Changes of Fatigue Resistance of Vulcanized Natural Rubbers during Swelling

1953 ◽  
Vol 26 (1) ◽  
pp. 70-77 ◽  
Author(s):  
V. E. Gul ◽  
T. V. Dorokhina ◽  
B. A. Dogadkin
Keyword(s):  
Energy Loss ◽  
Natural Rubber ◽  
Fatigue Resistance ◽  
Modulus Of Elasticity ◽  
Dibutyl Phthalate ◽  
Relative Elongation ◽  
Chemical Processes ◽  
Initial Increase ◽  
Degree Of Swelling ◽  
Swollen Vulcanizates

Abstract A method of fatiguing swollen vulcanizates of natural rubber while maintaining a minimum deforming load, independent of the change of modulus of elasticity of the experimental specimens, was devised. The effect of swelling vulcanized natural rubber in petrolatum and in dibutyl phthalate on fatigue resistance was studied. With increase of swelling of a vulcanizate in dibutyl phthalate and in petrolatum, an initial increase of fatigue resistance was observed up to 1.8 times the fatigue resistance of the unswollen vulcanizate. Following this, a decrease of fatigue resistance was observed. The equation obtained for the change of fatigue resistance as a function of the degree of swelling is explained by two simultaneous processes: (1) increase of fatigue resistance because of decrease of energy loss in the destructionof intermolecular bonds, and (2) initiation of chemical processes leading to destruction, and a smaller difference between the deformation and the relative elongation at rupture. The effect of the character of the solvent used for swelling on the nature of the fatigue resistance-swelling relation is shown.

Investigation of the Role of Intermolecular Forces in the Mechanism of High-Elastic Deformation. VII. The Effect of Molecular Interaction on the Fatigue Resistance of High Polymers Having Highly Developed Spatial Structures

1954 ◽  
Vol 27 (2) ◽  
pp. 363-373
Author(s):  
V. E. Gul ◽  
D. L. Fedyukin ◽  
B. A. Dogadkin
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Fatigue Resistance ◽  
Dibutyl Phthalate ◽  
Intermolecular Forces ◽  
Spatial Structures ◽  
Paraffin Oil ◽  
Degree Of Swelling ◽  
Natural Rubber Vulcanizates

Abstract It is shown experimentally that an irregular change of the fatigue resistance of loaded natural-rubber vulcanizates with increase of the degree of swelling in paraffin oil and in dibutyl phthalate is caused by the superposition of two processes: the increase of fatigue resistance, as a result of the reduction of mechanical losses, and the decrease of fatigue resistance due to the decrease of tensile strength proportional to the higher degree of swelling.

Phenothiazine as an Antifatigue Agent for Natural Rubber, Synthetic Polyisoprene and SBR

1965 ◽  
Vol 38 (3) ◽  
pp. 661-665
Author(s):  
Z. N. Tarasova ◽  
I. I. Eitingon ◽  
L. G. Senatorskaya ◽  
T. V. Fedorova ◽  
B. A. Dogadkin
Keyword(s):  
Mechanical Properties ◽  
Synergistic Effect ◽  
Natural Rubber ◽  
Thermal Oxidation ◽  
Fatigue Resistance

Abstract Phenothiazine has no effect on vulcanization of rubber or standard mechanical properties of the vulcanizates. Phenothiazine considerably increases fatigue resistance of vulcanizates of the rubbers studied, under different fatigue conditions. Under the effect of thermal oxidation and repeated deformation phenothiazine or its conversion products combine with the vulcanizate. The phenothiazine does not combine when subjected only to heating. When used with certain inhibitors of oxidation phenothiazine has a synergistic effect.

Thermoplastic Natural Rubber of Co-Polyamide: Effect of Blend Ratios on Mechanical, Swelling, Dynamic and Morphological Properties

2013 ◽  
Vol 844 ◽  
pp. 89-92
Author(s):  
Boripat Sripornsawat ◽  
Azizon Kaesaman ◽  
Charoen Nakason
Keyword(s):  
Natural Rubber ◽  
Dynamic Properties ◽  
Complex Viscosity ◽  
Continuous Phase ◽  
Morphological Properties ◽  
Elongation At Break ◽  
Degree Of Swelling ◽  
Tan Δ ◽  
Thermoplastic Natural Rubber ◽  
Blend Ratios

Maleated natural rubber (MNR) was synthesized and formulated to prepare thermoplastic natural rubber (TPNR) by blending with co-polyamide (COPA). It was found that 100% modulus, tensile strength, elongation at break, hardness and degree of swelling increased with increasing proportion of COPA. However, degree of swelling and tension set value decreased which reflects enhancing of rubber elasticity. Dynamic properties were also determined by a rotor less oscillating shear rheometer (Rheo Tech MDpt). It was found that increasing proportion of MNR caused increasing of storage modulus and complex viscosity but decreasing tan δ value. Morphological properties were also determined by SEM technique. It was found that the MNR/COPA simple blends with the proportion of rubber 40, 50 and 60 wt% exhibited the co-continuous phase structures.

