Thermo-Mechanical Behavior of Novel EPDM Foams Containing a Phase Change Material for Thermal Energy Storage Applications

Abstract

In this paper Ethylene Propylene Diene Monomer rubber (EPDM) foams were filled with different amounts of paraffin, a common phase change material (PCM) having a melting temperature at about 70 °C, to develop novel rubber foams with thermal energy storage (TES) capabilities. Samples were prepared by melt compounding and hot pressing, and the effects of three foaming methods were investigated. In particular, two series of samples were produced through conventional foaming techniques, involving physical (Micropearl® F82, MP, Lehvoss Italia s.r.l. Saronno, Italia) and chemical (Hostatron® P0168, H, Clariant GmbH, Ahrensburg, Germany) blowing agents, while the salt leaching method was adopted to produce another series of foams. Scanning electron microscopy (SEM) and density measurements showed that MP led to the formation of a closed-cell porosity, while a mixed closed-cell/open-cell morphology was detected for the H foamed samples. On the other hand, foams produced through salt leaching were mainly characterized by an open-cell porosity. The qualitative analysis of paraffin leakage revealed that at 90 °C only the foams produced through salt leaching suffered from significant PCM leakage. Consequently, the thermo-mechanical properties were investigated only in samples produced with H and MP. Differential Scanning Calorimetry (DSC) analysis revealed that EPDM/paraffin foams were endowed by good TES properties, especially at higher PCM contents (up to 145 J/g with a paraffin amount of 60 wt%). Tensile and compressive tests demonstrated the addition of the PCM increased the stiffness at 25 °C, while the opposite effect was observed above the melting temperature of paraffin. These results suggest that the EPDM foams produced with H and MP show an interesting potential for thermal management of electronic devices.

Shape memory behavior of novel Ethylene Propylene Diene Monomer (EPDM)/paraffin foams

“…All the materials used for the foams’ production were the same as described in our previous work. [ 34 ] To summarize briefly, Exxon Mobil (Irving, TX) supplied the Vistalon® 2504 EPDM rubber. Vistalon® 2504 is an amorphous terpolymer with a broad molecular weight distribution and a Mooney viscosity (ML 1 + 4, 125°C) of 25 MU.…”

“…A sample of bulk EPDM rubber was also produced to compare the properties of foamed and un‐foamed samples. The procedure followed for the preparation of EPDM and EPDM/paraffin foams (schematized in Figure 1) was the same as reported in our previous work, [ 34 ] to which the reader is referred for further details.…”

“…As a result, during processing, gas bubbles are created in the viscous polymer matrix, which persists after cooling and creates a cellular structure. [ 34,37 ] The blowing agents can be subdivided into chemical and physical blowing agents. The first type is constituted of solid organic or inorganic chemicals that degrade thermally and release gases, while the second type is made up of fluids that evaporate and release gases to allow for polymer expansion.…”

“…The first type is constituted of solid organic or inorganic chemicals that degrade thermally and release gases, while the second type is made up of fluids that evaporate and release gases to allow for polymer expansion. [ 34,38 ]…”

“…In our previous work, [ 34 ] the thermal, mechanical, and TES properties of EPDM foams filled with paraffin (melting temperature 70°C) were investigated, demonstrating that expanded rubbers produced through conventional foaming techniques show an interesting potential for thermo‐insulating and thermal management applications. For example, they could be applied for the thermal management of electronic devices or pipe systems carrying fluids at temperatures close to 70°C and suffering from thermal fluctuations.…”