Effect of Carbon Black Concentration on Cut Growth in NR Vulcanizates

Abstract Dumbbell specimens containing edge razor-cuts of various depths, c, have been prepared from sulfur-vulcanized natural rubber compositions containing 0–75 phr of N115 black. Normal tensile strengths (c=0) of the gum and all black-filled samples are similar. However, cut growth resistance (CGR) relative to the gum, depends strongly on black content and cut depth. With about 6–15 phr of black, filled specimens are weaker than the gum and fracture occurs by simple forward growth of the original cut tip, i.e., a single crack develops and propagates laterally. At about 18 phr of black, filled specimens become stronger than the gum and cracking becomes complex. Prior to catastrophic rupture, crack splitting occurs near the original cut tip - forming at least two slowly-growing, longitudinal cracks. These reduce the stress concentration caused by the cut, thereby delaying rupture, and marking the onset of “reinforcement”. All pre-cut specimens containing 18–75 phr of black are stronger than the gum and they exhibit crack splitting. Specimens containing 50 phr of black have the highest strength - being about ten times as strong as the gum when cuts are large. The decrease in CGR at low levels of black and increase at high levels is attributed to competing effects upon the addition of carbon black to NR.

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

Rubber Chemistry and Technology ◽

10.5254/1.3547693 ◽

2002 ◽

Vol 75 (5) ◽

pp. 935-942 ◽

Cited By ~ 20

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.

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

Rubber Chemistry and Technology ◽

10.5254/1.3538453 ◽

1997 ◽

Vol 70 (4) ◽

pp. 671-680 ◽

Cited By ~ 15

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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Cut Growth in Vulcanizates of Natural Rubber, cis-Polybutadiene, and a 50/50 Blend during Single and Repeated Extension

Rubber Chemistry and Technology ◽

10.5254/1.3538404 ◽

1996 ◽

Vol 69 (5) ◽

pp. 807-818 ◽

Cited By ~ 39

Author(s):

G. R. Hamed ◽

H. J. Kim ◽

A. N. Gent

Keyword(s):

Tensile Strength ◽

Natural Rubber ◽

Crack Tip ◽

Forward Direction ◽

Secondary Crack ◽

Abrupt Decrease ◽

Considerable Distance ◽

Secondary Cracks ◽

Cut Depth ◽

Longitudinal Cracks

Abstract A typical passenger sidewall composition was employed using three elastomer systems NR, BR, and a 50/50 blend of NR and BR. Tensile strips with edge cuts of various depths were strained in two ways continuously increasing extension up to rupture, or repeatedly stretching them to progressively higher strains until failure occurred. For BR, the tensile strength σb decreased steadily with increasing cut depth, c, while NR and NR/BR showed an abrupt decrease in σb at a critical cut size, ccr. This is attributed to crystallization of NR throughout the specimen at high strains, when c<ccr, while crystallization is confined to the crack tip region when c>ccr. Furthermore, in samples of NR and NR/ BR the crack tip split, forming two secondary cracks which grew a considerable distance parallel to the direction of straining, and even turned backwards, before stopping. Rupture of the specimen did not occur until a new (third) crack was initiated from the smooth torn surface of the secondary crack. Under repeated straining NR specimens developed secondary cracks repeatedly in a characteristic alternating pattern. These are instances of severe “knotty” tearing. In contrast, in BR samples the initial cut always grew in a forward direction and secondary, longitudinal cracks did not develop.

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

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100163332 ◽

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.

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Preparation and characterization of natural rubber compounds with filler of oil palm empty bunches powder and carbon black

Functional materials ◽

10.15407/fm27.01.140 ◽

2020 ◽

Vol 27 (1) ◽

Keyword(s):

Carbon Black ◽

Natural Rubber ◽

Oil Palm ◽

Rubber Compounds

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Rubber Fracture Characterization Using J-Integral

Tire Science and Technology ◽

10.2346/1.2148797 ◽

1988 ◽

Vol 16 (1) ◽

pp. 44-60 ◽

Cited By ~ 14

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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Assessment of Graphene Oxide and Nanoclay Based Hybrid Filler in Chlorobutyl-Natural Rubber Blend for Advanced Gas Barrier Applications

Nanomaterials ◽

10.3390/nano11051098 ◽

2021 ◽

Vol 11 (5) ◽

pp. 1098

Author(s):

Jibin Keloth Paduvilan ◽

Prajitha Velayudhan ◽

Ashin Amanulla ◽

Hanna Joseph Maria ◽

Allisson Saiter-Fourcin ◽

...

Keyword(s):

Graphene Oxide ◽

Carbon Black ◽

Natural Rubber ◽

Gas Permeability ◽

Chemical Properties ◽

Barrier Properties ◽

Hybrid Filler ◽

Physical And Chemical ◽

Chlorobutyl Rubber ◽

And Chemical Properties

Nanomaterials have engaged response from the scientific world in recent decades due to their exceptional physical and chemical properties counter to their bulk. They have been widely used in a polymer matrix to improve mechanical, thermal, barrier, electronic and chemical properties. In rubber nanocomposites, nanofillers dispersion and the interfacial adhesion between polymer and fillers influences the composites factual properties. In the present work, a comparison of the hybrid effects of carbon black with two different nanofillers (graphene oxide and nanoclay) was studied. The 70/30 composition of chlorobutyl rubber/natural rubber elastomer blend was taken as per the blend composition optimized from our previous studies. The hybrid effects of graphene oxide and nanoclay in dispersing the nanofillers were studied mainly by analyzing nanocomposite barrier properties. The results confirm that the combined effect of carbon black with graphene oxide and nanoclay could create hybrid effects in decreasing the gas permeability. The prepared nanocomposites which partially replace the expensive chlorobutyl rubber can be used for tyre inner liner application. Additionally, the reduction in the amount of carbon black in the nanocomposite can be an added advantage of considering the environmental and economic factors.

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