Estimation, from Swelling, of the Structural Contribution of Chemical Reactions to the Vulcanization of Natural Rubber. Part II. Estimation of Equilibrium Degree of Swelling

1964 ◽  
Vol 37 (2) ◽  
pp. 571-575 ◽  
Author(s):  
Bryan Ellis ◽  
G. N. Welding
Keyword(s):  
Natural Rubber ◽  
Chemical Reactions ◽  
Volume Fraction ◽  
Equilibrium Degree ◽  
Degree Of Swelling ◽  
Rubber Part ◽  
Structural Contribution

Abstract An investigation has been made of the measurement of degree of swelling of vulcanizates and the estimation of υτ, the volume fraction of polymer in a vulcanizate swollen to equilibrium. Methods have been established for dealing with a volatile swelling liquid, allowing for small percentages of nonpolymer in the vulcanizates, testing for diffusion equilibrium and correcting for swelling increment. The resulting values of υτ are suitable for use as described in the preceding Part I.

Solubility of Sulfur and Dithiocarbamates in Natural Rubber

1995 ◽  
Vol 68 (5) ◽  
pp. 794-803 ◽  
Author(s):  
M. D. Morris ◽  
A. G. Thomas
Keyword(s):  
Natural Rubber ◽  
Experimental Method ◽  
Interaction Parameter ◽  
Reliable Data ◽  
Experimental Results ◽  
Heat Of Fusion ◽  
Latent Heat Of Fusion ◽  
Degree Of Swelling ◽  
Zinc Diethyldithiocarbamate ◽  
Adequate Method

Abstract Knowledge of equilibrium solubilities of sulfur and accelerators in rubbers at various temperatures allows prediction of whether blooming is possible in particular compounds or products. Reliable data of this nature for natural rubber appeared not to exist in the literature. Immersion of 1 mm thick sheets of peroxide-vulcanized natural rubber in both liquid and, more surprisingly, powdered solid curatives was found to be an adequate method for measuring solubilities. The same experimental method also enabled some diffusion data to be obtained. Solubilities of sulfur, zinc diethyldithiocarbamate (ZDEC) and zinc di-n-butyl dithiocarbamate (ZDBC) were determined at various temperatures between 23° and 135°C. The experimental results did not agree well with the theory which had previously been found to describe the solubility of waxes in natural rubber. This theory, which is a combination of the Flory-Huggins Equation with an expression for the latent heat of fusion, was modified to take into account the dependence of the interaction parameter on temperature and on degree of swelling. The new expression gave much better agreement with the experimental results for all three substances.

Fatigue Resistance of Natural Rubber in Compression

1982 ◽  
Vol 55 (2) ◽  
pp. 337-351 ◽  
Author(s):  
P. B. Lindley ◽  
A. Stevenson
Keyword(s):  
Natural Rubber ◽  
Fatigue Resistance ◽  
Strain Energy ◽  
Strain Energy Release ◽  
Maximum Tensile Stress ◽  
Maximum Deformation ◽  
Energy Release Rates ◽  
Strain Energy Release Rates ◽  
Crack Growth Rates

Abstract Repeated deformation of natural rubber cylinders in compression causes cracks to initiate at points of maximum tensile stress concentration (e.g., at bond edges). These cracks grow until all the rubber which at the maximum deformation bulges outside the original profile of the cylinder is removed. Crack growth rates (da/dN) and strain energy release rates (G) have been determined. G is substantially independent of crack length. The relation between da/dN and G appears to be a fundamental material property for use in the determination of fatigue lives. Shaping the force free surface improves fatigue resistance.

Investigations in the Field of Rubber Vulcanization. IV. Phenomenon of Vulcanization Optimum in Mixtures with a Large Proportion of Constructive Agent

1950 ◽  
Vol 23 (1) ◽  
pp. 1-8
Author(s):  
B. Dogadkin ◽  
B. Karmin
Keyword(s):  
Natural Rubber ◽  
Crystalline Phase ◽  
Relative Elongation ◽  
Kinetic Curve ◽  
Butadiene Rubber ◽  
Kinetic Curves ◽  
Preceding Paragraph ◽  
Destructive Processes ◽  
Natural Rubber Vulcanizates ◽  
Small Content

