We investigated mechanocaloric properties of natural rubber and silicone rubbers in the shear mode of deformation using an in-house-made apparatus. A block-shaped sample was prepared by stacking eight to twelve pieces of 1-mm-thick rectangular sheet of rubber. The shear force <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$f$</EquationSource> <EquationSource Format="MATHML"><math> <mi>f</mi> </math></EquationSource> </InlineEquation> and temperature change <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\Delta T$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <mi>T</mi> </mrow> </math></EquationSource> </InlineEquation> of the sample were measured as it was deformed up to the shear value <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\gamma \approx 0.25$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>γ</mi> <mo>≈</mo> <mn>0.25</mn> </mrow> </math></EquationSource> </InlineEquation>. The temperature of the rubber increased at all values of the shear deformation in clear contrast to the extension experiment where the sample temperature decreases for small deformations. The stress and (the decrease of) the entropy density derived from the data were analyzed on the basis of the ideal rubber theory. The number densities of the partial chains derived from the shear force and from the entropy are consistent with each other for the natural rubber. But they are significantly different for the silicone rubbers: The number density of the partial chains calculated from the entropy is much smaller than those derived from the shear force for both of the two silicone rubbers. The reason for the discrepancy has not been known. Finally, comparison was made between the two components of the internal energy of rubber, i.e., the work and heat, involved in the shear deformation. For the natural rubber sample about 95% of the work done on the sample appeared as heat, indicating that it is nearly an ideal rubber. For the silicone rubbers, only 30–40% of the work spent on shear deformation was recovered as heat; the large part of the work done was stored in the rubber as its internal energy. Graphical abstract

Measurement of mechanocaloric effects in rubber in the shear mode of deformation

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2026年6月29日

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Daisuke Takajo,
Takasuke Matsuo

摘要

We investigated mechanocaloric properties of natural rubber and silicone rubbers in the shear mode of deformation using an in-house-made apparatus. A block-shaped sample was prepared by stacking eight to twelve pieces of 1-mm-thick rectangular sheet of rubber. The shear force $f$ $f$ and temperature change $\Delta T$ $Δ T$ of the sample were measured as it was deformed up to the shear value $\gamma \approx 0.25$ $γ \approx 0.25$ . The temperature of the rubber increased at all values of the shear deformation in clear contrast to the extension experiment where the sample temperature decreases for small deformations. The stress and (the decrease of) the entropy density derived from the data were analyzed on the basis of the ideal rubber theory. The number densities of the partial chains derived from the shear force and from the entropy are consistent with each other for the natural rubber. But they are significantly different for the silicone rubbers: The number density of the partial chains calculated from the entropy is much smaller than those derived from the shear force for both of the two silicone rubbers. The reason for the discrepancy has not been known. Finally, comparison was made between the two components of the internal energy of rubber, i.e., the work and heat, involved in the shear deformation. For the natural rubber sample about 95% of the work done on the sample appeared as heat, indicating that it is nearly an ideal rubber. For the silicone rubbers, only 30–40% of the work spent on shear deformation was recovered as heat; the large part of the work done was stored in the rubber as its internal energy.

Graphical abstract