Stress-Induced Crystallization Properties of Natural and Synthetic CIS-Polyisoprene

Trabelsi, Siwar; Albouy, Pierre‐Antoine; Rault, J.

doi:10.5254/1.3547825

Cited by 56 publications

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“…2,3 The higher T m of NR, not only in unstretched but also in stretched states, has been experimentally confirmed by Gent et al, 43 and recently by Trabelsi et al 42 Poompradub et al 44 further discussed this feature on the basis of the synchrotron WAXD studies for filled NR samples. They reported that the i values were also independent of the filler content, if the effective strain ratio of deformable rubber portion was taken into account.…”

Section: Incipient Strain Of Crystallizationmentioning

confidence: 73%

“…42,46,51 This fact indicates that the increase in crystallinity is due to the increased number of crystallites whose average size is constant. The crystallite size is slightly smaller for the samples with the larger .…”

Section: Morphological Featuresmentioning

confidence: 97%

“…By contrast, i was definitely different between the NR and IR samples; the i of IR samples was the larger (Figure 4; in this article, the larger number in the sample code indicates the smaller ). Toki et al 41 and Trabelsi et al 42 also showed that IR require the larger strain than NR to start SIC. According to Equation 6, the shift of i between NR and IR samples should be attributed to the difference in T m of unstretched samples, namely T m;1 .…”

Section: Incipient Strain Of Crystallizationmentioning

confidence: 99%

“…In the latter stage of SIC, the necessity to exclude Strain-induced Crystallization of NR the crosslinking from crystallizing molecular chains would retard the crystallization rate, and at the same time, would diminish the attainable crystallinity. 9,11,42 According to the new results, 50,51 we may have to reconsider the material design when we expect the reinforcing effect of SIC for quickly deformed products.…”

Section: Crystallization Under Constant Strainmentioning

confidence: 99%

“…Trabelsi et al 42 studied the distribution of the crystalline zone around crack tip. A crosslinked NR or IR sample with a notch was stretched to a predetermined strain ratio and fixed on a movable stage.…”

Section: Morphological Featuresmentioning

confidence: 99%

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Strain-Induced Crystallization of Crosslinked Natural Rubber As Revealed by X-ray Diffraction Using Synchrotron Radiation

Tosaka

2007

Polym J

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ABSTRACT:Strain-induced crystallization (SIC) of natural rubber (NR) has been extensively studied even before the advent of macromolecular physics. However, there are still some unsolved basic issues in this field. In this review article, classic studies on SIC of NR are briefly introduced, and then recent results by synchrotron X-ray diffraction studies in separate papers by different authors are categorized and interpreted on the basis of molecular models. Cyclic deformation experiments provided information on partial orientation of the network-chains, on nucleation and morphological changes of crystals and on stress field around the strain-induced crystals. On the other hand, experiments under constant strain provided information on kinetics of SIC, on stress relaxation due to SIC, and so on. The experimental results could be explained under the assumption that the SIC is dominated by strain, and that the crystals are of foldedchain type. However, in order to consistently explain the various experimental results, we have to establish a unified molecular model of the network structure. [doi:10.1295/polymj.PJ2007059] KEY WORDS Network-chain Density / Crosslinking / Supercooling / Entropy / Rubber Elasticity / Crystallite Size / Entanglement / Natural rubber (NR) from Hevea latex is an indispensable material for many industrial and household applications, 1 which is constituted of cis-1,4-polyisoprene (ca. 94%) and non-rubber components such as proteins (ca. 2%) and lipid (ca. 3%).2 The versatility of the plant-derived NR is mainly due to its outstanding tensile properties and the good crack growth resistance. We still cannot reproduce the good performance of the NR products using synthetic cis-1,4-polyisoprene rubber (IR). The superiority of NR has been thought to originate from its ability to crystallize immediately by expansion; by contrast, crystallinity of IR is not as high as NR because of the lower regularity of the main-chain structure. 2,3 In this context, straininduced crystallization (SIC) of NR has been extensively studied even before the advent of macromolecular physics.