Abstract 1. In mixtures with a large content of constructive (vulcanizing) agent, the vulcanization-optimum phenomenon is connected with the formation of dense space-lattices in the structure of the vulcanizate, which inhibit the formation of crystalline or highly oriented segments during elongation. 2. In contrast to mixtures with a small content of vulcanization agent, the vulcanization optimum of which is explained by superimposition of oppositely directed constructive and destructive processes, the case noted in the preceding paragraph shows a maximum only on the kinetic curve representing the change in strength. The kinetic curves representing relative elongation, swelling, and solubility are monotonic in character. 3. The maximum on the kinetic curve representing the change in strength in mixtures with a large content of constructive agent occurs before complete combination of the latter with the rubber. 4. In consequence of the absence of oppositely directed actions on the part of sulfur and oxygen, the vulcanization of sodium-butadiene rubber mixtures shows a maximum only on the kinetic curves representing the change in strength. 5. The position of the strength maximum in mixtures with a large content of constructive agent depends on the rate of deformation. As the rate of deformation is decreased, the maximum appears after more prolonged vulcanization periods of the mixtures. 6. The strength of natural rubber vulcanizates at the vulcanization optimum is a linear function of the quantity of crystalline phase formed during elongation.

scholarly journals The chemistry of daytime sprite streamers – a model study

2013 ◽  
Vol 13 (11) ◽  
pp. 29521-29550
Author(s):  
H. Winkler ◽  
J. Notholt
Keyword(s):  
Atomic Oxygen ◽  
Chemical Processes ◽  
Electric Breakdown ◽  
Initial Increase ◽  
Altitude Range ◽  
Ozone Destruction ◽  
Model Study ◽  
Catalytic Ozone Destruction ◽  
Catalytic Ozone ◽  
Breakdown Event

Abstract. The chemical processes in daytime sprite streamers in the altitude range of 30–54 km are investigated by means of a detailed ion-neutral chemistry model (without consideration of transport). The model results indicate that ozone perturbations due to daytime sprites streamers differ considerably from the ones of nighttime events. Due to liberation of atomic oxygen there is an initial increase of ozone. In terms of relative ozone change, this effect decreases with altitude. While for nighttime conditions, reactive nitrogen produced during the electric breakdown is converted into less reactive NO2, in the sunlit atmosphere NOx causes catalytic ozone destruction. As a consequence, there is significant ozone loss in sprite streamers in the daytime atmosphere, in particular at higher altitudes. At an altitude of 54 km, ozone in the streamer column has decreased by about 15% fifteen minutes after the breakdown event.

Preparation, fracture, and fatigue of exfoliated graphene oxide/natural rubber composites

RSC Advances ◽  
2015 ◽  
Vol 5 (22) ◽  
pp. 17140-17148 ◽  
Author(s):  
Bin Dong ◽  
Chang Liu ◽  
Liqun Zhang ◽  
Youping Wu
Keyword(s):  
Graphene Oxide ◽  
Natural Rubber ◽  
Fatigue Resistance ◽  
Rubber Composites ◽  
Exfoliated Graphene ◽  
Natural Rubber Composites

The fracture and fatigue resistance of graphene oxide reinforced natural rubber composites which were prepared by latex co-coagulation was investigated.

Changes of Electrical Resistance of Rubbers Loaded with Carbon Black

1957 ◽  
Vol 30 (2) ◽  
pp. 572-583
Author(s):  
D. G. Marshall
Keyword(s):  
Experimental Investigation ◽  
Carbon Black ◽  
Natural Rubber ◽  
Electrical Resistance ◽  
Current Flow ◽  
Electrical Contact ◽  
Butyl Rubber ◽  
Initial Increase ◽  
Electrically Conducting ◽  
Conducting Rubber

Abstract Many workers have studied the changes in resistivity that occur on deforming rubbers loaded with carbon black. This paper describes three types of experimental investigation that do not seem to have received detailed study previously, and also a theory that explains the results qualitatively in terms of variations of contact resistances between carbon black particles. Firstly, the changes of resistance of vulcanized natural rubber, Butyl rubber, Neoprene, and Thiokol FA loaded with carbon black have been studied during cyclic deformations. Secondly, the initial increase of resistance during stretching testpieces of vulcanized natural rubber containing several loadings of different carbon blacks has been investigated. Finally, the changes of resistance with time that occur after stretching and releasing samples of electrically conducting rubber have been studied. The ingredients and preparation of the compounds used in experiments discussed in this paper are listed in the Appendix. The testpieces used in the following experiments were approximately 0.7 cm. wide, 0.1 cm. thick, and 7.0 cm. long. Electrical contact was established by means of brass strips bonded by molding into the ends of the samples, so that the direction of current flow was along the length of the pieces, and in the same direction as the extensions.

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