Strain Energy as a Criterion for Stress Softening in Carbon-Black-Filled Vulcanizates

1966 ◽  
Vol 39 (3) ◽  
pp. 597-608 ◽  
Author(s):  
E. M. Dannenberg ◽  
J. J. Brennan
Keyword(s):  
Carbon Black ◽  
Energy Loss ◽  
Natural Rubber ◽  
Strain Energy ◽  
Energy Input ◽  
Strain Curve ◽  
Quantitative Measure ◽  
Initial Strain ◽  
Stress Softening ◽  
Strain Energy Loss

Abstract Stress softening of vulcanizates of SBR 1500 containing different blacks possessing the same “structure” but varying in surface activity, and effects of different black loadings, of black structure levels, and of particle size, were investigated. It was concluded: 1. Strain-energy loss can be used as a quantitative measure of stress softening, and initial strain-energy input as a measure of prestress severity. 2. The effects of carbon black and polymer variables can be normalized in a single general relationship by plotting per cent strain-energy loss as a function of initial strain-energy input for filled vulcanizates. 3. With the exception of natural rubber, gum vulcanizates studied showed no stress softening. The stress softening of natural rubber gum vulcanizates is attributed mainly to stress-crystallization. 4. Stress-softening of filled vulcanizates is not a completely reversible process. Rates of stress recovery are reasonably rapid. 5. The degree of stress softening can be predicted from the initial stress—strain curve, the prestress severity desired, and the general correlation based on strain-energy considerations found in this study. 6. Prestressing reduces abrasion resistance as measured in the laboratory.

Study on Evaluation Method of Corroded Reinforcing Steel

2010 ◽  
Vol 26-28 ◽  
pp. 1184-1189 ◽  
Author(s):  
Ying Zi Zhang ◽  
Ying Fang Fan ◽  
Hong Nan Li ◽  
Xue Nan Wu
Keyword(s):  
Weight Loss ◽  
Energy Loss ◽  
Cross Section ◽  
Strain Energy ◽  
Evaluation Method ◽  
Reinforcing Bars ◽  
Reinforcing Bar ◽  
Important Index ◽  
Steel Bars ◽  
Strain Energy Loss

Corrosion ratio is an important index to study the mechanical deteriorates of the steel bars, which has a significant effect to evaluate the residual bearing capacity of reinforced concrete structures. To investigate the mechanical properties of the corroded steel bars, Strain energy loss as corrosion ratio is firstly proposed. Tensile test are conducted on ribbed and plain steels, which are corroded by acceleration corrosion method. Comparing with the weight loss and cross-section loss to describe the effect of corrosion of reinforcing bar, the strain energy loss of reinforcing bars is calculated by Simpson quadrature. Results from this paper and other researchers’ test suggest that the strain energy loss may be a better parameter than weight loss or section loss which to assess the corroded steel bars.

Stress Softening in Natural Rubber Vulcanizates. IV. Unfilled Vulcanizates

1967 ◽  
Vol 40 (3) ◽  
pp. 840-848 ◽  
Author(s):  
J. A. C. Harwood ◽  
A. R. Payne
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Molecular Networks ◽  
Mullins Effect ◽  
Total Recovery ◽  
Stress Softening ◽  
Affine Deformation ◽  
Nonaffine Deformation ◽  
Natural Rubber Vulcanizates ◽  
Random State

Abstract Stress softening (Mullins effect) in gum natural rubber vulcanizates is similar in magnitude to that in carbon black filled vulcanizates. The amount of stress softening is slightly greater in vulcanizates cured to produce predominantly polysulfide crosslinks than in those containing monosulfide or carbon to carbon crosslinks. The total recovery of stress softening in the vulcanizates containing monosulfide or carbon to carbon crosslinks suggests that the phenomenon is attributable to a quasiirreversible rearrangement of molecular networks due to localized non-affine deformation resulting from short chains reaching the limit of their extensibility. This nonaffine deformation results in a displacement of the network junctions from their initial random state.

Influence of Large Static Deformation on the Dynamic Properties of Polymers Part II. Influence of Carbon Black Loading

1981 ◽  
Vol 54 (4) ◽  
pp. 857-870 ◽  
Author(s):  
E. A. Meinecke ◽  
S. Maksin
Keyword(s):  
Carbon Black ◽  
Energy Loss ◽  
Amplification Factor ◽  
Complex Modulus ◽  
Dynamic Properties ◽  
Strain Curve ◽  
Static Stress ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Static Modulus

Abstract The influence of carbon black loading on the dynamic properties of statically deformed elastomers has been investigated. The energy loss per cycle was found to increase according to the square of the strain amplification factor as expressed by the Guth-Gold-Einstein equation. The dynamic complex modulus |E*| is approximately equal to the static modulus obtained from the slope of the static stress-strain curve. The influence of carbon black loading on E* can, therefore, be predicted from its influence on the static stress-strain curve which was found to be governed by the first power of the strain amplification factor. The tangent of the loss angle can thus be predicted from |E*| and the energy loss per cycle. It does not only depend upon the dynamic viscosity of the material; it also depends upon the shape of the stress-strain curve as well.

