X-Ray Investigation of the Crystallization of Vulcanized Rubber on Stretching

1948 ◽  
Vol 21 (3) ◽  
pp. 621-626 ◽  
Author(s):  
B. V. Lukin ◽  
V. I. Kasatochkin
Keyword(s):  
Tensile Strength ◽  
Crystalline Phase ◽  
Oxidative Degradation ◽  
Point Of View ◽  
Crystal Formation ◽  
Stress Strain ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Cross Links ◽  
Ray Methods

Abstract 1. x-Ray methods have been used to investigate the amount of crystalline phase in stretched samples as a function of the vulcanization time. 2. Curves relating the percentage of crystalline phase to the vulcanization time have sharply defined maxima. 3. A comparison of the curves relating tensile strength to vulcanization time with the curves of crystal formation shows their analogous character, the position of the maxima approximately corresponding to one and the same vulcanization time. 4. The position of the maxima on the curves of crystal formation is not related to the degree of stretching. 5. The effect of accelerators is to shift the maximum on the curve of crystal formation to the region of short vulcanization times and to increase the percentage of crystalline phase. 6. The curves of crystal formation and of tensile strength, and thus the behavior of the stress-strain curves for various vulcanization times, is interpreted from the point of view of the existence of two processes—the process of forming a network of cross-links by the interaction of rubber with sulfur, and the process of oxidative degradation of the rubber.

X-Ray Study of the Crystallization of Vulcanized Rubber during Stretching. II.

1951 ◽  
Vol 24 (3) ◽  
pp. 541-549 ◽  
Author(s):  
V. I. Kasotochkin ◽  
B. V. Lukin
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Crystal Formation ◽  
Oxidative Destruction ◽  
Ray Method ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Crystal Content

Abstract 1. The relation between the crystal content of stretched vulcanizates to the time of vulcanization for different mixtures of natural rubber was studied by the x-ray method. 2. It was shown that the tensile strength is a function of the crystal content of the stretched vulcanizate and of the total time of vulcanization. 3. The nature of crystal formation depends on the following factors: changes of density of the network of sulfur bridges, their distribution, the degree of oxidative destruction, and the quantity of bound sulfur which has not formed bridges between the molecular chains.

Characteristic Properties of Rubber at Low Temperatures. A Discussion of the Stress-Strain Curves of Vulcanized Rubber at Low Temperatures

1934 ◽  
Vol 7 (4) ◽  
pp. 610-617 ◽  
Author(s):  
Takeo Fujiwara ◽  
Toramatsu Tanaka
Keyword(s):  
Physical Properties ◽  
Low Temperatures ◽  
External Heat ◽  
Point Of View ◽  
Special Importance ◽  
Stress Strain ◽  
Experimental Proof ◽  
Vulcanized Rubber ◽  
The Subject ◽  
Two Phases

Abstract The hardening of rubber at low temperatures is one of the well-known physical characteristics of rubber. The loss of elasticity of raw rubber by hardening at 0° to 10° C., its turning to the consistency of glass, and its fragility at −19° C. when cooled with liquid air, and its fibering when stretched to 60–70 per cent previous to breaking, give an experimental proof of the theory of the structure of rubber molecules. Vulcanization makes raw rubber physically less sensitive to heat and to low temperatures, and is of great significance, because it enables vulcanized rubber to be used around −30° C. without losing its elasticity. The effect of external heat on the physical properties, especially on the stress-strain relations, of vulcanized rubber has been discussed mainly for temperatures from −10° to +100° C., and only two papers deal with temperatures from −30° to −60° or −70° C. (cf. Le Blanc and Kröger, Kolloid Z., 37, 205 (1925); Tener, Kingsbury and Holt, Bureau of Standards Technologic Papers Vol. 22, No. 364). Of special importance are a means of recognizing changes m the physical properties (phenomenon of freezing-hard ness) of vulcanized rubber at −30° to −60° or −70° C., and the practical value of such information. Though there is a contradiction in the fundamental meaning of the “cold resistant theory” of rubber, investigations of the two phases of the subject may throw some light on practical problems and widen the scientific point of view.

Have Mechanical Stresses Any Effect on the Oxidizability of Rubber?

