Rheological study of EPDM/silicone rubber blends phase inversion and characterization of resultant mechanical and thermal properties

This study was committed to the characterization of the rheological, thermal, mechanical, and morphological properties of ethylene-propylene-diene monomer (EPDM)/silicone rubber (SR) blends. These blends are a potential new class of materials for the insulation of circuits and electrical components that actuate in environments with high heat generation. The blends were produced in a torque rheometer with a Banbury type rotor, varying the concentration of EPDM and SR. Results obtained by capillary rheometry were applied to three theoretical models to analyze the phase inversion threshold, which was confirmed by scanning electron microscopy images. Such analyzes were important to describe the consequence of phase inversion on the evaluated properties. It was reported that the increase in SR concentration decreased the elastic modulus and increased the tensile strength of the blends. For blends with composition situated after phase inversion, the SR becomes the matrix, leading to a significant rise in the Vicat softening temperature and reduced thermal conductivity. Such improvements extend the range of applications of these materials as electrical insulators in environments with higher heat generation.