Mechanisms of deformation in crystallizable natural rubber. Part 1: Thermal characterization

Martinez, Jose Ricardo Samaca; Cam, Jean‐Benoît Le; Balandraud, Xavier; Toussaint, Evelyne; Caillard, Julien

doi:10.1016/j.polymer.2013.03.011

Cited by 66 publications

(35 citation statements)

References 29 publications

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“…When the applied strain was removed, the temperature decreased below room temperature and then increased exponentially back to room temperature. The temperature decrease is larger than the temperature increase, which is caused by different kinetic properties of SIC and melting [6,26,29,30], as discussed in a previous paper [6]. SIC requires time to be completed (up to several minutes) which is much longer than the adiabatic limit.…”

Section: Methodsmentioning

confidence: 95%

Fatigue effect of elastocaloric properties in natural rubber

Sebald¹,

Xie²,

Guyomar³

2016

Phil. Trans. R. Soc. A.

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In the framework of elastocaloric (eC) refrigeration, the fatigue effect on the eC effect of natural rubber (NR) is investigated. Repetitive deformation cycles at engineering strain regime from 1 to 6 results in a rapid rupture (approx. 800 cycles). Degradation of properties and fatigue life are then investigated at three different strain regimes with the same strain amplitude: before onset strain of strain-induced crystallization (SIC) (strain regime of 0-3), onset strain of melting (strain regime of 2-5) and high strain of SIC (strain regime of 4-7). Strain of 0-3 leads to a low eC effect and cracking after 2000 cycles. Strain of 2-5 and 4-7 results in an excellent crack growth resistance and much higher eC effect with adiabatic temperature changes of 3.5 K and 4.2 K, respectively, thanks to the effect of SIC. The eC stress coefficient index γ (ratio between eC temperature change and applied stress) for strains of 2-5 and 4-7 are γ2-5=4.4 K MPa(-1) and γ4-7=1.6 K MPa(-1), respectively, demonstrating the advantage of the strain regime 2-5. Finally, a high-cycle test up to 1.7×10(5) cycles is successfully applied to the NR sample with very little degradation of eC properties, constituting an important step towards cooling applications.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

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Section: Methodsmentioning

confidence: 95%

Fatigue effect of elastocaloric properties in natural rubber

Sebald¹,

Xie²,

Guyomar³

2016

Phil. Trans. R. Soc. A.

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“…The methodology proposed for measuring crystallinity is now applied to experimental data issued from the literature. Here, data given in other literature[] are used. They were obtained with an unfilled natural rubber submitted to cyclic uniaxial tensile loading.…”

Section: Application To An Unfilled Natural Rubbermentioning

confidence: 99%

Strain‐induced crystallization in rubber: A new measurement technique

Cam

2017

Strain

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The crystallinity of stretched crystallizable rubbers is classically investigated using X-ray diffraction. In this study, we propose a new method based on temperature measurement and quantitative calorimetry to determine rubber crystallinity during mechanical tests. For that purpose, heat power density are first determined from temperature variation measurements and the heat diffusion equation. The increase in temperature due to strain-induced crystallization is then deduced from the heat power density by subtracting the part due to elastic couplings. The heat capacity, the density, and the enthalpy of fusion are finally used to calculate the crystallinity from the temperature variations due to strain-induced crystallization. The characterization of the stress-strain relationship and the non-entropic contributions to rubber elasticity is not required.This alternative crystallinity measurement method is therefore a user-friendly measurement technique, which is well adapted in most of the mechanical tests carried out with conventional testing machines. It opens numerous perspectives in terms of high speed and full crystallinity field measurements.

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“…NR undergoes strain‐induced crystallization (SIC) that is the rapid development of crystallization under straining. Many aspects of SIC have been reviewed, and further works are continuously appearing, focused on the study of models, crystallite structure, segmental dynamics, local strain response, mechanism of deformation, morphology, orientation and deformation mechanisms, crystallite melting temperature, temperature dependence of the mechanical properties, kinetics and time of crystallization, fatigue behavior, effect of entanglements and endlinking networks, and deproteinization . Some conclusions are widely acknowledged.…”

Section: Introductionmentioning

confidence: 99%

Crystallinity and crystalline phase orientation of poly(1,4-cis-isoprene) fromHevea brasiliensisandTaraxacum kok-saghyz

Musto

Barbera

Maggio

et al. 2016

Polym. Adv. Technol.

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Crystallization is studied for poly(isoprene-1,4-cis) from Hevea brasiliensis (natural rubber [NR]) and from taraxacum kok-saghyz, mainly by collecting wide-angle X-ray diffraction patterns after processing and stretching. Although rubber samples before stretching are generally fully amorphous, crystallization can be induced in NR samples by processing at room temperature under moderate pressure. This phenomenon is possibly associated with nucleation by saturated fatty acid components. For rubber samples being fully amorphous in the undeformed state, straininduced crystallization occurs only at high strain ratios (α > 4), leading to high degrees of crystalline phase orientation (f c > 0.9 for α = 5). Rubber samples presenting some crystallinity already in the unstretched state, on the contrary, reach much lower degrees of axial orientation, even for high strain ratios (f c < 0.7 for α = 5). These differences in crystallinity and in crystalline phase orientations produce large differences in stress-strain behavior of the rubber. By room temperature processing, the considered NR samples can also develop an unreported disordered crystalline modification, with low intensity of 120 and 121 reflections. This disordered crystalline modification, which is also maintained after axial stretching procedures, can rationalized by a structural disorder along the b axis, possibly associated with statistical sequences of A + TA À or A À T A + conformations for poly(isoprene-1,4-cis) chains. Copyright © 2016 John Wiley & Sons, Ltd.Keywords: poly(isoprene-1,4-cis); crystallinity; strain-induced crystallization INTRODUCTIONNatural rubber (NR) is the regular head-to-tail polymer essentially made by isoprene-1,4-cis units. [1][2][3][4] It is the most important rubber, with increasing worldwide consumption, that amounts at present to more than 12 million t/year.[5] At the origin of such a large commercial success are the NR outstanding properties: great strength [6,7] and tack [8][9][10] in the uncrosslinked state and in the crosslinked state, very high tensile strength [11,12] and crack growth resistance, both in static [13][14][15][16][17] and in fatigue [18][19][20][21][22][23][24] loading conditions. Beneficial for such NR properties is definitely the great mobility of the polymer chains that are usually amorphous at rest. However, also the ability of NR to crystallize plays a fundamental role. NR undergoes strain-induced crystallization (SIC) that is the rapid development of crystallization under straining. Many aspects of SIC have been reviewed, [25][26][27] and further works are continuously appearing, focused on the study of models, [28,29] crystallite structure, [30,31] segmental dynamics, [32] local strain response, [33] mechanism of deformation, [34] morphology, [35] orientation and deformation mechanisms, [36] crystallite melting temperature, [37] temperature dependence of the mechanical properties, [38] kinetics [36,39,40] and time [41] of crystallization, fatigue behavior, [42,43] effect of entanglements and endlinking n...

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Mechanisms of deformation in crystallizable natural rubber. Part 1: Thermal characterization

Cited by 66 publications

References 29 publications

Fatigue effect of elastocaloric properties in natural rubber

Fatigue effect of elastocaloric properties in natural rubber

Strain‐induced crystallization in rubber: A new measurement technique

Crystallinity and crystalline phase orientation of poly(1,4-cis-isoprene) fromHevea brasiliensisandTaraxacum kok-saghyz

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