubber has the property of giving, when stretched, an x-ray fiber diagram, whereas in a normal state the same rubber is amorphous. Numerous other natural substances such as hair and tendon, and artificial substances such as polychloroprene, behave in the same way. However, this effect is not confined to purely organic substances, and it is to be found, for example, in the case of so-called amorphous sulfur and polyphosphornitryl chloride (PNCl2)x. All these substances have the property in common with one another of exhibiting a rubber-like elasticity within a definite temperature range, and of being composed of long-chain molecules.

The Degree of Crystallinity in Natural Rubber. III. Correlation between X-Ray and Density Measurements

1950 ◽  
Vol 23 (2) ◽  
pp. 306-310 ◽  
Author(s):  
J. J. Arlman
Keyword(s):  
Natural Rubber ◽  
Unit Cell ◽  
Degree Of Crystallinity ◽  
X Rays ◽  
Density Measurements ◽  
X Ray ◽  
Degree Of Crystallization ◽  
The Degree Of Crystallinity

Abstract In 1925 Katz discovered the crystallization of stretched rubber. In the following years several investigators tried to determine the structure of rubber crystallites. The densities of the rubber crystallites calculated from the results of these investigations varied strongly. The results of x-ray and density measurements on crude rubber carried out by the author can be made to correspond only when the latter are based on the unit cell of Bunn. It is shown by experiment that, to measure the correct degree of crystallization, it is necessary to use monochromatic x-rays.

The Crystallization of Weakly Vulcanized Rubber by Pressure

1940 ◽  
Vol 13 (1) ◽  
pp. 48-48 ◽  
Author(s):  
P. A. Thiessen ◽  
W. Kirch
Keyword(s):  
Melting Point ◽  
Natural Rubber ◽  
Crystalline Phase ◽  
Normal Pressure ◽  
Latex Film ◽  
X Rays ◽  
Amorphous Substance ◽  
Temperature Range ◽  
Vulcanized Rubber

Abstract Crystallization can be brought about in weakly vulcanized rubber by the method described by Thiessen and Kirsch for natural rubber. When samples of this type of vulcanized rubber were exposed to x-rays below + 6° C, but not under pressure, then Debye-Scherrer diagrams corresponding to those of a crystallized latex film were obtained. To determine the influence of pressure on these vulcanizates, samples were subjected to pressure on all sides in the chambers of the pressure apparatus described in the earlier work. After having been exposed for 100 days the sample which had been kept at + 6° C under 30 atmospheres' pressure showed a very marked Debye-Scherrer diagram, whereas samples kept at the same temperature but at normal pressure showed only the halo of an amorphous substance. Consequently pressure has an influence on the crystallization of vulcanized rubber as well as of raw rubber. The melting point of the crystalline phase lies between + 11° C. and +13° C. Obviously then an increase in pressure raises the temperature range of supercooling.

Synchrotron Radiation X-Ray Scattering Techniques for Studying the Micro- and Nanostructure of Wood and their Relation to the Mechanical Properties

2008 ◽  
Vol 599 ◽  
pp. 107-125 ◽  
Author(s):  
Martin Müller
Keyword(s):  
Cell Wall ◽  
Synchrotron Radiation ◽  
Mechanical Stress ◽  
Structural Changes ◽  
Structural Parameters ◽  
Cellulose Microfibrils ◽  
X Rays ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

X-ray scattering techniques have been a very useful tool for the non-destructive analysis of the wood structure. X-rays are sensitive to structural parameters such as the composite structure of wood cell walls, the crystal structure of cellulose microfibrils and their helical arrangement in the cell wall, which is usually described by the microfibril angle (MFA). With the availability of synchrotron radiation sources novel experiments on wood have become possible. The increased flux of X-rays makes the in situ and time-resolved investigation of structural changes upon mechanical stress possible. The low-divergence synchrotron radiation X-rays can be focused down to sub-micrometer size, enabling scanning studies of the wood nanostructure with (sub-)microscopic position resolution. This chapter highlights very recent advances in the understanding of wood micro- and nanostructure, which were only possible using synchrotron radiation. Examples include the MFA determination in the individual layers of the secondary cell wall, the imaging of the helical structure of the cellulose microfibrils in the cell wall, lattice strain as induced by applied mechanical stress and the structural changes of different wood types under external tensile stress.

