QUANTITATIVE ASSESSMENT OF THE BRANCHING ARCHITECTURE OF EPDM WITH HIGH CONTENT OF 5-VINYL-2-NORBORNENE AS THIRD MONOMER

The branching architecture of high-molecular-weight EPDM polymers with high amounts of 5-vinyl-2-norbornene (VNB) as a third monomer, produced using recently developed Keltan ACE (TM) technology, was assessed by means of the dilution rheology method proposed by Crosby et al.(1) and compared with conventional Ziegler-Natta EPDM grades. First, the dilution rheology results were converted into a single convenient parameter, called the dilution slope. Next, by combining the dilution rheology results with gel permeation chromatography data and assuming trifunctional branching points, we calculated the volume fraction of the branched polymer, the average molecular weight between branching points, and the branching density. It is shown that the high-VNB polymers studied contained a significantly higher amount of branch-on-branch structures.