Hot-Air Ageing Characteristics of Peroxide-Cured EPDM Rubber with 5-Vinyl-2-Norbornene as Third Monomer

The recently developed Keltan ACE technology enables the production of (very) high molecular-weight EPDM polymers with a variable amount of 5-vinyl-2-norbornene (VNB) as the third monomer. VNB-EPDMs have been evaluated in typical peroxide-cured, window gasket, engine mount and radiator hose formulations and have been compared with conventional Ziegler-Natta EPDM grades. In agreement with previous studies it is shown that the peroxide cross-linking efficiency ofthe VNB unsaturation is higher than those of ENB and DCPD, which allows a reduction of peroxide and co-agent dosages (window gasket: -30 %, engine mount: -50%) to reach the same state of cure. The hot- air heat ageing resistance of VNB-EPDM in the window gasket and engine mount formulations is shown to be similar or even better than those of the reference EPDM grades. The application of VNB-EPDM in the radiator hose formulation results in enhanced ageing resistance, which is believed to be an indirect consequence of the higher peroxide-curing efficiency of VNB-EPDM.