Variation de la chaleur spécifique du caoutchouc en fonction de l'allongement

Mayor, Andre; Boissonnas, Ch. G.

doi:10.1002/hlca.19480310610

Cited by 8 publications

(5 citation statements)

References 15 publications

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“…It is defined by

C = - T {((), \frac{\partial^{2} normalΨ}{\partial T \partial T})}_{boldF, ξ_{α}} > 0

where Ψ is the free energy function. In unfilled natural rubber, volume changes are small[] and the specific heat does not vary significantly, even when crystallization occurs[]; therefore, the product ρ C can be assumed to be constant. The local form of the heat diffusion equation writes as follows:

ρ C \overset{T}{true} - Div false(κ_{0} Grad T false) = \underset{s}{\underset{⏟}{D_{i n t} + T \frac{\partial boldP}{\partial T} : \overset{F}{true} + T true \sum_{β = 1}^{m} \frac{\partial A_{β}}{\partial T} : \overset{ξ_{β}}{true}}} + R

where κ 0 is a positive semidefinite tensor characterizing the thermal conductivity of the material and s denotes the overall heat power density induced by the deformation process.…”

Section: Methodology For Crystallinity Measurementmentioning

confidence: 99%

“…where Ψ is the free energy function. In unfilled natural rubber, volume changes are small [23,24] and the specific heat does not vary significantly, even when crystallization occurs [25][26][27] ; therefore, the product C can be assumed to be constant. The local form of the heat diffusion equation writes as follows:…”

Section: Calorimetry Under Stretching: Thermodynamical Frameworkmentioning

confidence: 99%

See 1 more Smart Citation

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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“…It is defined by

C = - T {((), \frac{\partial^{2} normalΨ}{\partial T \partial T})}_{boldF, ξ_{α}} > 0

ρ C \overset{T}{true} - Div false(κ_{0} Grad T false) = \underset{s}{\underset{⏟}{D_{i n t} + T \frac{\partial boldP}{\partial T} : \overset{F}{true} + T true \sum_{β = 1}^{m} \frac{\partial A_{β}}{\partial T} : \overset{ξ_{β}}{true}}} + R

where κ 0 is a positive semidefinite tensor characterizing the thermal conductivity of the material and s denotes the overall heat power density induced by the deformation process.…”

Section: Methodology For Crystallinity Measurementmentioning

confidence: 99%

Section: Calorimetry Under Stretching: Thermodynamical Frameworkmentioning

confidence: 99%

Strain‐induced crystallization in rubber: A new measurement technique

Cam

2017

Strain

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“…In unfilled natural rubber, volume changes are small (Le Cam and Toussaint, 2008;Chenal et al, 2007) and the specific heat does not vary significantly, even when crystallization occurs (Vogt, 1937;Boissonnas, 1939;Mayor and Boissonnas, 1948), therefore the product ρC can be assumed to be constant. As the heat produced and absorbed due to thermomechanical s tmc couplings is the same, the temporal integration of Equation 5 over one mechanical cycle provides the energy due to intrinsic dissipation W intrinsic :…”

Section: Heat Power Densitymentioning

confidence: 99%

Energy storage due to strain-induced crystallization in natural rubber: The physical origin of the mechanical hysteresis

Cam

2017

Polymer

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International audienceStrain-induced crystallization is classically assumed to be responsible for the hysteresis loop observed in the mechanical response of cis-1,4-polyisoprene. The aim of the present study is to investigate where does this energy go. Energy balances carried out using infrared thermography have shown that the hysteresis loop is due neither to intrinsic nor thermal dissipation, but is entirely used by the material to change its microstructure. Thus, significant changes in the internal energy accompany SIC. Experiments performed show that the mechanical energy brought to deform the material is stored elastically in the amorphous phase (chain alignment and accumulation of topological constraints in the crystallite vicinity) and is released with a different kinetics during crystallite melting. The demonstration that NR is able to store mechanical energy without converting it into heat is a realistic way to explain its extraordinary resistance to crack growth. © 2017 Elsevier Lt

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“…In unfilled natural rubber, volume changes are small, i.e. ρ ¼ ρ 0 Toussaint 2008, Chenal, Gauthier, Chazeau, Guy, andBomal 2007), and the specific heat is assumed to not vary significantly, even when crystallization occurs (Vogt 1937, Boissonnas 1939, Mayor and Boissonnas 1948, therefore the product ρC can be assumed to be constant. τ is a parameter characterizing the heat exchanges between the specimen and its surroundings.…”

Section: Heat Source Reconstructionmentioning

confidence: 99%

A comparison between X-ray diffraction and quantitative calorimetry to evaluate the strain-induced crystallinity in natural rubber

Cam¹,

Albouy²,

Charlès³

2019

Constitutive Models for Rubber XI

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The crystallinity of stretched crystallizable rubbers is classically evaluated using X-ray diffraction (XRD). Recently, a measurement technique based on quantitative surface calorimetry from infrared thermography (IRT) has been proposed in Le Cam (2018), but results obtained were not compared with XRD measurements. In the present paper, the two measurement techniques are used for evaluating of the straininduced crystallinity of the same unfilled natural rubber. This study provides the first comparison between the two techniques. Results obtained highlight a very satisfactory agreement between the two measurements, which validates a new and simple way for evaluating the strain-induced crystallinity from temperature measurements.

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Variation de la chaleur spécifique du caoutchouc en fonction de l'allongement

Cited by 8 publications

References 15 publications

Strain‐induced crystallization in rubber: A new measurement technique

Strain‐induced crystallization in rubber: A new measurement technique

Energy storage due to strain-induced crystallization in natural rubber: The physical origin of the mechanical hysteresis

A comparison between X-ray diffraction and quantitative calorimetry to evaluate the strain-induced crystallinity in natural rubber

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