Microfluidic fabrication and thermal characteristics of core–shell phase change microfibers with high paraffin content

Abstract

We have developed a facile and controllable microfluidic strategy to fabricate core–shell phase change microfibers with high paraffin Rubitherm®27 (RT27) content. Coaxial core-sheath flows consisting of a cylindrical jet of melting RT27 (core fluid) and annular jet of poly(vinyl butyral) (PVB) solution (sheath fluid) are formed in a coaxial microdevice. With the core-sheath flows as templates, the phase change microfibers with core–shell structure are fabricated after solvent extraction. The RT27 content of microfibers is precisely controlled by simply adjusting the inner flow rate. The microstructures, thermal characteristics and mechanical strengths of microfibers are studied systematically by SEM, DSC, TGA and a tensile tester. The results show that the resultant microfibers are composed of RT27 core and PVB polymer shell which effectively prevents RT27 from leaking during the phase change process. The enthalpies of microfibers increase with the increase of RT27 content in microfibers. The maximum melting enthalpy and crystallization enthalpy of microfibers are about 128.2 J g−1 and 124.0 J g−1 respectively, and the corresponding encapsulation ratio is as high as 70%. The prepared phase change microfibers exhibit stable, repeatable and satisfactory thermal characteristics especially thermal-regulating property. The results provide valuable guidance for design and controllable preparation of phase change microfibers with advanced microstructures and satisfactory thermal characteristics.