Influence of silica fillers on the ageing by gamma radiation of EDPM nanocomposites

Abstract

Abstract:This study evidences that the presence of silica fillers as well as their surface treatment influences the impact of gamma irradiation on the mechanical properties of the filled materials. It influences it both chemically, by a modification of the kinetics of the degradation reactions, and physically, through the complex modification of the filler-filler and fillermatrix interactions involved in the mechanical properties of the filler network.

Role of temperature during ageing under gamma irradiation of filled EPDM: consequences on mechanical properties

“…As reported in reference,17 because the polymer phase of this composite is less crosslinked, irradiation at 25 °C, leads also to a slight crosslinking phenomenon at the beginning of irradiation. However, after 50 kGy, the main occurring process is chain scission.…”

“…The curing time ( t 98 at 170 °C) is previously estimated from torque measurement performed with a MOSANTO analyzer; it is the time needed to obtain 98% of the maximum torque; it is chosen equal to 10 min for unfilled EPDM and ATH‐filled EPDM, and to 5 min for silica‐filled EPDM. In the previous study,17 it has been shown that the polymer phase of this composite is slightly less crosslinked than the unfilled material.…”

“…Thus, crosslinking takes place during thermo‐oxidation at 80 °C like in the case of the unfilled polymer. But the Q decrease for the silica‐filled material is more important since it leads to the same value at high dose although it begins from a higher value in the unaged state (Indeed, for processing reason, E‐SiU is initially slightly less crosslinked than E‐CR17). This suggests that the crosslinking process is more important in E‐SiU, probably because the material is initially farther from its maximum possible crosslinking density.…”

“… At room temperature (the water temperature of the pool was around 18 °C) for doses 50, 165, 300, 510 kGy. At this temperature, these materials are semi‐crystalline with a crystallinity ratio of ∼11% 15–17 At 80 °C for doses 50, 165, and 300 kGy.…”

“…It is noteworthy that literature on the impact of the filler on the material properties degradation is very scarce. In previous works,13, 14, 16, 17 EPDM rubbers with simplified formulation (no antioxidant, specific peroxide, no help processing additives) and with and without fillers (ATH or silica) have been aged by gamma radiation at room temperature under oxygen atmosphere to study the role of the fillers in the material aging. It was found that even if the polymer phase is degraded by the same degradation mechanisms, the filler presence induces particular phenomena.…”