scholarly journals Effect of crosslink density on the creep behavior of natural rubber vulcanizates

1966 ◽  
Vol 4 (5) ◽  
pp. 745-763 ◽  
Author(s):  
Donald J. Plazek
Keyword(s):  
Natural Rubber ◽  
Creep Behavior ◽  
Crosslink Density ◽  
Natural Rubber Vulcanizates

Kinetics of Crosslinking and Network Changes in Natural Rubber Vulcanizates with a Dithiodimorpholine Based Accelerator System

1980 ◽  
Vol 53 (5) ◽  
pp. 1015-1022 ◽  
Author(s):  
A. K. Bhowmick ◽  
S. K. De
Keyword(s):  
Natural Rubber ◽  
Rate Constants ◽  
Crosslink Density ◽  
Curing Temperature ◽  
Side Reactions ◽  
Filler Surface ◽  
Natural Rubber Vulcanizates ◽  
Kinetics Of ◽  
Accelerator System

Abstract Kinetics of crosslinking and network changes in unfilled and filled natural rubber vulcanizates with a dithiodimorpholine based accelerator system have been studied at 150° and 180°C. Results show that addition of HAF black enhances the polysulfidic crosslinks as well as the total crosslinks. This has been explained with the help of Coran's model wherein HAK black increases the rate constants. It is likely that the filler surface prevents desulfuration and undesirable side reactions involving the crosslink precursors. Increase of curing temperature by 30°C lowers the total crosslink density and increases the sulfur inefficiency.

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.

Pyrolysis-mass spectrometry correlations of crosslink density in natural rubber vulcanizates

1985 ◽  
Vol 9 (1) ◽  
pp. 19-28 ◽  
Author(s):  
Jacquelynn L. Savoca ◽  
Robert P. Lattimer ◽  
Joseph M. Richards ◽  
Willem Windig ◽  
Henk L.C. Meuzelaar
Keyword(s):  
Mass Spectrometry ◽  
Natural Rubber ◽  
Crosslink Density ◽  
Pyrolysis Mass Spectrometry ◽  
Natural Rubber Vulcanizates

Reinforcing Effect of Silica and Silane Fillers on the Properties of Some Natural Rubber Vulcanizates

2003 ◽  
Vol 76 (5) ◽  
pp. 1290-1310 ◽  
Author(s):  
A. Ansarifar ◽  
R. Nijhawan ◽  
T. Nanapoolsin ◽  
M. Song
Keyword(s):  
Natural Rubber ◽  
Crosslink Density ◽  
Cyclic Fatigue ◽  
Rubber Matrix ◽  
Stored Energy ◽  
Elongation At Break ◽  
Reinforcing Effect ◽  
Bound Rubber ◽  
Technical Properties ◽  
Natural Rubber Vulcanizates

Abstract The reinforcing effect of up to 6 parts per hundred rubber by weight (phr) bis- (3-triethoxysilylpropyl) tetrasulfide (TESPT), a bifunctional organosilane, on the crosslink density, bound rubber, and technical properties of some conventional accelerator/sulfur compounds of natural rubber, containing 30 phr precipitated amorphous white silica was studied. The crosslink density and bound rubber improved as a function of TESPT loading. The tensile strength, elongation at break, stored energy density at rupture, and cohesive tear strength deteriorated at low loading of TESPT, but they subsequently increased after the full amount of TESPT was introduced into the compound. The improved properties of the vulcanizate was due to the better dispersion of the filler in the rubber matrix. However, the cyclic fatigue life was adversely affected, and the hardness hardly changed as a result of adding TESPT to the rubber.

EFFECT OF CURE EFFICIENCY ON PROPERTIES OF GUM AND BLACK FILLED NATURAL RUBBER VULCANIZATES

2011 ◽  
Vol 84 (2) ◽  
pp. 229-242 ◽  
Author(s):  
Gary R. Hamed ◽  
Kanoktip Boonkerd
Keyword(s):  
Electron Microscopy ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Crosslink Density ◽  
Cure Time ◽  
Cracking Pattern ◽  
Natural Rubber Vulcanizates ◽  
Scanning Electron ◽  
Fracture Specimens ◽  
Strength Effect

