Long Chain Branching in EPDM Resins. an Open Door to a Complete Spectrum of Mooney-Molecular Weight Relationships

Mooney viscosity is one of the parameters used to specify EPDM resins along with the ethylene and ENB composition; the understanding of Mooney viscosity and its relationship to polymer molecular weight is often used to select resins for compound processability and mechanical property performance.  Historically, these viscosity relationships have been developed with a prevalence of resins made with traditional vanadium catalyst technology in which branching was not a key variable of design. 

Now, the 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 characteristics as well as the physical properties of an EPDM resin for a given Mooney viscosity depend on the combination of the polymer’s molecular weight and long chain branching distributions. In this paper, we explore the effect of long chain branching on the mixing and processing of EPDM, and how defined long chain branching architectures enables the access to a complete spectra of Mooney-molecular weight relationships beyond the traditional relationships for linear polymers.