Stress softening in natural rubber vulcanizates. Part III. Carbon black-filled vulcanizates

1966 ◽  
Vol 10 (2) ◽  
pp. 315-324 ◽  
Author(s):  
J. A. C. Harwood ◽  
A. R. Payne
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Stress Softening ◽  
Natural Rubber Vulcanizates

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.

Structural Characterization of Filled Vulcanizates Part 1. Determination of the Concentration of Chemical Crosslinks in Natural Rubber Vulcanizates Containing High Abrasion Furnace Black

1967 ◽  
Vol 40 (3) ◽  
pp. 866-882 ◽  
Author(s):  
M. Porter
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Volume Fraction ◽  
Exponential Relationship ◽  
Furnace Black ◽  
Simple Linear Relationship ◽  
Chemical Crosslinks ◽  
Natural Rubber Vulcanizates

Abstract The degree to which HAF black restricts the swelling of natural rubber vulcanizates in n-decane has been determined using a vulcanizing system in which the stoichiometry of crosslinking is unaffected by the carbon black. The dependence of the degree of restriction, as measured by the ratio of the volume fractions of rubber in the filled and unfilled vulcanizates swollen to equilibrium, on the concentration of carbon black follows an exponential relationship previously proposed by Lorenz and Parks. This is found to be equivalent to a simple linear relationship between the apparent and actual crosslink concentrations: napparent/nactual=1+Kϕ, where K is a constant characteristic of the filler and φ is its volume fraction in the vulcanizate. The relation has been used to determine actual crosslink concentrations in filled natural rubber vulcanizates. HAF black is found to cause increases of up to 25 per cent in the yield of polymer to polymer crosslinks in conventional sulfur vulcanizing systems, accompanied by changes in rate of cure and of crosslink reversion. All these are small compared with the effect of the filler on many physical properties.

Effect of Crosslink Density on Cut Growth in Black-Filled Natural Rubber Vulcanizates

2002 ◽  
Vol 75 (5) ◽  
pp. 935-942 ◽  
Author(s):  
G. R. Hamed ◽  
N. Rattanasom
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Crack Growth ◽  
Crosslink Density ◽  
Longitudinal Crack ◽  
Test Pieces ◽  
Filled Rubber ◽  
Longitudinal Cracks ◽  
Natural Rubber Vulcanizates ◽  
High Crosslink Density

Abstract Tensile strengths, σb, of gum and N115-filled natural rubber test pieces, with and without edge pre-cuts, have been determined. At low crosslink density, the regular (uncut) σb of filled and gum vulcanizates is similar. However, at high crosslink density, the gum NR becomes brittle, while the corresponding filled rubber remains strong and resistant to cut growth. It is proposed that the tightly linked gum does not strain-crystallize appreciably during stretching, but that its filled counterpart does. Carbon black appears capable of inducing crystallization in a network that alone remains amorphous during extension. Filled vulcanizates of various crosslink densities have similar normal tensile strengths ( ≈ 30 MPa), but strengths differ, sometimes more than twofold, if a pre-cut is present. Lightly crosslinked specimens containing a small cut have strengths that depend very weakly on cut size, c. Furthermore, these develop long longitudinal cracks from which catastrophic rupture initiates. With larger cuts, strength decreases more rapidly with increasing c, there is less longitudinal crack growth, and rupture initiates near the original cut tip. In contrast, the strength of a highly crosslinked vulcanizate is sensitive to small cuts and test pieces exhibit minimal longitudinal cracking before failure.

