Elastocaloric effect dependence on pre-elongation in natural rubber

In the context of solid-state-cooling, the elastocaloric effect offers a very large controlled entropy change based in low-cost polymers, especially natural rubber which is environmentally friendly. However, large elastocaloric activity requires large elongation (>5), which makes this material im...

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Veröffentlicht in:Applied physics letters 2015-08, Vol.107 (8)
Hauptverfasser: Xie, Zhongjian, Sebald, Gael, Guyomar, Daniel
Format: Artikel
Sprache:eng
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Zusammenfassung:In the context of solid-state-cooling, the elastocaloric effect offers a very large controlled entropy change based in low-cost polymers, especially natural rubber which is environmentally friendly. However, large elastocaloric activity requires large elongation (>5), which makes this material impractical for cooling systems due to the large change in sample's area. By performing a pre-elongation, area change is limited, and β=−∂γ/∂λ (where γ is the specific entropy and λ is the elongation) is larger. The highest β value is obtained when pre-elongation is right before (at the “eve”) the onset of the strain-induced crystallization, which is also interpreted in the view of molecular conformation. Experimental results obtained on a natural rubber sample showed an adiabatic temperature change of 4.3 °C for pre-elongation of 4 with further elongation of 4 (true strain change of 69%). Furthermore, the entropy exhibits a quasi-linear dependence on elongation, and the β value is found to be 6400 J K−1 m−3.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4929395