Giant Reversible Barocaloric Effects in Nitrile Butadiene Rubber around Room Temperature

Abstract

Elastomers have shown to be promising barocaloric materials, being suitable candidates for solid-state cooling devices. Moreover, this family of polymers presents additional advantages, such as their low cost and long fatigue life. In this context, we investigated the barocaloric effects in Nitrile Butadiene Rubber (NBR) in a large range around room temperature. Moderated applied pressures on NBR yield giant temperature change ({\Delta}TS) and entropy change ({\Delta}ST), reaching the maximum values of 16.4(2) K at 323 K and 59(6) J kg-1K-1 at 314 K, respectively, for a pressure change of 390 MPa. Besides, both {\Delta}TS and {\Delta}ST have shown to be rather reversible. An influence of the glass transition on the barocaloric effects was verified: the glassy state tends to diminish the entropy and temperature changes in comparison with the rubbery state. Furthermore, we calculated the pressure coefficient of glass transition (dTg/dP) obtained from different processes. Our study evidences the potential of NBR for cooling applications based on barocaloric effect, but also points out the glass transition must be avoided for a better barocaloric performance.