Influence of graphite nano powder on ethylene propylene diene monomer/paraffin wax phase change material composite: Shape stability and thermal applications

Abstract

In present research, ethylene propylene diene monomer (EPDM) impregnation in liquid paraffin wax (PW) phase change material (PCM) has been accomplished for PCM shape stabilization which is of great importance in various thermal energy storage applications. Otherwise stated, EPDM rubber was mixed with specific amount of Benzoyl peroxide as a crosslink agent using two-roll mill along with hot press at 160 °C for 15 min and subsequently graphite nano powder was added to enhance extremely low PCM thermal conductivity. Afterwards, fabricated EPDM/Graphite composites have been impregnated in melted PW PCM at 120 °C for 24 h. Findings have demonstrated that, by graphite percentage increment, EPDM cross-links amount has been declined and as a consequence, swelling rate along with PW PCM content has been increased. As expected, 20 wt% graphite addition to EPDM matrix has led to thermal conductivity increment by 120 %. In addition, for all EPDM/Graphite/PW PCM composite systems, leakage amount was <1 % which is desirable for thermal energy storage applications. Furthermore, according to swelling and leakage findings, EPDM/Graphite/PW PCM composite which contains 72.5 wt% PW (EWG24), was selected as an adequate system and thermal analysis results have shown that EWG24 had highest phase change enthalpy with suitable thermal efficiency improvement (45 %). Finally, Time-Temperature history analysis has depicted that EWG24 optimum system had 28 % further heat storage compared to its corresponding EG24 composite. Ultimately, performance time has been improved by 60 % compared to graphite-free PCM system, which makes EPDM/PW PCM/Graphite composite an adequate candidate for various thermal storage applications.