Research on the stress softening of vulcanized natural rubber with different hardness

2021 ◽  
Author(s):  
Kewei Tong ◽  
Qian Li ◽  
Kai Jiang
Keyword(s):  
Natural Rubber ◽  
Stress Softening

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 STRAIN-INDUCED CRYSTALLIZATION ON STRESS SOFTENING OF SULFUR CROSS-LINKED UNFILLED GUAYULE AND DANDELION NATURAL RUBBERS

2019 ◽  
Vol 92 (2) ◽  
pp. 388-398
Author(s):  
P. Junkong ◽  
Y. Matsushima ◽  
T. Phakkeeree ◽  
K. Cornish ◽  
Y. Ikeda
Keyword(s):  
Natural Rubber ◽  
Cyclic Deformation ◽  
X Ray Diffraction ◽  
Key Factors ◽  
Average Volume ◽  
X Ray ◽  
Stress Softening ◽  
Strain Induced Crystallization ◽  
Stretching Ratio ◽  
Induced Crystallization

ABSTRACT The stress softening behaviors of sulfur cross-linked unfilled guayule natural rubber (S-GR) and sulfur cross-linked unfilled dandelion natural rubber (S-DR) under cyclic deformation were characterized by simultaneous wide angle X-ray diffraction and tensile measurements under cyclic deformation. The behaviors were found to be affected by their strain-induced crystallization (SIC) phenomena and aggregated nonrubber components. The stress softening degree at stretching ratio = 8.0 of S-DR was almost two times larger than that of S-GR. Additionally, the hysteresis loss and residual strain of S-DR were much higher than those of S-GR in the same cycle. The key factors that caused the increase in their degree of stress softening were the increase in average volume and the decrease in average number of strain-induced crystallites upon cyclic deformation, not the insignificant decrease in crystallinity. The breakage of the aggregated nonrubber components is a main origin of stress softening behaviors for S-GR and S-DR because their SIC behaviors also were significantly influenced by the aggregates of nonrubber components in the rubber matrixes. Both the effects of nonrubber components and SIC on stress softening were more dominant in S-DR than in S-GR, probably owing to the larger amount of aggregated nonrubber components in the former than in the latter. The results will be useful in effectively using guayule and dandelion natural rubbers as alternatives to Hevea natural rubber in the rubber industry.

Stress Softening in Natural Rubber Vulcanizates. Part II. Stress Softening Effects in Pure Gum and Filler Loaded Rubbers

1966 ◽  
Vol 39 (4) ◽  
pp. 814-822 ◽  
Author(s):  
J. A. C. Harwood ◽  
L. Mullins ◽  
A. R. Payne
Keyword(s):  
Natural Rubber ◽  
Effective Strain ◽  
Hysteresis Loops ◽  
Local Orientation ◽  
Stress Strain ◽  
Stress Softening ◽  
Rubber Phase ◽  
Softening Process ◽  
Natural Rubber Vulcanizates

Abstract Considerable stress softening occurs in both gum and filler-loaded vulcanizates and when compared at the same stress the extent of softening is similar in both gum and filled vulcanizates. It thus appears that the softening process is mainly due to the rubber phase alone. Apparent differences between the stress—strain hysteresis loops of gum and filler-loaded vulcanizates are traced to an increase in the effective strain in the rubber phase resulting from the presence of black. This is discussed in Part I of this series. The mechanism of stress softening in gum vulcanizates is not well understood. Possible sources include (1) breaking and remaking of crosslinks during extension, (2) residual local orientation of network chains persisting after recovery, and (3) breaking of network chains.

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.

Cyclic uniaxial mechano optical studies on stress-softening behavior of natural rubber/clay nanocomposites

Polymer ◽  
2019 ◽  
Vol 169 ◽  
pp. 52-57 ◽  
Author(s):  
Yurong Liang ◽  
Yingjie Tan ◽  
Yuanhao Guo ◽  
Mingzheng Hao ◽  
Tao Zhang ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Clay Nanocomposites ◽  
Optical Studies ◽  
Stress Softening ◽  
Softening Behavior
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