Molecular weight between physical entanglements in natural rubber: A critical parameter during strain-induced crystallization

Chenal, Jean-Marc; Chazeau, Laurent; Gallais, Laurent; Bomal, Y.; Gauthier, Catherine

doi:10.1016/j.polymer.2006.12.031

Cited by 113 publications

(114 citation statements)

References 22 publications

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“…84 As shown in Figure 13, crystallites size in the stretching direction (l 002 ) is rather constant during the whole cycle. 61 This was confirmed by Chenal et al 84 on NR samples having different network chain density (constant sulfur content, variable CBS content). The evolution of crystallites size along the two other directions is not so clear.…”

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confidence: 86%

“…The size of crystallites was measured by Trabelsi et al 61 along (002) direction corresponding to the stretching direction or along (200) and (120) directions by Tosaka et al 72 or along those three directions by Chenal et al 63,84 According to the latter authors, the dimensions of crystallites for a NR containing 1.5 phr sulfur and stretched at λ = 5 at room temperature are approximately: l 200 = 100 Å, l 120 = 30 Å and l 002 = 90 Å. 84 As shown in Figure 13, crystallites size in the stretching direction (l 002 ) is rather constant during the whole cycle. 61 This was confirmed by Chenal et al 84 on NR samples having different network chain density (constant sulfur content, variable CBS content).…”

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confidence: 99%

“…Now that we know more about SIC, the influence of other key parameters (depending on experimental conditions) is reviewed in the next section. The influence of crosslink density (ν, expressed in mol/cm 3 ) on SIC was studied by many authors 23,61,63,72,84 but it is still not entirely understood. The first interesting result is that the stretch ratio for onset of crystallization (λ A according to Figure 12) is almost unchanged with crosslink density, which is not so easy to admit considering the classical rubber elasticity theory.…”

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confidence: 99%

“…This reduction in size was confirmed by other studies in which it was also observed in the other directions. 23,63,84 This can be explained by considering that macromolecular chains are all the more shorten that crosslink density increases. Consequently, their ability to move in order to produce big crystallites is lowered.…”

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Strain-Induced Crystallization of Natural Rubber: A Review of X-Ray Diffraction Investigations

Huneau

2011

Rubber Chemistry and Technology

197

148

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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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confidence: 86%

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confidence: 99%

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Strain-Induced Crystallization of Natural Rubber: A Review of X-Ray Diffraction Investigations

Huneau

2011

Rubber Chemistry and Technology

197

148

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“…These changes are likely ar esult of more facile and rapid crystallization of the lower molar mass materials. [9] Thesynthetic nature of this system also affords the ability to control material properties via monomer design and endgroup modification. This method results in controllable and definable end groups that can be specifically modified and will be critical to dispersing and grafting fillers within the elastomer network.…”

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Independent Control of Elastomer Properties through Stereocontrolled Synthesis

Bell

Barker

et al. 2016

Angew Chem Int Ed

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In most synthetic elastomers,c hanging the physical properties by monomer choice also results in ac hange to the crystallinity of the material, which manifests through alteration of its mechanicalperformance.Using organocatalyzed stereospecific additions of thiols to activated alkynes,h igh-molarmass elastomers were isolated via step-growth polymerization. The resulting controllable double-bond stereochemistry defines the crystallinity and the concomitant mechanical properties as well as enabling the synthesis of materials that retain their excellent mechanical properties through changing monomer composition. Using this approacht oe lastomer synthesis,f urther end group modification and toughening through vulcanization strategies are also possible.The organocatalytic control of stereochemistry opens the realm to an ew and easily scalable class of elastomers that will have unique chemical handles for functionalization and post synthetic processing.Nature has evolved the ability to create large and complex molecules in which the precise control over the spatial arrangement of the atoms is critical to their performance.The three-dimensional control over the arrangement of bonds is as important to the function and behavior of molecules as any other factor and is critical to the structure-function relationships that govern the role of arange of molecules.While the effect of stereochemistry on functionality is probably best known in the examples of small molecule drugs such as thalidomide (one enantiomer is effective against morning sickness,t he other is teratogenic) or naproxen (one enantiomer is used to treat arthritis pain, the other causes liver poisoning with no analgesic effect), it is less well-studied with respect to materials design.Elastomeric materials are applied widely to demanding applications on account of their inherent reversible deformation behavior. Many synthetic elastomer materials are tri-or multi-block copolymers that are based on the concept of an amorphous-crystalline or hard-soft phase-separated system in which organization of the hard and soft domains endows the strong but elastic properties upon the materials.[1] While these materials have found widespread application, changes to the monomers or stoichiometry designed to elicit ac hange in physical properties also alter the chain packing and hence the mechanical properties of the materials.I nterestingly,n atural rubber and gutta percha are homopolymers of poly(cisisoprene) and poly(trans-isoprene) respectively.W hile these materials differ by only the double bonds of the backbone,the superior elastomeric properties of natural rubber [2] are attributed to the enhanced chain packing afforded by its stereochemical orientation.[3] While the design principles to control crystallinity and the associated mechanical properties in these materials are clear,the inability to incorporate awide range of functional groups in ac ontrolled manner or rationally define the chain end functionality limits the applications of both these materials a...

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