Reactive compatibilization of EPDM/PA6 blends with dicumyl peroxide: structure–property relationships

Abstract

In this study, binary blends based on ethylene–propylene–diene rubber (EPDM) and polyamide-6 (PA6) were systematically prepared with varying PA6 contents ranging from 10 to 40 phr. Dicumyl peroxide (DCP) was employed as a reactive compatibilizer in order to promote chemical linkages between the elastomeric and thermoplastic components and thereby enhance interfacial adhesion. The blending process was carried out in a Banbury internal mixer under controlled temperature and shear conditions, ensuring homogeneous distribution of the polyamide phase within the EPDM matrix, and the obtained compounds were subsequently compression molded to produce uniform test specimens.

The effect of increasing PA6 concentration on the physicomechanical, thermal, and morphological characteristics of the blends was extensively investigated. Tensile testing demonstrated that the incorporation of higher amounts of PA6 significantly increased tensile strength, modulus, and Shore hardness, which can be attributed to the reinforcing action of the rigid polyamide domains and the formation of peroxide-induced covalent interfacial linkages. Thermal gravimetric analysis further revealed an improvement in thermal stability with rising PA6 content, while differential scanning calorimetry and dynamic mechanical analysis indicated a gradual upward shift in storage modulus and in the glass transition behavior, consistent with the contribution of the stiff thermoplastic phase.

On the other hand, elongation at break and overall elasticity decreased as the PA6 fraction was raised, reflecting the stiffer and less deformable nature of the dispersed polyamide particles. Scanning electron microscopy (SEM) images confirmed that optimal phase dispersion and strong interfacial adhesion were obtained in blends containing approximately 20–30 phr PA6 together with 1.0–1.2 phr DCP. These particular formulations offered the best balance between mechanical strength, flexibility, and heat resistance. Overall, the results demonstrate that peroxide-compatibilized EPDM/PA6 blends possess tunable and application-oriented properties suitable for engineering uses where both mechanical robustness and thermal durability are simultaneously required.

Keywords: EPDM, PA6, reactive compatibilization, dicumyl peroxide, mechanical properties, thermal stability, morphology.