Strain Amplification of Elastomers Filled with Carbon Black in Tensile Deformation

1988 ◽  
Vol 61 (1) ◽  
pp. 137-148 ◽  
Author(s):  
N. Nakajima ◽  
J. J. Scobbo
Keyword(s):  
Carbon Black ◽  
Tensile Stress ◽  
Tensile Deformation ◽  
Molecular Architecture ◽  
Dynamic Shear ◽  
Treatment Procedure ◽  
Stress Strain ◽  
Strain Measurements ◽  
Unique Pattern ◽  
Data Treatment

Abstract This work is based on data previously obtained by the tensile stress-strain and dynamic-shear measurements with several gum rubbers and carbon-black-filled compounds. The gum rubbers were three NBR's of different molecular architecture and two SBR's, one of which was oil extended. The compounds contained 40 phr of N550 carbon black. Through the data treatment procedure developed in this work, the strain amplifications in the dynamic shear and tensile stress-strain measurements were evaluated with the uncrosslinked compounds. Each compound showed a unique pattern of strain amplification.

Comparison of Tensile and Shear Behavior of Carbon-Black-Filled Elastomers

1987 ◽  
Vol 60 (4) ◽  
pp. 761-780 ◽  
Author(s):  
N. Nakajima ◽  
J. J. Scobbo ◽  
E. R. Harrell
Keyword(s):  
Carbon Black ◽  
Tensile Stress ◽  
High Speed ◽  
Complex Viscosity ◽  
Small Strain ◽  
Shear Behavior ◽  
Dynamic Shear ◽  
Stress Strain ◽  
Strain Behavior ◽  
Tensile Tester

Abstract Four NBR's and 2 SBR's with 40 phr carbon black and one SBR with 56 phr carbon black were characterized in both tensile stress-strain behavior and small-strain dynamic-shear behavior. The room temperature tensile stress-strain behavior was determined at strain rates of 0.00690, 0.0187, 0.0975, 0.0162, and 0.253 s−1. For dynamic-shear observations, loss and storage moduli were used to calculate the complex viscosity-frequency curve at small deformations and frequencies of 0.1 to 100 rad/s. Also, these data from tensile and shear experiments were compared with previous data from a capillary rheometer, high-speed tensile tester, and oscillatory tensile tester. Strain-time correspondence was found applicable to large-deformation tensile data up to the yield point. The formation of an anisotropic aggregate density in elongational deformation explains the higher viscosity and modulus for tensile behavior relative to small-strain shear behavior at similar conditions. In shear deformation and flow, the formation of an anisotropic density of aggregates does not seem to occur appreciably.

Capillary Rheometry of Carbon-Black-Filled Butadiene—Acrylonitrile Copolymers

1975 ◽  
Vol 48 (4) ◽  
pp. 615-622 ◽  
Author(s):  
N. Nakajima ◽  
E. A. Collins
Keyword(s):  
Shear Rate ◽  
Carbon Black ◽  
Tensile Stress ◽  
Capillary Flow ◽  
Complex Viscosity ◽  
Appreciable Effect ◽  
Stress Strain ◽  
Capillary Rheometry ◽  
Strain Behavior ◽  
Acrylonitrile Copolymers

Abstract Capillary rheometry of carbon-black-filled butadiene—acrylonitrile copolymers at 125°C was performed over a wide shear rate range. The data were corrected for pressure loss in the barrel and at the capillary entrance, and for the non-Newtonian velocity profile (Rabinowitsch correction). No appreciable effect of pressure on viscosity was observed. The die swell values were very small, 1.1–1.4. This fact and the shape of the plots of shear stress vs. shear rate imply the presence of a particulate structure, which is probably built by carbon black surrounded with bound rubber. Unlike the behavior of raw amorphous elastomers, the steady-shear viscosity, the dynamic complex viscosity, and the viscosity calculated from tensile stress-strain behavior were significantly different from each other. That is, the capillary flow data indicated an alteration of the structure towards strain softening, and the tensile stress-strain behavior showed strain hardening, indicating retention of the structure up to the yield point. In the dynamic measurement, being conducted at very small strain, the structure is least disturbed. With unfilled elastomers essentially the same deformational mechanism was believed to be responsible in these three measurements, because the results can be expressed by a single master curve.

Tensile Stress—Strain Measurements for Characterization of Gum Elastomers and Filled Compounds

1990 ◽  
Vol 63 (4) ◽  
pp. 624-636 ◽  
Author(s):  
N. Nakajima ◽  
M. H. Chu ◽  
R. Babrowicz
Keyword(s):  
Shear Modulus ◽  
Tensile Stress ◽  
Shear Deformation ◽  
Tensile Modulus ◽  
Nonlinear Behavior ◽  
Material Behavior ◽  
Structural Constraints ◽  
Stress Strain ◽  
Strain Measurements ◽  
Diene Rubbers

