scholarly journals Dynamic stress relaxation in carbon black filled vulcanizates.

1986 ◽  
Vol 59 (5) ◽  
pp. 282-289
Author(s):  
Kunihiko FUJIMOTO ◽  
Hidehiko AKIMOTO
Keyword(s):  
Stress Relaxation ◽  
Carbon Black ◽  
Dynamic Stress

Longitudinal Cracking in a Carbon Black Filled Natural Rubber Vulcanizate during Chemical Stress Relaxation

1998 ◽  
Vol 71 (2) ◽  
pp. 157-167 ◽  
Author(s):  
G. R. Hamed ◽  
J. Zhao
Keyword(s):  
Stress Relaxation ◽  
Carbon Black ◽  
Natural Rubber ◽  
Longitudinal Crack ◽  
Chemical Stress ◽  
Loading Direction ◽  
Rubber Vulcanizate ◽  
Edge Cracks ◽  
Forced Air ◽  
Oxidative Attack

Abstract Thin specimens of a black-filled, natural rubber vulcanizate have been held in uniaxial tension at 72°C and 200% elongation in a forced air oven. After substantial oxidative attack (inferred from stress relaxation), small edge cracks formed. Initially, these cracks grew perpendicular to the loading direction, but, upon reaching about 0.1 mm in depth, longitudinal crack growth commenced and fracture progressed by a kind of 0°-peel process with “splitting-off” of successive strands of rubber. This phenomenon is attributed to anisotropy in strength caused both by straining and by oxidative attack.

Differential Dynamic Shear Moduli of Carbon Black-Filled Styrene-Butadiene Rubber Subjected to Large Shear Strain Histories

1986 ◽  
Vol 59 (2) ◽  
pp. 241-254 ◽  
Author(s):  
Koichi Arai ◽  
John D. Ferry
Keyword(s):  
Stress Relaxation ◽  
Carbon Black ◽  
Shear Strain ◽  
Single Step ◽  
Fourth Power ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Initial Value ◽  
Shear Moduli ◽  
Styrene Butadiene

Abstract Combined measurements of shear-stress relaxation and differential dynamic storage and loss shear moduli G′ and G″ following a single-step shear strain of 0.4, as well as measurements of dynamic moduli in on-off strain and stress histories, have been made on styrene-butadiene rubber (type 1502) filled with carbon black (N299) at loadings of 40, 50, 60, and 70 phr, with 10 phr Sundex 790 oil. Both cured and uncured compounds were studied at temperatures of 25.0° and −0.5°C respectively. The maximum oscillatory shear strain was 0.005, and the frequency was from 0.4 to 1.8 Hz. The storage shear modulus G′(ω, 0) measured without imposition of static strain was approximately proportional to the fourth power of the volume fraction of black. With imposition of single-step strain, the differential storage modulus G′(ω, γ; t) fell 25% to 35% but slowly recovered somewhat while the strain was maintained for 4 to 5 h. During this period, the static stress relaxed continuously. At the highest content of black, the drop in log G′ was the least, and the final recovery was closest to the initial value of G′(ω, 0). In on-off experiments on uncured compounds, when the strain was “on” for 250 s and then “off” (either stress or strain returned to zero), G′ decreased when the strain was imposed as before and decreased further when it was removed. In the “off” state, G′ recovered partially but did not attain the initial value of G′(ω, 0) even after 7 d. In on-off experiments on cured compounds, removal of stress caused G′ to either increase or decrease depending on the content of black; in any case, in the “off” state, G′ recovered completely to its initial value. Other strain histories involved on-off sequences with different “on” periods and multiple on-off sequences with different “on” periods and multiple on-off sequences. The results are interpreted in terms of a network of black particle aggregates whose contacts can slowly rearrange even in the absence of stress as shown by stress relaxation at very small strains in earlier studies. In large strains, it is postulated that some contacts are broken but can partially reform, especially in the stress-free state; the rate of reformation is similar to that of small-strain stress relaxation. Only in cured compounds is the network fully recovered, presumably because in these the particles are imbedded in a crosslinked matrix and have crosslinked bridges that facilitate reestablishment of interparticle contacts, whereas in uncured compounds the matrix has no crosslinks and the bound rubber on adjacent particles may be merely entangled.

Stress relaxation in carbon-black-filled rubber vulcanizates at moderate strains

Polymer ◽  
1984 ◽  
Vol 25 (4) ◽  
pp. 559-568 ◽  
Author(s):  
C.I. MacKenzie ◽  
J. Scanlan
Keyword(s):  
Stress Relaxation ◽  
Carbon Black ◽  
Filled Rubber

Test of Dynamic Strength Characteristics of Lishi Loess

2013 ◽  
Vol 303-306 ◽  
pp. 2902-2907 ◽  
Author(s):  
Nian Qin Wang ◽  
Xiao Ling Liu ◽  
Bo Han ◽  
Bo Tao Liu
Keyword(s):  
Stress Relaxation ◽  
Dynamic Stress ◽  
Peak Stress ◽  
Confining Pressure ◽  
Dynamic Strain ◽  
Soil Consolidation ◽  
Strength Parameters ◽  
Loading Test ◽  
Loess Slope ◽  
Effective Strength

