Long Chain Branching in EPDM Polymers. An Open Door to a Complete Spectrum of Mooney viscosity-Molecular Weight Relationships

摘要

Mooney viscosity is one of the parameters used to specify EPDM polymers along with the ethylene content and ENB level; Mooney viscosity is often understood as being directly correlated with the polymer molecular weight and is commonly used to select products with regards to compound processability and mechanical property performance. Historically, these rules of thumb had been developed through experience with polymers made with traditional vanadium catalyst technologies in that branching was not a key variable of design. Recent advancements in molecular catalysts and production technology allow the statistical and homogeneous incorporation of long chain branches. As a result of this development, the rheological behavior as well as the physical properties of an EPDM polymer for a given Mooney viscosity depend on the combination of the polymer's molecular weight and long chain branching. In this paper, we explored the effect of long chain branching on the mixing and processing of EPDM, and how defined long chain branching architectures enabled the access to a complete spectrum of Mooney viscosity-molecular weight relationships beyond the traditional correlations for linear polymers.