Modeling of Carbon Black Filled Natural Rubber Vulcanizates by the Standard Triboelastic Solid

1999 ◽  
Vol 72 (4) ◽  
pp. 673-683 ◽  
Author(s):  
V. A. Coveney ◽  
D. E. Johnson
Keyword(s):  
Mathematical Modeling ◽  
Carbon Black ◽  
Natural Rubber ◽  
Dynamic Behavior ◽  
Low Frequency ◽  
Specific Reference ◽  
Published Data ◽  
General Terms ◽  
Wide Range ◽  
Natural Rubber Vulcanizates

Abstract Mathematical modeling of the dynamic behavior of vulcanizates is reviewed with the emphasis on carbon black filled natural rubber (NR). The 3 constant standard triboelastic solid (STS) model and its behavior are described, in general terms and with specific reference to low frequency shear data for a wide range of filled NR vulcanizates. Good general agreement is found between model and experiment for the data obtained at strain amplitudes down to 0.01; there is also acceptably good correlation between carbon black loading and values of STS constants. For previously published data down to very low strain amplitudes (1×10−4), agreement is much less satisfactory.

Internal Field Emission in Carbon Black-Loaded Natural Rubber Vulcanizates

1964 ◽  
Vol 37 (2) ◽  
pp. 348-354 ◽  
Author(s):  
L. K. H. van Beek ◽  
B. I. C. F. van Pul
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Field Emission ◽  
Electron Micrographs ◽  
Internal Field ◽  
Emission Characteristics ◽  
Furnace Black ◽  
Three Samples ◽  
Insulating Gap ◽  
Natural Rubber Vulcanizates

Abstract The nonohmic behavior of carbon black-loaded natural rubber vulcanizates was studied. Three samples contained high-abrasion furnace black (HAF) in good, moderate, and poor dispersion. Another sample contained a good dispersion of medium thermal black (MT). The nonohmic behavior of the poor HAF dispersion and that of the MT dispersion could be interpreted as due to internal field emission across insulating gap widths of 2 and 2.5 µ. The existence of such gaps was confirmed by electron micrographs. No clear evidence of internal field emission could be obtained for the good and moderate HAF dispersions where, according to electron micrographs, the gaps are much narrower. There is some indication that the degree of dispersion can be correlated with field emission characteristics.

scholarly journals Carbon Black Network Structure in Natural Rubber Vulcanizates

Seikei-Kakou ◽  
2016 ◽  
Vol 28 (6) ◽  
pp. 210-213
Author(s):  
Atsushi Kato ◽  
Yuko Ikeda ◽  
Shinzo Kohjiya
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Network Structure ◽  
Natural Rubber Vulcanizates

Solid-State C-13 NMR Studies of Vulcanized Elastomers XVII. Effect of Carbon Black Grade on the Network Structure in Natural Rubber Vulcanizates

1997 ◽  
Vol 70 (4) ◽  
pp. 671-680 ◽  
Author(s):  
Makio Mori ◽  
Jack L. Koenig
Keyword(s):  
Solid State ◽  
Carbon Black ◽  
Natural Rubber ◽  
Network Formation ◽  
Physical Adsorption ◽  
Nmr Studies ◽  
Carbon Black Concentration ◽  
Effective Level ◽  
The Individual ◽  
Natural Rubber Vulcanizates

Abstract The vulcanization chemistry and network formation of carbon black filled natural rubber vulcanized with sulfur and TBBS were studied using solid-state C-13 NMR and equilibrium swelling measurements. A reduction in the sulfur rank of the A1 type sulfide and increased production of B1 type polysulfide are observed when the carbon black concentration increases in natural rubber. At the same loading level, the structural property or grade of carbon black does not affect qualitatively the type of sulfide formation. The efficiency of the intermolecular crosslinking over the whole range of sulfurizations is 45.7% for the unfilled vulcanizate. The extent of the chemical sulfurization reactions (NMR result) is constant with black incorporation, while the total network (swelling result) increases with increases in the black loading. The amount of physical entanglements, estimated from the comparison of the NMR and swelling results, is found to increase linearly with the carbon black concentration. The entanglements increase as a function of the 300% modulus, which suggests that the effective level of reinforcement depends on the nature of the individual carbon black. It is assumed that physical adsorption plays a major role in the polymer-filler interactions in the natural rubber/carbon black system.

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