Abstract For a gum elastomer in its amorphous, isotropic state, shear modulus and tensile modulus are related with a factor of three. This relation is maintained in the range of temperature and time scale defining the rubbery region of the material behavior. When a large deformation is imposed, for example, in tensile stress—strain measurements, the above relation may still be preserved, if the nonlinear behavior can be linearized. The strain—time correspondence principle is the linearization scheme of this work. When a gum elastomer contains various structural constraints, the factor three relation does not apply, even after the application of the above linearization scheme. Example of constraints are excessive amounts of long branches, gel, molecular associations, and reinforcing fillers. These constraints usually make the factor larger than three. This is because the constraints make the large, elongational deformation more difficult to achieve compared to shear deformation. An example of gum elastomer in this work is a polyethylacrylate containing a significant amount of gel. With this polymer, both the presence of gel and the molecular association act as the constraints. However, when 50 phr of carbon blacks are added, the fillers do not act as strong constraints as they do when they are in the diene rubbers. This is because the polyethylacrylate is known to have a weaker affinity to carbon black compared to the diene rubbers. Triblock copolymers, styrene—isoprene—styrene, were examined according to the above treatment; 25% polystyrene copolymer exhibited crosslink-like behavior by the polystyrene domains. However, 14% polystyrene copolymers acted as if they are no crosslinks. When these copolymers are diluted to 44% with an addition of 56% tackifier, the ratio of tensile to shear modulus became less than three. The styrene domains must have effective crosslinks at the small shear deformation, but at large tensile deformations such crosslinks must not be present.

Mechanism of the Modulus Increase of Carbon-Black-Filled Rubber at Small Extension

2011 ◽  
Vol 284-286 ◽  
pp. 1969-1973
Author(s):  
Xiao Ling Hu ◽  
Yong Ouyang ◽  
Xiong Zhou ◽  
Wen Bo Luo
Keyword(s):  
Carbon Black ◽  
Tensile Stress ◽  
Volume Fraction ◽  
Tensile Modulus ◽  
Homogenization Method ◽  
Stress Strain ◽  
Filled Rubber ◽  
Strain Relationship ◽  
Filled Rubbers ◽  
Relationship Of

The tensile stress-strain relationship of rubbers is fairly linear and can be used for obtaining tensile modulusE. In this work we analyzed the tensile stress-strain relationship of filled rubber experimentally and employed the extended 2D homogenization method to compute the modulus of the carbon black (CB) filled rubbers with various CB volume fractions ranging from 5% to 25%. The results reveal that the modulus of CB-filled rubbers increased with the increase in CB volume fraction and in CB aggregation.

Dynamic Viscoelastic Properties of Raw Butadiene—Acrylonitrile Elastomers

1974 ◽  
Vol 47 (4) ◽  
pp. 778-787 ◽  
Author(s):  
N. Nakajima ◽  
E. A. Collins ◽  
P. R. Kumler
Keyword(s):  
Shear Stress ◽  
Tensile Stress ◽  
Viscoelastic Properties ◽  
High Speed ◽  
Master Curve ◽  
Viscoelastic Behavior ◽  
Master Curves ◽  
Stress Strain ◽  
Strain Measurements ◽  
Using Data

Abstract The dynamic viscoelastic properties of four samples of butadiene—acrylonitrile raw elastomers, were obtained with a Rheovibron at 110 Hz and temperature range of −80 to 160°C. The complex properties were in agreement with the master curves obtained previously from stress-strain measurements. A master curve encompassing 13 decades of time was constructed using data from Mooney rheometer shear stress-strain, MTS high speed tensile stress-strain, and the Rheovibron. The master curve represents the rubbery region of viscoelastic behavior in terms of time, temperature, and the magnitude of deformation up to the breaking point. This study demonstrates that corresponding states can be found between small (ca. 1 per cent) and large deformation up to break (e.g., 1400 per cent).

Nature of Network, Carbon-Black-Rubber Interaction and Heat Aging of Polyethylacrylate Vulcanizates

1989 ◽  
Vol 62 (2) ◽  
pp. 357-366 ◽  
Author(s):  
N. Nakajima ◽  
R. A. Miller
Keyword(s):  
Carbon Black ◽  
Chemical Nature ◽  
Tensile Modulus ◽  
Large Strains ◽  
Molecular Architecture ◽  
Strain Measurements ◽  
Small Strains ◽  
Two Samples ◽  
Weight One ◽  
The Difference

Abstract Two commercial polyethylacrylate elastomers, having about 50 Mooney Index were selected. They were compounded with 50 parts of N330 carbon black per 100 parts of rubber by weight. One sample having epoxide (EP) crosslinking sites was crosslinked with ammoniumbenzoate. The other having double-bonds by copolymerizing with ethylidene norbornene (ENB) was crosslinked with a sulfur system. The vulcanizates were oven aged at 175°C for 70 h. Tensile stress-strain measurements were performed with the gum rubbers, uncured compounds, unaged vulcanizates, and heat-aged vulcanizates. The data presented as tensile modulus—strain curves revealed the following: at all strain levels, the moduli of ENB gum samples were lower than those of EP gums. After compounding with carbon black, the moduli of two samples became very similar. This indicates that ENB has more affinity with carbon black than EP has. The vulcanizates of two samples has matching moduli at 10% strain but a difference in network structure, since the molecular architecture of the gum rubbers were very different. After heat aging, moduli at small strains increased significantly but not at large strains. The increases were very similar for both samples. The heat-aging characteristics may be very similar for both samples, in spite of the difference in the chemical nature of the crosslinks.