1949 ◽  
Vol 22 (3) ◽  
pp. 690-698
Author(s):  
Jean Le Bras ◽  
André Salvetti
Keyword(s):  
Tensile Strength ◽  
Infrared Absorption ◽  
Vibration Frequency ◽  
Molecular State ◽  
Mechanical Stresses ◽  
Point Of View ◽  
Negative Evidence ◽  
Linear Extensions ◽  
Vulcanized Rubber ◽  
Appreciable Increase

Abstract Subjection of rubber to mechanical stresses, whether static or dynamic, does not change its inherent oxidizability, at least within the limits of stress which were applied in the experiments described. Perhaps changes would have been observed if the range of stresses had been reached where crystallization phenomena became pronounced, for sufficient distortion or change in molecular state might have a certain influence on the oxidizability. For example, Williams and Dale, in a study of infrared absorption by rubber, pointed out that linear extensions greater than 400 per cent are necessary to bring about any appreciable increase in the vibration frequency of the C — C groups. However, the elongations employed in the present work cover, in general, the range of deformations to which vulcanized rubber products are normally subjected in service; hence there seemed to be no advantage in attempting to carry out the tests under more severe conditions. From another point of view, it would appear of interest to record the following observation. In all the oxidation tests under dynamic conditions, the test-specimens broke either by being cut through near the points where they were fastened, at random points where rupture began, or when the tensile strength was lowered too much by oxidation; but in no case was actual flexcracking observed. Although this is only negative evidence, the view of Eccher that ozone is indispensable to the formation of cracking would appear to be confirmed.

Resilient Energy

1943 ◽  
Vol 16 (3) ◽  
pp. 591-608
Author(s):  
E. C. B. Bott
Keyword(s):  
Tensile Strength ◽  
Finite Differences ◽  
Practical Method ◽  
Cross Sectional Area ◽  
Point Of View ◽  
Sectional Area ◽  
Cross Sectional ◽  
Vulcanized Rubber ◽  
Reinforcing Agent ◽  
Strength Based

Abstract 1. The tensile strength of vulcanized rubber may be expressed in terms of its elongation by means of the calculus of finite differences. 2. This expression for tensile strength, based on the theoretical cross-sectional area, gives an expression for the tensile strength based on the original cross-sectional area when the former quantity is divided by the factor (E + 1), E being the elongation. 3. The expression for tensile strength based on the original cross-sectional area is integrated with respect to the elongation to give the resilient energy. 4. The trapezoidal rule has proved itself to be superior to the calculus of finite differences as a practical method of obtaining the resilient energy. 5. The total resilient energies are plotted on graphs against the percentage by volume of reinforcing agent or filler. Tangents drawn at any desired point corresponding to a certain percentage of filler give values for the partial resilient energies of base mix and of filler by the method of tangent intercepts. 6. The expressions for tensile strength are composed of one, two or three functions ; the number of functions is, in general, inversely proportional to the percentage of the filler in the vulcanizate. 7. The expressions for tensile strength and for resilient energies have no significance regarding the structure of vulcanized rubber; they have been evolved from the point of view of usefulness for evaluating compounds. 8. The values of the partial resilient energies of base mix and of filler obtained by the method of tangent intercepts have no physical meaning; they are a means of calculating the total resilient energy of a sample of vulcanized rubber.

The Effect of Solvents on the Stress-Strain Curve of Vulcanized Rubber

1930 ◽  
Vol 3 (1) ◽  
pp. 19-21 ◽  
Author(s):  
H. A. Tiltman ◽  
B. D. Porritt
Keyword(s):  
Tensile Strength ◽  
Marked Effect ◽  
Strain Curve ◽  
Theoretical Interest ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Cohesive Forces ◽  
Effect Of Solvents ◽  
Vulcanized Rubber ◽  
Permanent Effect

Abstract (1) The results indicate that the rigidity of a piece of vulcanized rubber is considerably reduced by the absorption of small amounts of a solvent; thus, at a strain of 6 ( = 600 per cent elongation) the absorption of 5 per cent by weight ( = 8 per cent by volume) of benzene lowers the rigidity by 21 per cent. (2) The greatest effect is produced by the first 20 or 30 per cent (by weight) of absorbed benzene, further absorption having a less marked effect on the stress-strain curve. (3) The absorption of solvent seems to have very little effect on the breaking elongation, although the tensile strength is considerably lowered. This conclusion, however, is probably no longer true in the case of rubber swollen by immersion in liquid, where the absorption is very much greater than in the present tests. (4) Absorption of solvent followed by complete drying appears to produce a slight, but technically negligible, permanent effect on the stress-strain curve. It is evident from these results that when it is necessary to use solvents, either in the process of manufacture or the after-treatment of rubber products, these should be selected as free as possible from high-boiling constituents liable to be permanently retained by the rubber with consequent detriment to its strength. A conclusion of some theoretical interest is that since all the stresses in the present investigation were calculated on the dimensions of the original dry rubber, the low rigidity of swollen rubber cannot be ascribed simply to the “dilution” of the rubber by the absorbed liquid, but must be due to a loosening of the cohesive forces between the ultimate particles of the material.

