High and Very High Molecular Weight EPDM Polymers with 2-Vinyl-5-Norbornene As Third Monomer

The recently developed Keltan ACE technology enables the production of high and very high molecular weight EPDM polymers with up to ~3.5 wt% VNB as a third monomer. VNB-EPDMs have been evaluated in typical peroxide-cured, window gasket and engine mount formulations and compared with conventional Ziegler-Natta EPDM grades. In agreement with previous studies it is shown that the peroxide cross-linking efficiency of the VNB unsaturation is about 4 times higher than those of ENB and DCPD. This increased efficiency results in either higher cross-link densities at similar peroxide dosages, or in the same state of cure at much lower peroxide dosages (window gasket: -30%, engine mount: -50%). Finally, application of VNB-EPDM in a radiator hose formulation not only shows the high cross-linking efficiency, but also enhanced hot air ageing resistance. The very low level of residual unsaturation of the VNB-EPDMs after cross-linking was found to contribute significantly to the improved hot air ageing.