Lishi loess is an important component of loess slope. To explore the structure and strength change characteristics of Lishi loess caused by shock (vibration) action, and to reveal the mechanism of loess slope catastrophe, the dynamic triaxial test was performed by using equivalent sine wave under strain controlling. The results show that:① There is an obvious stress relaxation phenomenon during the same cyclic loading test, the degree decreases with the increasing of dynamic strain and confining pressure. And the influence of dynamic strain variation on stress relaxation degree is less under high confining pressure than under low confining pressure;② Under a confining pressure of 40kPa, within 1% strain ranges, the needed dynamic stress to reach the specified strain is just 0.01kN, and the peak stress decreases with the augmentation of dynamic strain, when peak stress increases to 0.204kN, the sample is destructed; Under a confining pressure of 90kPa, soil radial particles are closely spaced, within 2% strain ranges also only a dynamic stress of 0.01kN is needed to reach the specified strain, and with the increase of dynamic strain, the samples are destructed when dynamic strain increases to 0.267kN. The dynamic failure stress of Lishi loess increases gradually with the increase of confining pressure, and the linear regression equation is бd=0.0011б3+0.1590, the correlation coefficient is 0.9944. ③According to Mohr-Coulomb failure criterion, the strength parameters of Lishi loess in somewhere of the north of shaanxi are C=30.33kPa，φ=14°. Under the dynamic shearing action, the dynamic effective strength parameters are obviously less than static effective strength parameters, this indicates that the soil consolidation effect reduced and the particles displaced and occluded each other.

Oxidative Stress Relaxation of Natural Rubber Vulcanized with Di-Tertiary-Butyl Peroxide

1956 ◽  
Vol 29 (3) ◽  
pp. 1043-1046 ◽  
Author(s):  
Svein Ore
Keyword(s):  
Oxidative Stress ◽  
Stress Relaxation ◽  
Carbon Black ◽  
Natural Rubber ◽  
First Grade ◽  
Main Reaction ◽  
Reaction Products ◽  
Hydrogen Atoms ◽  
Tertiary Butyl ◽  
Butyl Peroxide

Abstract It has been shown by Farmer and Moore that natural rubber can be vulcanized with di-tert.-butyl peroxide (DTBP), Presumably the free radicals formed by the unimolecular decomposition of the peroxide abstract some of the more labile (e.g., α-methylenic) hydrogen atoms, leading to direct C—C crosslinks between the rubber molecules, with tert.-butanol and acetone as the main reaction products. This preliminary communication presents some of the results of an investigation of the oxidative stress relaxation of the following types of DTBP vulcanizates. (A) First grade pale crepe, DTBP, and carbon black (MPC) mixed on the mill and vulcanized in a press. The carbon black was added to minimize the deleterious effect of impurities. (B) Purified rubber vulcanized: (1) in aqueous heating media; (2) in the press; (3) in DTBP vapor.

Relaxation of Stress and Electrical Resistivity in Carbon-Filled Vulcanizates at Moderate and High Extensions

1971 ◽  
Vol 44 (1) ◽  
pp. 185-198 ◽  
Author(s):  
A. K. Sircar ◽  
A. Voet ◽  
F. R. Cook
Keyword(s):  
Particle Size ◽  
Electrical Resistivity ◽  
Stress Relaxation ◽  
Carbon Black ◽  
Carbon Chain ◽  
Relaxation Mechanism ◽  
Initial Increase ◽  
Relaxation Rates ◽  
Carbon Structures ◽  
Chain Alignment

Abstract Measurements have been made of the relaxation of stress and electrical resistivity of stretched carbon black-loaded vulcanizates throughout the elongation range up to break. Data were obtained for vulcanizates with a number of carbon blacks, varying in particle size and in structure. The influence of the degree of loading as well as of the type of elastomer was investigated. In a gum vulcanizate there is initially a decline in rate of stress relaxation at increasing elongation as a result of the limited extensibility of the elastomer chains, followed by a constant rate at higher extensions. The level for a carbon-loaded vulcanizate is always higher than for the gum. At lower elongations this is due to an additional relaxation mechanism, the reformation of broken weak bonds between elastomer and filler particles upon standing. At medium and higher elongations, the stress relaxation rate for the carbon-filled vuleanizates increases sharply with increasing extension, due to persistent carbon chain alignment and, at still higher elongation, to rupture of carbon-elastomer bonds, both phenomena leading to additional modes of stress relaxation. Resistivity relaxation rates reflect changes in carbon black distribution. An initial increase at small extensions is due to rebuilding of destroyed transient structures. A decrease in relaxation rates for medium extension ranges is caused by persistent carbon chain alignment, less pronounced at increasing elongation. At the higher elongations carbon-elastomer bonds arc broken, leading to randomization of chains, resulting in negative relaxation rates with higher structure blacks at the highest elongations. All such effects depend to a large extent on the carbon structures. The influence of loading level, of particle size and of elastomer type is discussed.

Mechanism of stress relaxation in rubber filled with carbon black

1970 ◽  
Vol 12 (4) ◽  
pp. 1049-1060 ◽  
Author(s):  
G.M. Bartenev ◽  
N.M. Lyalina
Keyword(s):  
Stress Relaxation ◽  
Carbon Black

scholarly journals Dynamic stress relaxation of orthodontic thermoplastic materials in a simulated oral environment

2013 ◽  
Vol 32 (6) ◽  
pp. 946-951 ◽  
Author(s):  
Dongyu FANG ◽  
Ning ZHANG ◽  
Hui CHEN ◽  
Yuxing BAI
Keyword(s):  
Stress Relaxation ◽  
Dynamic Stress ◽  
Oral Environment

Stress relaxation of nitrile rubber composites filled with a hybrid metakaolin/carbon black filler under tensile and compressive forces

2018 ◽  
Vol 151 ◽  
pp. 181-188 ◽  
Author(s):  
Elisson Brum Dutra da Rocha ◽  
Felipe Nunes Linhares ◽  
Cléverson Fernandes Senra Gabriel ◽  
Ana Maria Furtado de Sousa ◽  
Cristina Russi Guimarães Furtado
Keyword(s):  
Stress Relaxation ◽  
Carbon Black ◽  
Nitrile Rubber ◽  
Rubber Composites
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