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Section: Incipient Strain Of Crystallizationmentioning

confidence: 73%

Section: Morphological Featuresmentioning

confidence: 97%

Section: Incipient Strain Of Crystallizationmentioning

confidence: 99%

Section: Crystallization Under Constant Strainmentioning

confidence: 99%

Section: Morphological Featuresmentioning

confidence: 99%

See 3 more Smart Citations

Strain-Induced Crystallization of Crosslinked Natural Rubber As Revealed by X-ray Diffraction Using Synchrotron Radiation

Tosaka

2007

Polym J

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The tensile properties of strain‐crystallizing vulcanizates. II. Stress relaxation and hysteresis

Horst

McGill

Woolard

2006

J of Applied Polymer Sci

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Stress relaxation on cessation of extension and hysteresis were examined in conventional and peroxide vulcanizates over a range of crosslink densities at room temperature and at 90°C. The rate of relaxation decreases with an increase in temperature and is attributed to slower nucleation of strain-induced crystallites. The decrease in the volume fraction of extendable material as a result of straininduced crystallites has only a small effect on the rate at which the slope of the stress-strain curve rises. Crystallites that form on cooling, melt on heating, leaving an unaltered network, but when strain-induced crystallites are melted by heating, they do not reform on cooling. The relaxed network now extends further before failure than a network in which extension was not interrupted by a heating-cooling cycle. This supports proposals in the preceding article that straininduced crystals increase tensile properties by altering the network deformation pattern and not by the deflection of propagating flaws, whose mechanism would require the heated sample to fail earlier due to its lower crystalline content. Hysteresis increases sharply at strains at which crystallization in the network becomes possible. The hysteresis ratio reaches a plateau value at higher strains. Relaxation affects both the extension and retraction stress-strain curves and it is proposed that hysteresis is determined by differences in the crystallinity during extension and retraction.

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The tensile properties of strain‐crystallizing vulcanizates. III. The superiority of conventional over peroxide vulcanizates in terms of network microstructure

Horst

McGill

Woolard

2006

J of Applied Polymer Sci

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It is proposed that, when vulcanization is performed using peroxides, crosslinking leads to a simple network, whereas in conventional vulcanization crosslinking a partially interpenetrating polymer network (PIPN) is formed. Two unfilled polyisoprene networks of similar crosslink density, produced with dicumyl peroxide and 2-bisbenzothiazole-2,2Ј-disulfide/sulfur formulations, were compared with respect to the effect of strain rate on their stress-strain and hysteresis curves at room and elevated temperatures. At high elongations, the stress-strain curves for peroxide vulcanizates show a steeper upturn than for conventional vulcanizates, but have lower tensile strength and elongation at break. On increasing the extension rate, stress-strain curves for peroxide vulcanizates rise less steeply, while conventional vulcanizates rise more steeply. For both vulcanizates the hysteresis ratio decreases on increasing the rate at which samples are extended and retracted. The effect on conventional vulcanizates is less than on peroxide vulcanizates. It is suggested that chains in peroxide networks disengage increasingly rapidly at higher strains, allowing increased strain-induced crystallization. Rapid strain-induced crystallization leads to low ultimate tensile strength (UTS). In more complex PIPNs, the disengagement and alignment of chains are retarded. The increased nonuniform extension of chains promotes early strain-induced crystallization at low extensions, but overall it reduces the rate of crystallization, which occurs over a wider range of strains. This improves UTS and elongation.

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Stress-Induced Crystallization Properties of Natural and Synthetic CIS-Polyisoprene

Cited by 56 publications

References 0 publications

Strain-Induced Crystallization of Crosslinked Natural Rubber As Revealed by X-ray Diffraction Using Synchrotron Radiation

Strain-Induced Crystallization of Crosslinked Natural Rubber As Revealed by X-ray Diffraction Using Synchrotron Radiation

The tensile properties of strain‐crystallizing vulcanizates. II. Stress relaxation and hysteresis

The tensile properties of strain‐crystallizing vulcanizates. III. The superiority of conventional over peroxide vulcanizates in terms of network microstructure

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