Abstract Effects of the sulfur cure efficiency on the reversion behavior and the normal and edge-cut tensile strength of gum and black filled natural rubber (NR) vulcanizates were studied. N, N-dicyclohexyl-2-benzothiazole sulfenamide (DCBS) was used as an accelerator. A series of five vulcanizates with high to low cure efficiencies was prepared by increasing the sulfur (S) to DCBS ratios within the range of 0.26–6.66. All vulcanizates were formulated to have the same crosslink density. The degree of reversion (%) calculated from cure curves of gum and black filled NR at 20 min above the cure time (tc100) passed through maximum with decreasing cure efficiencies. For both gum and black filled NR, the highest degree of reversion (%) was observed at the S/DCBS ratio of 1.17. The normal tensile strengths of gum and black filled NR were directly proportional to the cure efficiency. For gum NR vulcanizates, the edge-cut tensile strength was markedly influenced by cure efficiency. Similar to the normal tensile strength, the gum NR vulcanizates cured with the lowest cure efficiency showed the lowest edge-cut tensile strength. Effect of the cure efficiency on the edge-cut tensile strength was less in the case of black filled NR vulcanizates. However, the black filled NR vulcanizates cured with the lowest cure efficiency also showed the lowest edge-cut tensile strength. The cut tip characteristics of the fracture specimens were investigated using scanning electron microscopy. The gum specimens showed only the simple lateral cracking pattern, while all black filled specimens showed the longitudinal cracking pattern. Four different cracking patterns of the black filled specimens were identified. The distribution of cracking patterns depended strongly on the size of precut and the cure efficiency.

Effect of Crosslink Density on Cut Growth in Gum Natural Rubber Vulcanizates

2002 ◽  
Vol 75 (2) ◽  
pp. 323-332 ◽  
Author(s):  
G. R. Hamed ◽  
N. Rattanasom
Keyword(s):  
Natural Rubber ◽  
Crosslink Density ◽  
Rough Fracture ◽  
Test Pieces ◽  
Loading Direction ◽  
Crosslinked Networks ◽  
Cut Depth ◽  
Natural Rubber Vulcanizates ◽  
Crack Contour ◽  
Unusual Increase

Abstract Conventional sulfur-cured, gum natural rubber vulcanizates of various crosslink densities were prepared. Dumbbell test pieces with and without edge precuts were tested in uniaxial tension. Relative strengths of the different vulcanizates depended on cut size. Lightly crosslinked specimens exhibited an abrupt drop in strength at a critical cut size, ccr, which became smaller as crosslink density increased because of reduced strain crystallizability. At all cut depths, crack growth was simply perpendicular to the loading direction and crack surfaces were smooth. A moderately crosslinked composition exhibited crack deviation prior to rupture. This was associated with an unusual increase in strength with increasing cut size. Densely crosslinked networks exhibited lateral fracture, like the lightly crosslinked gums, but produced a jagged crack contour path reflective of a rough fracture surface. Moreover, for the highly crosslinked samples, a critical cut size was not found. Rather, log-log plots of strength versus cut depth were linear and had slopes slightly greater than minus one-half.

Creep and Stress Relaxation of Natural Rubber Vulcanizates. Part I. Effect of Crosslink Density on the Rate of Creep in Different Vulcanizing Systems

1971 ◽  
Vol 44 (3) ◽  
pp. 707-720
Author(s):  
E. D. Fairlie
Keyword(s):  
Creep Rate ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Chemical Treatment ◽  
Crosslink Density ◽  
Strong Dependence ◽  
Viscoelastic Behavior ◽  
Creep And Stress Relaxation ◽  
Natural Rubber Vulcanizates ◽  
Determining Factor

Abstract The physical creep of unfilled natural rubber vulcanizates, prepared with different vulcanizing systems, has been studied. For each of the three vulcanizing systems chosen there is a strong dependence of creep rate on crosslink density, but the rates for accelerated sulfur vulcanizates are two or three times higher than those of peroxide vulcanizates of similar crosslink density. Supplementary experiments, in which the crosslink structure of sulfur vulcanizates is modified either by chemical treatment or by variations in the vulcanizing conditions, show that the nature of the crosslink itself is not a determining factor in the type of vulcanizate. Other features, such as the type and quantity of extranetwork material arising from the vulcanizing process, contribute significantly to the viscoelastic behavior of accelerated sulfur vulcanizates.

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