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

Abstract

Ethylene Propylene Diene Monomer (EPDM) rubber foams are widely employed for thermal and acoustic insulation in building construction. However, their installation in confined spaces is often complicated, and the capability of EPDM foams to exhibit shape memory behavior could be a desirable property. In the literature, several works have demonstrated that blending elastomeric matrices with paraffin, a well-known Phase Change Material (PCM), could be an interesting method to obtain shape memory polymers with a tunable switching temperature. In this work, EPDM foams filled with paraffin wax, having a melting temperature of 70°C, were produced and characterized from a microstructural and thermo-mechanical point of view. By melt compounding and hot pressing, samples were produced, and the PCM content in the foams was varied between 0 and 60 wt% (with respect to the EPDM matrix). The results of the shape memory tests evidenced the crucial role played by the PCM in providing excellent shape fixability for the expanded rubber. Even a limited amount of paraffin (i.e., 20 wt%) was able to raise the strain fixity parameter to a value higher than 80%, and it reached 100% when the paraffin content was increased to 60 wt%. On the other hand, an increased PCM fraction caused a slower recovery process. Consequently, a compromise between a fast recovery and optimum shape fixability should be accepted. These results are promising for the development of novel thermal and acoustic EPDM insulating foams easier to be installed.