Viscoelastic Characterization of Long Branching and Gel in Elastomers by Comparison of Large and Small Deformational Behavior

1987 ◽  
Vol 60 (4) ◽  
pp. 742-760 ◽  
Author(s):  
N. Nakajima ◽  
J. J. Scobbo ◽  
E. R. Harrell
Keyword(s):  
Tensile Stress ◽  
Shear Behavior ◽  
Dynamic Shear ◽  
Stress Strain ◽  
Strain Behavior ◽  
Strain Data ◽  
Deformational Behavior ◽  
Varied Chemical ◽  
Reduced Data

Abstract Ten different raw elastomers of varied chemical structure and Mooney viscosity were characterized with both tensile stress-strain behavior and dynamic shear behavior. The room temperature tensile stress-strain behavior was determined at strain rates of 0.239, 0.0892, and 0.00653 sec−1. These stress-strain data were reduced with a use of strain-time correspondence principle. The dynamic-shear behavior was observed over the frequency range from 10−2 to 102 rad/s. Double logarithmic Cole-Cole plots were used to characterize a relative degree of long branching and gel content. The reduced data of tensile stress-strain measurements were compared to the data of dynamic measurements. From this comparison, the sample containing a long-range crosslinked network was differentiated from that containing microgel.

Nonlinear Viscoelastic Behavior of Butadiene—Acrylonitrile Copolymers Filled with Carbon Black

1978 ◽  
Vol 51 (2) ◽  
pp. 322-334 ◽  
Author(s):  
N. Nakajima ◽  
H. H. Bowerman ◽  
E. A. Collins
Keyword(s):  
Carbon Black ◽  
Tensile Stress ◽  
Strain Hardening ◽  
Strain Softening ◽  
Capillary Flow ◽  
Complex Viscosity ◽  
Angular Frequency ◽  
Stress Strain ◽  
Flow Measurements ◽  
Acrylonitrile Copolymers

Abstract Various viscoelastic measurements including dynamic mechanical measurements in tension at 110 Hz from −60–160°C, tensile stress relaxation measurements with 100% elongation at 25, 54, and 98°C, capillary flow measurements at 70, 100, and 125°C, and high-speed tensile stress-strain measurements carried to break at 25, 56, and 98°C were performed on four samples of carbon-black-filled butadiene—acrylonitrile copolymers. All the data were treated with the same equation for time-temperature conversion. The capillary viscosity—shear rate curves were significantly lower than the complex viscosity—angular frequency curves, indicating “strain softening” with extrusion. The viscosity was estimated from the stress-strain relationship at the yield point. The viscosity as a function of the strain rate is significantly higher than the complex viscosity as a function of angular frequency, indicating “strain hardening” with extension. The strain softening and strain hardening are attributable to the structural changes upon deformation of the carbon-black-filled elastomers. With the unfilled elastomers, neither strain softening nor strain hardening were observed in similar measurements.

Anisotropy Induced in an Uncrosslinked Elastomer Via Large Strain Deformation

1985 ◽  
Vol 58 (2) ◽  
pp. 407-420 ◽  
Author(s):  
G. R. Hamed ◽  
J. H. Song
Keyword(s):  
Tensile Stress ◽  
Total Energy ◽  
Large Scale ◽  
Large Strain ◽  
Relaxation Times ◽  
Stress Strain ◽  
Strain Measurements ◽  
Resistance To Deformation ◽  
Initial Resistance ◽  
The Moment

Abstract The anisotropy induced in an ungelled SBR elastomer upon large scale deformation and the rate at which the deformed elastomer returns to its original state upon removal of the deforming force were investigated. In these experiments, a standard birefringence technique was unsuitable for measuring the extent of orientation after release, however, tensile stress-strain measurements successfully showed the presence of anisotropy. After prestraining and then releasing, samples have an initial resistance to deformation which is the same both parallel and perpendicular to the prestraining direction. However, testpieces cut parallel with the prestraining direction show stress-strain curves that lie above those for cross-cut specimens at high elongations, while cross-cut samples have stress-strain curves remarkably similar to those of the isotropic controls. With increasing time after prestraining or for larger prestrains, the normalized anisotropy, at intermediate elongations, becomes negative; that is, in this region, it becomes easier to deform “parallel” specimens than to deform “perpendicular” specimens. This phenomenon is proposed to be the result of two opposing entanglement networks—an original one, which remains in tension, and a compressed one, which was formed by chains re-entangling while the sample was extended. Although the shapes of the “parallel” and “perpendicular” stress-strain curves may be quite different, the total energy required to rupture the samples in both cases is similar. Finally, for a lightly crosslinked sample, it is demonstrated that after various prestrains, hold times, and relaxation times before testing after prestraining, the normalized anisotropy is a unique function of the residual extension at the moment when the specimens were tested.

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