Dynamic-Mechanical Characteristics of Rubber Compounds

1956 ◽  
Vol 29 (4) ◽  
pp. 1215-1232 ◽  
Author(s):  
S. de Mey ◽  
G. J. van Amerongen
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Loss Factor ◽  
Mechanical Characteristics ◽  
Strain Curve ◽  
Shear Loading ◽  
Butyl Rubber ◽  
Amplitude Dependence ◽  
Dynamic Mechanical ◽  
Rubber Compounds

Abstract Since rubber articles are often exposed in service to small periodic deformations, great interest attaches to the dynamic-mechanical characteristics of rubber. It has been established that the conditions under which these characteristics are determined have a pronounced influence on the results obtained, so that the measurements must be undertaken under precisely specified conditions. A new test apparatus is described for measuring the dynamic-mechanical characteristics, with which measurements can be performed at any desired stress setting, frequency, temperature, and amplitude on the same samples, both for compression and for shear loading. The incompressibility of filler-free natural-rubber compounds has been demonstrated by measurements made on samples with different shape factors and with varied static initial stress, under compression and with shear loading. The temperature, frequency, and amplitude dependence of the dynamic-mechanical characteristics of different rubber compounds is discussed on the basis of a number of measurements. The maximum value of the loss factor, which occurs in the vicinity of the second-order transition point, appears at a higher temperature in GR-S (cold rubber), Vulkollan, and Butyl rubber than in natural rubber. There is a connection between this fact and the much greater frequency and temperature dependence of Butyl rubber compared to natural rubber in the vicinity of room temperature. A compound based on natural rubber and a styrene-butadiene (85/15) co-polymer shows two maxima in the loss factor. One of these is characteristic of natural rubber, the other of the polymer. The dynamic characteristics of filler-free rubber compounds are not very sensitive to amplitude. It is found that the marked amplitude dependence of reinforced rubber compounds cannot be accounted for by increased temperature or by any nonlinearity of the stress-strain curve. The influence of composition on the dynamic-mechanical characteristics of natural rubber has been tested for a number of compounds. It is established that the carbon black types can have a significant effect on the E′ modulus. At small amplitudes the magnitude is greater for a compound containing SAF or EPC carbon black than for one containing HAF carbon black. Natural rubber reinforced with Aerosil or aniline resin shows a small loss factor, while compounds vulcanized with Thiuram show a large one. The present study is part of a fundamental investigation on rubber carried out by the Research Division of the Rubber-Stichting in Delft under the direction of H. C. J. de Decker.

Extraction and identification of fillers and pigments from pyrolyzed rubber and tire samples

1996 ◽  
Vol 54 ◽  
pp. 174-175
Author(s):  
P. Sadhukhan ◽  
J. B. Zimmerman
Keyword(s):  
Zinc Oxide ◽  
Electron Microscope ◽  
Carbon Black ◽  
Natural Rubber ◽  
Transmission Electron Microscope ◽  
Rolling Resistance ◽  
Synthetic Polymers ◽  
Nitrogen Atmosphere ◽  
Transmission Electron ◽  
Curing Agents

Rubber stocks, specially tires, are composed of natural rubber and synthetic polymers and also of several compounding ingredients, such as carbon black, silica, zinc oxide etc. These are generally mixed and vulcanized with additional curing agents, mainly organic in nature, to achieve certain “designing properties” including wear, traction, rolling resistance and handling of tires. Considerable importance is, therefore, attached both by the manufacturers and their competitors to be able to extract, identify and characterize various types of fillers and pigments. Several analytical procedures have been in use to extract, preferentially, these fillers and pigments and subsequently identify and characterize them under a transmission electron microscope.Rubber stocks and tire sections are subjected to heat under nitrogen atmosphere to 550°C for one hour and then cooled under nitrogen to remove polymers, leaving behind carbon black, silica and zinc oxide and 650°C to eliminate carbon blacks, leaving only silica and zinc oxide.

Rubber Fracture Characterization Using J-Integral

1988 ◽  
Vol 16 (1) ◽  
pp. 44-60 ◽  
Author(s):  
C. L. Chow ◽  
J. Wang ◽  
P. N. Tse
Keyword(s):  
Crack Initiation ◽  
Carbon Black ◽  
Natural Rubber ◽  
Fracture Parameter ◽  
J Integral ◽  
Specimen Length ◽  
Fracture Characterization ◽  
Premature Failure ◽  
Testing Procedures ◽  
Material Evaluation

Abstract The use of the J-integral to investigate fracture characterization in a carbon black reinforced natural rubber is described. Three applications to crack initiation are included: two based on the use of a hypothetical zero specimen length and one on conventional testing procedures for metals. While the validity of the zero-length methods is questionable, the conventional method yielded a consistent Jc value of 1.01 N/mm for a typical tire compound. This value was obtained from 24 combinations of varying specimen geometries and pre-crack lengths. The J-integral is revealed as a valid fracture parameter that is applicable not only for material evaluation but also for designing tire structures to resist premature failure. These conclusions disagree with those from an earlier investigation, so the causes for the discrepancies are examined and discussed.

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