Organic reinforcement of an ethylene propylene diene monomer with the in situ synthesis of a polyimide dispersed phase by reactive extrusion

Abstract Ethylene‐propylene‐diene monomer rubber, grafted with maleic anhydride functions (EPDM‐g‐MA) was organically reinforced by reactive extrusion from the in situ synthesis of a polyimide (PI) phase. The blends were reactively processed at 200°C in a twin‐screw extruder, with the PI content varying from 5 to 40 wt%. Transmission Electron Microscopy (TEM) revealed a very fine nodular dispersion of the PI phase with diameters ranging from 130 to 240 nm depending on the PI concentration. The reinforcement of the elastomer was evidenced with a sharp increase of the Young's modulus and the tensile strength, and the stiffness of the material was further increased with the PI content. The linear viscoelastic regime, as measured by the variation in storage modulus as a function of strain, was unaffected by this organic reinforcement, thus opening up an original way of controlling the Payne effect. Additionally, the cross‐linking of the blend with 20 wt% of PI with dicumyl peroxide (DCP) showed that the PI phase did not impact the creation of the cross‐linked network. The decrease of the swelling ratio and the improvement of the elastic recovery suggested that EPDM‐g‐PI copolymers can create a second network in the material, resulting in a higher apparent cross‐linking density. The mechanical properties of the cured blend showed a doubling of the Young's modulus and maximal stress values compared to those obtained for the pure matrix as well as a constant strain at break. Highlights Ethylene‐propylene‐diene monomer rubber, grafted with maleic anhydride functions (EPDM‐g‐MA) was organically reinforced by reactive extrusion. The reinforcement was obtained from the in situ synthesis of a polyimide (PI) phase. The Young's modulus of cross‐linked EPDM containing 20 wt% PI was doubled. The linear viscoelastic regime was unaffected by this organic reinforcement. This original way of reinforcement opens the control of the Payne effect.