Morphology, rheology and biodegradation of oxo-degradable polypropylene/polylactide blends

2018 ◽  
Vol 38 (3) ◽  
pp. 239-249 ◽  
Author(s):  
Dev K. Mandal ◽  
Haripada Bhunia ◽  
Pramod K. Bajpai ◽  
Chandrasekhar V. Chaudhari ◽  
Kumar A. Dubey ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Tensile Strength ◽  
Point Of View ◽  
Calcium Stearate ◽  
Melt Blending ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Biodegradability Test ◽  
Scanning Electron

AbstractThe blends of polypropylene (PP)/polylactide (PLA) with or without compatibilizer, and with pro-oxidant (cobalt stearate/calcium stearate) and pro-oxidant filled PP were prepared by using the melt blending technique. Films of these blends were prepared by compression molding. PP85PL15 and PP85PL15MA4 were the optimum blends from the tensile strength point of view. The improvement in the tensile strength of PP85PL15MA4 blend was achieved by addition of 4 phr compatibilizer. Cobalt stearate and calcium stearate were added separately to PP85PL15MA4 blend in 0.2% (w/w) ratio. The optimized blends were further characterized by differential scanning calorimetry, X-ray diffraction, rheological studies, scanning electron microscopy (SEM) and biodegradability test. Rheological studies confirmed the pseudo-plastic nature of all the blend samples. SEM studies have revealed that the addition of PLA in PP85PL15 enhances the void and roughness on the blend. All the prepared blends have biodegraded in the composting environment and the blend containing pro-oxidant biodegraded to the maximum extent.

The Crystal Structure of Rubber Hydrochloride

1943 ◽  
Vol 16 (4) ◽  
pp. 848-856
Author(s):  
C. W. Bunn ◽  
E. V. Garner
Keyword(s):  
Crystal Structure ◽  
Physical Properties ◽  
Carbon Chain ◽  
Point Of View ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carbon Compounds ◽  
Ray Methods ◽  
Temperature Melting

Abstract “Rubber hydrochloride”, the crystalline substances made by addition of hydrogen chloride to rubber, is of interest for two reasons. First, the periodicity along the fibre axis of drawn specimens indicates that the carbon chain has not the simple plane zigzag form found in paraffin hydrocarbons, but is somewhat shortened by folding. There is similar evidence that several other chain polymers also have folded chains; the elucidation of the geometry of such molecules would form a useful contribution to our knowledge of the stereochemistry of carbon compounds in general and chain polymers in particular. Rubber hydrochloride appeared to be a suitable substance for crystallographic investigation from this point of view: it gives a well-defined x-ray diffraction pattern. Moreover, a prediction of the chain form has been made on the basis of a knowledge of the periodicity and the use of a hypothesis which has been called the principle of staggered bonds. The determination of the structure by x-ray methods forms the first test of the validity and usefulness of this hypothesis. Secondly, rubber hydrochloride is interesting on account of its physical properties. Unlike rubber itself, it is crystalline at room temperature, “melting” at about 115° C. The present work on its crystal structure forms part of a program of research being carried out in this laboratory, and is a contribution to the attempt to understand the physical properties of chain polymers in terms of molecular structure.

The Proportion of Crystalline and Amorphous Components in Stretched Vulcanized Rubber

1946 ◽  
Vol 19 (4) ◽  
pp. 1124-1136
Author(s):  
A. J. Wildschut
Keyword(s):  
Tensile Strength ◽  
Amorphous Phase ◽  
Distance Function ◽  
Close Agreement ◽  
Crystalline Material ◽  
Temperature Relation ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Equal Importance

Abstract Determinations of the tension-temperature relation of stretched vulcanized rubber can provide us with data about the proportion of crystalline and amorphous components. The amount of crystalline material appears to be 30–32 per cent at 600 per cent elongation and at 20° C. An expression is derived relating percentage of crystalline material and temperature. The results are in close agreement with those of x-ray measurements carried out by Goppel, but diverge largely from those obtained by Field. The cause of this difference is not yet clear. Stretched vulcanized rubber consists of a predominating amorphous phase, with crystallites embedded in it. On stretching orientation occurs, and a systematic addition of secondary valency forces is possible. This is the main cause of the existence of a certain tensile strength. Crystallization, though important as an indication on orientation, is more or less an incidental phenomenon. The distance function of the secondary forces may be of equal importance with the orientation.

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