scholarly journals On the interpretation of the indications of atomic structure presented by crystals when interposed in the path of X-rays

1914 ◽  
Vol 91 (623) ◽  
pp. 1-16 ◽  
Keyword(s):  
Regular Point ◽  
Lower Class ◽  
Trigonal Axis ◽  
Point System ◽  
X Rays ◽  
Simple Modification ◽  
Cubic Symmetry ◽  
X Ray ◽  
Space Lattice ◽  
Three Space

W. L. Bragg states in his exposition of the method of investigating the structure of crystals by means of X-rays, that a slight symmetrical distortion of the arrangement of the atoms, which would reduce the crystal symmetry, would not affect any of the results that he had just been describing. Advancing considerably beyond this conclusion, it is proposed to show that a large amount of a certain kind of deformation of an atomic system arranged according to either of the three space-lattices possessing cubic symmetry, considerable enough to profoundly alter the nature of the arrangement, can take place with out any appreciable evidence of this deformation being presented by the X-ray results. The argument consists of the proofs of the following propositions:— Proposition 1.—Each of the three space-lattices which posses cubic symmetry can, by a simple modification, be converted into a regular point-system having this symmetry, but the system of trigonal axes of which, unlike that of the space-lattice, is of non-intersecting kind. The method employed to effect this modification is to so select one-fourth of the trigonal axes of the space-lattice concerned that no two of the selected axes intersect, and then to destroy the remaining three-fourths by symmetrically shifting each point of the space-lattice to the same extent in the appropriate direction along the selected trigonal axis on which it lies, and consequently away from the three other trigonal axes which passed through it. In the cases of the cubic space-lattice and the cube-centred space-lattice, the shifts, can take place in both directions on an axis or in one only. The effect of axes continues to be a trigonal axis of the system of points is that each of the selected axes continues to be a trigonal axis of the system of points, while each of the remaining three-fourths of the trigonal axes ceases to be so. The system of points resulting has cubic symmetry, but in nearly all the cases this is of a lower class than that of the space-lattice from which it is derived.

An X-Ray Study of Some Synthetic Elastomers. Polychloroprenes

1946 ◽  
Vol 19 (4) ◽  
pp. 1088-1089
Author(s):  
Henri Fournier ◽  
Jean Jacques Trillat
Keyword(s):  
Natural Rubber ◽  
X Rays ◽  
Trans Form ◽  
Unsaturated Hydrocarbons ◽  
Preliminary Heating ◽  
X Ray ◽  
Orientation Process ◽  
Identity Period

Abstract Synthetic rubbers prepared from isoprene and other unsaturated hydrocarbons have been studied by means of x-rays by various investigators, including Carothers, Katz, Meyer, and Sebrell and Dinsmore. In general, these synthetic products differ markedly from natural rubber in that when they are stretched, they do not give any fibre diagrams. On the contrary, μ-polychloroprene (Neoprene), H2C:CC·CH:CH2, when stretched to about 500 per cent, gives a somewhat diffused fibre diagram with an identity period of 4.8 A˚.U., corresponding to the length of a chloroprene unit in the trans form. We have verified this fact, and have found, in addition, that preliminary heating of the polychloroprene facilitates this orientation process which takes place upon stretching. The investigation was continued by a study of a product which had not previously been studied, viz., chloroisoprene:

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

Chemical Species Identification in an SEM by Changes in Emitted X-Ray Energies

1974 ◽  
Vol 32 ◽  
pp. 570-571
Author(s):  
R. H. Duff
Keyword(s):  
Species Identification ◽  
Valence Electron ◽  
Chemical Species ◽  
X Rays ◽  
Chemical Bonds ◽  
Small Shift ◽  
X Ray ◽  
Electron Transitions ◽  
Peak Energy ◽  
Chemical Combination

A material irradiated with electrons emits x-rays having energies characteristic of the elements present. Chemical combination between elements results in a small shift of the peak energies of these characteristic x-rays because chemical bonds between different elements have different energies. The energy differences of the characteristic x-rays resulting from valence electron transitions can be used to identify the chemical species present and to obtain information about the chemical bond itself. Although these peak-energy shifts have been well known for a number of years, their use for chemical-species identification in small volumes of material was not realized until the development of the electron microprobe.

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