Additive manufactured thermoplastic elastomers for low-stress driven elastocaloric cooling

Abstract

Exploiting the strain-induced crystallization of soft elastomeric polymers elastocaloric cooling has recently been explored as an environmental-friendly alternative to conventional refrigeration. Elastomers require a much lower applied stress to induce the elastocaloric effect compared to shape memory alloys. Several prototype coolers employing these soft polymers have been demonstrated to achieve a moderate temperature span under lower stresses. Here, we investigate the elastocaloric properties and potential cooling performance of five thermoplastic elastomers that can be 3D printed, both in the form of filaments and as Additive Manufactured (AM) parts. The materials were first characterized as filaments to screen for the elastomers with the highest elastocaloric effects. A large adiabatic temperature change of 17.8 K was obtained in the Ultimaker98A filament. AM parameters were optimized to achieve parts with satisfactory functional stability while maintaining their elastocaloric effect. As a printed part, NinjaFlex achieved a high material coefficient of performance (COPmat) of 3.2 with 1.74 J/g input work at ∼0.1 Hz, driven by a stress of 5.7 MPa. Implementing AM elastocaloric elastomers creates opportunities for the development of full-scale low-activation-stress regenerative elastocaloric cooling components that enable optimizing flow structures and enhanced heat-transfer performance.