Investigation of the properties of polynorbornene rubber/EPDM blends

Abstract

Polynorbornene rubbers (PNRs) used in this article were commercial compounds of polynorbornene filled with paraffin oil and fillers. The properties of PNR and ethylene-propylene-diene rubber (EPDM2650) blends with ratios of 100/0, 75/25, 50/50, 25/75, and 0/100 were investigated. Blends were cured by sulfur and accelerator at 150°C and 160°C, respectively. Moving die rheometer, differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and rubber process analyzer were used to examine the properties of the blends. The PNR exhibited significant reversion that was reduced by blending with EPDM. The thermal cross-linking of PNR occurred during hot air aging. The hot air aging resistance of PNR was improved by blending with EPDM. After 72 h of ozone aging, no obvious cracks were observed on the surface. The DMA results showed that the effective damping temperature range (tanδ ≥ 0.3) of vulcanized PNR was the broadest at 113°Cand then narrowed at higher temperature as the content of EPDM in the blend increased. With an increase in the ratio of EPDM, the glass transition temperature ( Tg) of EPDM moved to higher temperatures, as measured by DSC. The tensile strength of neat PNR is the greatest. PNR/EPDM = 75/25 blends showed yield behavior as the Tg of PNR moved to the higher temperature. These effects are attributed to a transfer of the extended oil from the PNR to the EPDM.