Phase-change smart lines based on paraffin-expanded graphite/polypropylene hollow fiber membrane composite phase change materials for heat storage

Abstract In this paper, a series of novel flexible phase-change smart lines were fabricated by double encapsulating paraffin into polypropylene hollow fiber membranes (PPHFMs) and expanded graphite (EG) to overcome liquid leakage during phase transition and enhance thermal conductivity of paraffin. An available theoretical calculation method was developed to predict and evaluate the encapsulation ability of PPHFM. PPHFM after stretching 50% (PPHFM50) exhibited a considerable paraffin encapsulation capacity about 70.23 wt% (PP50-CPCM), and showed minimal impact on the phase change behavior of paraffin. PP50-CPCM was hence selected for injecting paraffin/expanded graphite to prepare phase-change smart lines (PEP-CPCMs) aiming at the high thermal conductivity and higher paraffin encapsulation capacity. The results indicated that the thermal conductivity of PEP-CPCMs with 2.08 wt% EG was obviously improved by 75%, and the maximum paraffin encapsulation capacity was 85.31 wt%. Moreover, the excellent thermal stability, thermal reliability and chemical compatibility of PEP-CPCMs were also confirmed. Interestingly, PEP-CPCMs were employed to twine the water cup (smart temperature adjustment cup). The results indicated that the flexible phase-change smart lines showed great potential in thermal energy storage applications.