Morphology of strain-induced crystallization of natural rubber. Part II. X-Ray studies on cross-linked vulcanizates

ABSTRACT Strain-induced crystallization (SIC) and stress–strain relations of varied crosslink structures and varied crosslink densities of vulcanized natural rubber (NR), vulcanized synthetic polyisoprene rubber (IR), and un-vulcanized natural rubber are compared using a synchrotron X-ray. The onset strain of SIC does not depend on crosslink density and crosslink structures. Un-vulcanized NR shows a smaller onset strain of SIC than that of vulcanized NR. Therefore, entanglements in NR are pivot points to induce SIC, just as entanglements in semi-crystalline plastics induce flow-induced crystallization (FIC). During deformation, complicated phenomena occur simultaneously such as cavitation, crosslink breakdown, SIC with temperature upturn, and limited extensibility of chains between crosslinks, because rubber is a significantly inhomogeneous material. It is still difficult to evaluate the contribution of SIC to stress-upturn of the stress–strain relation of rubber.

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The Orientation of Strain-Induced Crystallites in Uniaxially-Strained, Thin and Wide Bands Made from Natural Rubber

Crystals ◽

10.3390/cryst9060294 ◽

2019 ◽

Vol 9 (6) ◽

pp. 294 ◽

Cited By ~ 1

Author(s):

Konrad Schneider ◽

Matthias Schwartzkopf

Keyword(s):

Natural Rubber ◽

Pure Shear ◽

Orientation Distribution ◽

Thin Strip ◽

X Ray Diffraction ◽

Reinforcing Effect ◽

X Ray ◽

Crack Tips ◽

Strain Induced Crystallization ◽

Induced Crystallization

Vulcanized natural rubber (unfilled and filled with 20 phr carbon black) is strained. We suppress the macroscopic formation of fiber symmetry by choosing strip-shaped samples ("pure-shear geometry") and investigate the orientation of the resulting crystallites by two-dimensional wide-angle X-ray diffraction (WAXD), additionally rotating the sample tape about the straining direction. Indications of a directed reinforcing effect of the strain-induced crystallization (SIC) in the thin strip are found. In the filled material fewer crystallites are oriented and the orientation distribution of the oriented crystallites is less perfect. The results confirm, that it is important for the evaluation of crystallinity under deformation to check, whether fiber symmetry can be assumed. This has consequences in particular on the quantitative interpretation of space-resolved scanning experiments in the vicinity of crack tips. Furthermore it raises the question, whether there is an asymmetric reinforcing effect of the SIC in the vicinity of crack tips inside natural rubber.

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STRAIN-INDUCED CRYSTALLIZATION OF NATURAL RUBBER: A REVIEW OF X-RAY DIFFRACTION INVESTIGATIONS

Rubber Chemistry and Technology ◽

10.5254/1.3601131 ◽

2011 ◽

Vol 84 (3) ◽

pp. 425-452 ◽

Cited By ~ 106

Author(s):

Bertrand Huneau

Keyword(s):

Natural Rubber ◽

Mechanical Response ◽

Strain Curve ◽

Fatigue Properties ◽

X Ray Diffraction ◽

X Ray ◽

Strain Induced Crystallization ◽

Temperature Strain ◽

Kinetics Of ◽

Induced Crystallization

Abstract Strain-induced crystallization of natural rubber was discovered in 1925 by the means of x-ray diffraction and has been widely investigated by this technique until today. The studies devoted to the structure of the crystalline phase of natural rubber are first reviewed. This structure is strongly anisotropic and can be related to the exceptionally good strength and fatigue properties of this material. The relationships between strain-induced crystallization of natural rubber and its mechanical response, during static or tension-retraction tests, are also reviewed and discussed; in particular, the hysteresis of the stress-strain curve is mainly explained by strain-induced crystallization. The kinetics of crystallization under both static and cyclic deformation is also discussed, as well as the influence of different factors, depending either on material composition (crosslink density, carbon black fillers) or on external parameters (temperature, strain rate…).

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Crystal and Crystallites Structure of Natural Rubber and Synthetic cis-1,4-Polyisoprene by a New Two Dimensional Wide Angle X-ray Diffraction Simulation Method. I. Strain-Induced Crystallization

Macromolecules ◽

10.1021/ma400420k ◽

2013 ◽

Vol 46 (11) ◽

pp. 4520-4528 ◽

Cited By ~ 40

Author(s):

Justin Che ◽

Christian Burger ◽

Shigeyuki Toki ◽

Lixia Rong ◽

Benjamin S. Hsiao ◽

...

Keyword(s):

Natural Rubber ◽

Simulation Method ◽

Wide Angle ◽

Two Dimensional ◽

X Ray Diffraction ◽

X Ray ◽

Strain Induced Crystallization ◽

Induced Crystallization

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Strain-induced crystallization of carbon black-filled natural rubber during fatigue measured by in situ synchrotron X-ray diffraction

International Journal of Fatigue ◽

10.1016/j.ijfatigue.2012.07.001 ◽

2013 ◽

Vol 47 ◽

pp. 1-7 ◽

Cited By ~ 30

Author(s):

S. Beurrot-Borgarino ◽

B. Huneau ◽

E. Verron ◽

P. Rublon

Keyword(s):

Carbon Black ◽

Natural Rubber ◽

X Ray Diffraction ◽

X Ray ◽

Strain Induced Crystallization ◽

Induced Crystallization

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Strain-induced crystallization of natural rubber subjected to biaxial loading conditions as revealed by X-ray diffraction

Constitutive Models for Rubber VII ◽

10.1201/b11687-7 ◽

2011 ◽

pp. 23-28 ◽

Cited By ~ 5

Author(s):

S Beurrot ◽

B Huneau ◽

E Verron

Keyword(s):

Natural Rubber ◽

Biaxial Loading ◽

Loading Conditions ◽

X Ray Diffraction ◽

X Ray ◽

Strain Induced Crystallization ◽

Induced Crystallization

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Strain-induced crystallization of natural rubber as detected real-time by wide-angle X-ray diffraction technique

Polymer ◽

10.1016/s0032-3861(99)00724-7 ◽

2000 ◽

Vol 41 (14) ◽

pp. 5423-5429 ◽

Cited By ~ 166

Author(s):

S. Toki ◽

T. Fujimaki ◽

M. Okuyama

Keyword(s):

Natural Rubber ◽

Real Time ◽

Wide Angle ◽

X Ray Diffraction ◽

X Ray ◽

Strain Induced Crystallization ◽

Induced Crystallization

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

Rubber Chemistry and Technology ◽

10.5254/rct.19.81481 ◽

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.

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